alkaline distillation problem.pdf

Hindawi Publishing CorporationInternational Journal of Chemical EngineeringVolume 2013 Article ID 719607 21 pageshttpdxdoiorg1011552013719607

Review ArticleChemical Pretreatment Methods for the Production ofCellulosic Ethanol Technologies and Innovations

Edem Cudjoe Bensah123 and Moses Mensah2

1 Department of Chemical Engineering Kumasi Polytechnic PO Box 854 Kumasi Ghana2Department of Chemical Engineering Kwame Nkrumah University of Science and Technology Private Mail BagUniversity Post Office KNUST Kumasi Ghana

3 Centre for Energy Environment and Sustainable Development (CEESD) PO Box FN793 Kumasi Ghana

Correspondence should be addressed to Edem Cudjoe Bensah edembensahgmailcom

Received 4 June 2013 Accepted 27 August 2013

Academic Editor Jose C Merchuk

Copyright copy 2013 E C Bensah and M MensahThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

Pretreatment of lignocellulose has received considerable research globally due to its influence on the technical economicand environmental sustainability of cellulosic ethanol production Some of the most promising pretreatment methods requirethe application of chemicals such as acids alkali salts oxidants and solvents Thus advances in research have enabled thedevelopment and integration of chemical-based pretreatment into proprietary ethanol production technologies in several pilot anddemonstration plants globally with potential to scale-up to commercial levels This paper reviews known and emerging chemicalpretreatment methods highlighting recent findings and process innovations developed to offset inherent challenges via a rangeof interventions notably the combination of chemical pretreatment with other methods to improve carbohydrate preservationreduce formation of degradation products achieve high sugar yields at mild reaction conditions reduce solvent loads and enzymedose reduce waste generation and improve recovery of biomass components in pure forms The use of chemicals such as ionicliquids NMMO and sulphite are promising once challenges in solvent recovery are overcome For developing countries alkali-based methods are relatively easy to deploy in decentralized low-tech systems owing to advantages such as the requirement ofsimple reactors and the ease of operation

1 Introduction

Cellulosic or second generation (2G) bioethanol is producedfrom lignocellulosic biomass (LB) in three main stepspretreatment hydrolysis and fermentation Pretreatmentinvolves the use of physical processes (eg size reductionsteamingboiling ultrasonication and popping) chemicalmethods (eg acids bases salts and solvents) physico-chemical processes (eg liquid hot water and ammoniumfibre explosion or AFEX) biological methods (eg white-rotbrown-rot fungi and bacteria) and several combinationsthereof to fractionate the lignocellulose into its componentsIt results in the disruption of the lignin seal to increaseenzyme access to holocellulose [1 2] reduction of cellulosecrystallinity [3 4] and increase in the surface area [5 6] andporosity [7 8] of pretreated substrates resulting in increased

hydrolysis rate In hydrolysis cellulose and hemicelluloses arebroken down into monomeric sugars via addition of acidsor enzymes such as cellulase Enzymatic hydrolysis offersadvantages over acids such as low energy consumption dueto the mild process requirements high sugar yields and nounwantedwastes Enzymatic hydrolysis of cellulose is affectedby properties of the substrate such as porosity cellulose fibrecrystallinity and degree of polymerization as well as ligninand hemicellulose content [9 10] optimum mixing [11]substrate and end-product concentration enzyme activityreaction conditions such as pH and temperature [12 13] Thecost of commercial enzymes is a major economic headachein 2G bioethanol production and such pretreatmentmethodsthat support low enzyme dosages per unit biomass whileoptimizing ethanol yields (in addition to other favourablefactors) are of interest in cellulosic ethanol production It is

2 International Journal of Chemical Engineering

known that cellulase loadings of less than 10 FPUgram-cellulose are essential for economic production of cellulosicethanol [14]

In fermentation sugars are converted into ethanol underliquid- or solid-state using yeast or bacteria The processeconomics is improved significantly if both C5 and C6sugars are utilized though the fermentation efficiency of C5sugars is very low Further the yeasts cannot endure lowpH as well as high ethanol and byproduct concentrations[15] Additional challenges with xylose fermenting yeastsinclude long fermentation periods low productivity highviscosity of fermentation broth and byproduct formation[15] For both enzymatic hydrolysis and fermentation thepresence of degradation compounds such as furfural andhydroxymethyl-furfural (HMF) produced during pretreat-ment inhibits the smooth functioning of enzymes Thusongoing research under pretreatment has focussed on thedevelopment of innovativemethods requiring the use of mildconditions that significantly reduce inhibitor formationwhilemaintaining high sugar yields

In general pretreatment presents the most practicaland economic challenges in the attempt to commercializecellulosic bioethanol [16ndash18] since it may affect upstream [14]as well as downstream processes by determining fermenta-tion toxicity enzymatic hydrolysis rates enzyme loadingsproduct concentrations and purification waste treatmentdemands and power generation [19] The results from manystudies have shown that pretreatment is relatively costlyamong the various operations and processes involved incellulosic ethanol production [20ndash25] representing about20 of the total cost [14] While pretreatment introducesadditional cost the consequence of hydrolysing lignocellu-lose without pretreatment is far less favourable since onlyabout 20 of native biomass is hydrolysed [26]

It is generally accepted that efficient pretreatment shouldavoid size reduction and use of costly chemicals [19 27]improve fibre reactivity and maximize formationrecoveryof sugars [28] avoid loss of carbohydrate [29] avoid for-mation of enzyme-inhibiting byproducts [30 31] preservecellulose and hemicellulose fractions that are easily digestibleby hydrolytic enzymes [32 33] generate high-value lignincoproduct [18 26] minimize energy requirement [22 34]and achieve high sugar yields under high biomass loads[35] However no perfect pretreatment method has beendiscovered since there are variations in terms of suitability ofonemethod for variousmaterials whichmay be further com-pounded by factors such as maturity mode of harvest extentof drying and storage conditions of the feedstock [36ndash39]The chemicalmethods of pretreating lignocellulosicmaterialsare widely employed in many pilot and demonstration plantssince they are ideal for low lignin materials This paperreviews the various chemical methods that have receivedsignificant attention globally with emphasis on process inno-vations and interesting findings from the work of researchersin the field It is the second of two papers (with the firstarticle addressing physical and physicochemical methods)that is expected to serve as a reference for researchers in bothacademia and industry The methods discussed are centredon the use of acids bases oxidants and solvents

2 Chemical Pretreatment ofLignocellulosic Biomass

21 Acid Hydrolysis In this method dried biomass is milled(occasionally) presoaked in water and submerged in acidicsolution under specific temperatures for a period of timePretreated content is filtered to separate the liquor from theunhydrolysed solid substrate which undergoes washing (toextract sugars and remove acids) andor neutralization beforesaccharification Generally the hydrogen ion concentrationis directly correlated with the hydrolysis reaction constantthus the more negative the pKa value of the acid the moreeffective the hydrolysis process [40] Sulphuric (H

2SO4) and

phosphoric (H3PO4) acids are widely used since they are

relatively cheap and efficient in hydrolysing lignocellulosethough the latter gives a milder effect and is more benignto the environment Hydrochloric (HCl) acid is more volatileand easier to recover and attacks biomass better than H

2SO4

[41] similarly nitric acid (HNO3) possesses good cellulose-

to-sugar conversion rates [42] However both acids areexpensive compared to sulphuric acid

In acidic media the amorphous hemicelluloses in LBhydrolyse quicker (than cellulose) to soluble sugars [4344] and some oligomers especially in mild conditions [21]through the disruption of xylosidic bonds and cleavage ofacetyl ester groups [45 46] and the lignin seal is degradedthrough substitution reactions and broken links accom-panied by condensation reactions that prevent dissolution[47 48] Cellulose undergoes preferential degradation ofamorphous regions leading to enlarged cellulose fibrils andfibril aggregates [44] and an increase in the crystallinity indexof the pretreated material [38 43]

The process is generally affected by particle size temper-ature reaction time acid concentration and liquid-to-solidratio The combined severity factor (1198771015840

0) is an index used to

assess the effect of pretreatment temperature time and pHon the efficiency of the process as shown below [49]

log11987710158400= log (119905 sdot 119890(119879minus100)1475) minus pH (1)

where 119905 is the reaction time inminutes and119879 is the hydrolysistemperature in ∘C Acid pretreatment comes under two mainvariationsmdashdilute and concentrated acid hydrolysis eachapplied under further process variations

211 Dilute Acid Pretreatment Under dilute acid (02ndash25ww) processes high temperatures (120ndash210∘C) and pressuresare used to achieve reaction times in seconds or minutes andare thus suitable for continuous operations [21 50] The lowacid consumption is a major advantage in terms of cost andprocess severity [51]Moreover low acid concentrations (lt1wv sulphuricphosphoric) release essential nutrients (S andP) that enhance downstream fermentation [52] A variationof the process involves two stages of pretreatment in thefirst stage most hemicelluloses in the biomass substrate aresolubilised in the presence of a more dilute acid while thesecond stage involves the use of a higher acid concentrationto hydrolyse the cellulose and the remaining hemicellulose[53 54]

International Journal of Chemical Engineering 3

Increasing pretreatment severity generally leads to higherrates of cellulose conversion to glucose at shorter reactiontimes though conditions that yield high glucose do notnecessarily translate to high xylose yields Pretreatment ofmunicipal solid waste (carrot and potato peelings grassnewspaper and crap paper) with dilute acid H

2SO4 HNO

3

and HCl was undertaken by Li et al [55] who found theglucose yield of pretreated substrates to dependmore on acidconcentration and enzyme loading than reaction tempera-ture For feedstock mixtures such as aspen and switchgrassand aspen and balsam the process was observed to haveno synergistic or antagonistic effect on enzymatic hydroly-sis indicating the likelihood of predicting such combinedsystems based on models for pure species yields [56] Acomparatively low number of researchers have investigatedthe nitric acid pretreatment of LB Dilute HNO

3pretreat-

ment was found to give the highest glucose concentration(compared to dilute H

2SO4) in the pretreatment of rye straw

[57] However byproducts from nitric acid pretreatment aredifficult to remove by washing of the pretreated substrates[42]

Also dilute H3PO4is frequently used the acid was

applied on potato peels with overall sugar yield reaching825 of the theoretical even though arabinose conversionwas found to be low due to its thermal instability [58]Its application to bamboo and corn cob also yielded highsugars at 170∘C for 45 minutes [59] and 140∘C for 10 minutesrespectively [60] In another work Avci et al [61] achieved85 glucose and 914 xylose yields on corn stover at 05(vv)180∘C15min and 1 (vv)160∘C10 respectively atlow concentrations of degradation products In an attemptto improve process performance researchers have triedcombinations of acids and other compounds with mixedresults Heredia-Olea et al [62] combined HCl and H

2SO4

in pretreating sweet sorghum bagasse but did not recordany significant improvement over acid treatment HoweverZhang et al [52] recorded higher xylose yields during com-bined (H

2SO4H3PO4) pretreatment of oil palm empty fruit

bunch compared to single acid application Anaerobic storageof pretreated substrates was found to improve enzymaticdegradability of reed canarygrass and switchgrass in a pilot-scale plant [63]

Asidemineral acids organic acids such asmaleic fumaric[8] and oxalic [64ndash67] have been found to be usefulsubstitutes to mineral acids Oxalic and maleic acids havehigher solution potential and degrade hemicelluloses moreefficiently than sulphuric acid [8] In addition they have twopKa values which favour efficient hydrolysis over a range oftemperatures and pH values [66 68] The use of maleic andfumaric generally results in lower degradations products atsimilar conditions compared to sulphuric acid [69] Oxalicacid application to corn stover gave best results at 160∘C for 10minutes at a concentration of 200mM [70] On maple woodoxalic pretreatment resulted in equivalent glucose (877)xylose (869) and total sugar yields (874) compared todilute sulphuric and hydrochloric acids [71]

Main Disadvantages Though dilute acid pretreatment hasreceivedwide attention from researchers due to its advantages

such as high cellulose content of pretreated substrates andlow requirement of enzymes it comes with some drawbacksA major demerit of this process is its requirement of spe-cial corrosion-resistant reactors which are usually expen-sive both in investment and operation [72] compared toother chemical (eg dilute alkali) and physicochemical (egsteam explosion and AFEX) methods [13 73] The energyconsumption of the process and the cost of the acid [74]as well as performance limitations based on particle size (afew millimetres) and solids concentration (le30) contributesignificantly to the overall cost [14] Dilute acids are lesseffective in removing lignin compared to alkaline methodsNeutralization of pretreated contents creates solid waste[75] though it is necessary for improving the downstreamfermentation process

The sugar yield is reduced because a portion of thesugar is degraded into enzyme-inhibiting byproducts suchas furfural (2-furaldehyde) 5-hydroxymethylfurfural (5-HMF) acetic acid gypsum vanillin and aldehydes (4-hydroxybenzaldehyde syringaldehyde etc) as a result of theconditions that cause cellulose to rapidly break into sugars[76ndash79] It is pertinent that inhibitors are removed by filteringoff hydroxylate liquor followed by washing and drying ofcellulose-rich residues [80] or by using reverse osmosis toexclude acetic acid furfural 5-HMF and other compoundsbefore fermentation [81 82]The use of membranes to detox-ify hydroxylates could be exploited at the industrial level dueto the ease of scaling up for large-scale operations Furtheremploying simultaneous saccharification and fermentation(SSF) ensures rapid conversion of glucose into ethanol andthe continuous removal of ethanol during fermentation [83]Other options pertain to the use of agents such as activatedcarbon to selectively absorb inhibitors [84] or the use of yeaststrains that tolerate inhibitors at significant high levels [85]

Another compound known to cause inhibition of enzy-matic hydrolysis of cellulose is pseudoligninmdashan acid-insoluble substance that is formed from repolymerizationof degradation products withwithout lignin Surface ligninreduces cellulase affinity for biomass substrate and lowers thehydrolysis rate [86] High acid concentrations temperaturesand treatment time generally create conditions for increaseddegradation products and pseudolignin resulting in reducedlignin recovery in the hydroxylate Inhibitor concentrationsmay be reduced by combining mild physical-chemical con-ditions and optimised enzyme loadings [87] by using a two-stage process [53] or by performing deacetylation prior topretreatment to reduce hydroxylate toxicity [45] Losses inC5 sugars solubilised into the liquid stream are avoided ifit is further processed [33] or if unfiltered hydroxylates arewholly used in enzymatic hydrolysis where neutralization ofthe hydroxylate can be achieved by the use of a novel single-step neutralization and buffering procedure to adjust the pH[87 88]

212 Concentrated Acid Pretreatment This pretreatmentvariation uses concentrated sulphuric (65ndash86 wv)hydrochloric (41) or phosphoric (85 ww) acids topretreat dried (5ndash10 moisture) pulverized biomass at lowtemperatures (30ndash60∘C) and pressures Pretreated contents


are diluted with deionized water for saccharification totake place at moderate temperatures (70ndash121∘C) separatedinto solid and liquid fractions followed by washing andneutralization of the solid substrates [89 90] Anothervariation involves the addition of organic solvents such asacetone to pretreated contents followed by agitation of themixture to stop the reaction and to separate the solids fromthe supernatant (containing lignin) which undergo furtherwashing before enzymatic hydrolysis [91]

The efficiency of the process is affected by acid concen-tration acidbiomass ratio process temperature and timeTwo patented process configurationsmdashthe Arkenol and theBiosulfurol processesmdashwhich are based on the concen-trated H

2SO4platform have shown potential commercially

The Arkenol process involves pretreatment (decrystalliza-tion of biomass) at temperatures below 50∘C at acid (70ndash77)biomass (10 moisture lt1mm particle size) ratio of125 [92] In the Biosulfurol process the biomass is trickled inthe acid (70) in the presence of dry CO

2from the fermenter

followed by dilution of the pretreated slurry with water Theacid is partly separated from the biomass slurry by the use ofmembranes before fermentation and partly in an anaerobicdigester after fermentation The relative merits of the Biosul-furol process according to vanGroenestijn et al [92] includethe nonrequirement of enzymes low temperature treatmentlow production of degradation products and the capacity tofractionate various biomass with high ethanol yields

Concentrated H3PO4is effective at low temperatures

dissolves cellulose in the presence of water possesses noinhibitory effects on hydrolysis and fermentation and giveshigh sugars [93] compared to dilute acid pretreatment [89]Pretreated biomass substrates are left with uneven and roughmolecular surfaces that enhance enzyme adsorption rates andthereby accelerate hydrolysis [94] Combinations of acid andp-cresol a phenol derivative enabled complete separationof lignin and carbohydrates in the pretreatment of oil palmempty fruit bunch [90] In cellulose solvent- and organicsolvent-based lignocelluloses fractionation (COSLIF) thebiomass feedstock is fractionated by adding concentratedH3PO4under mild conditions (50∘C 1 atm and 60min)

followed by the addition of an organic solvent such as ethanol(95 vv) or acetone under room temperature for 10min [9596] The main advantages of COSLIF include high enzymeaccessibility to cellulose in pretreated substrates [96] andeffective fractionation of diverse biomass with good sugaryields [95] High glucan digestibility at low enzyme dose isusually achieved with COSLIF [96 97] and in combinationwith other agents such as ionic liquids [97]

Despite the aforementioned merits COSLIF (like otherconcentrated acid methods) is slow and uses high loads ofsolvent Further depolymerisation and sugar degradationincrease at temperatures above 50∘C [95] Other challengeswith concentrated acid pretreatment include corrosion ofequipment acid recovery and neutralizationwaste when acidis not recovered

22 Alkali Pretreatment

221 Process Background In alkaline pretreatment ligno-cellulosic materials are mixed with bases such as sodium

potassium calcium and ammonia [50 98] at specific temper-atures and pressures in order to degrade ester and glycosidicside chains of the material [18] leading to lignin structuredisruption [99 100] cellulose swelling and decrystalliza-tion [74] Alkaline treatment extracts hemicelluloses frompolysaccharides and produces organic acids that lower thepH Two streams are formed comprising a wet solid fractioncomposed ofmainly cellulose and a liquid fraction containingdissolved hemicelluloses lignin and some unreacted inor-ganic chemicals The solids are separated and washed inwarmhot water until neutrality before they are hydrolysedWashing removes enzyme inhibitors and residual unreactedreagents and improves the release of sugars from pretreatedsolids

The process is influenced by NaOH loading liquid-to-solid ratio temperature and time among others In generalpretreatment is less severe since it can be carried out underatmospheric conditions though at the cost of longer reten-tion times [50 101] Low alkali concentrations (lt4 ww)are mostly used at high temperatures and pressures Mildalkali pretreatment of biomass favours enzymatic hydrolysisespecially formaterials that have relatively low lignin contentSugar degradation and corrosion problems are less severe inalkali processes than in acid pretreatment [57 102] and mildconditions (55∘C) may not require posttreatment washingsince enzyme inhibiting compounds are generally low [103]

Bases that have been used widely include hydroxides ofpotassium sodium and calcium as well as sodium carbonate(Na2CO3) KOH selectively removes xylan [104] as was

observed on peashrub at 25∘C for 10 h with high efficiency[105] Application of KOH pretreatment on rye straw gavelower sugar yields than dilute acid [57] It was however foundto give high fermentation efficiency relative to other methods[42] Regarding Na

2CO3 efficient delignification of biomass

is realized which makes the carbonate a promising chemicalfor pretreatment Application of the carbonate [106] as wellas combined Na

2CO3-Na2SO3[107] on rice straw recorded

good carbohydrate preservation and sugar yieldsThe basesmdashNaOH and Ca(OH)

2mdashhave been extensively

investigated as agents for pretreatment and are discussed inthe sections below

222 Sodium Hydroxide Pretreatment Though expensivesodium hydroxide (NaOH) is used widely due to its relativehigh alkalinity for the fractionation of various materialsincluding agricultural residues and wood Dilute NaOHapplication loosens the biomass structure separate the bondsbetween the lignin and the carbohydrates increases theinternal surface area decreases the degree of polymerizationand crystallinity and disrupts the lignin structure [108]Homogenization of pretreated substrates enhances glucoseyields by increasing the surface area and porosity of thebiomass [6] High alkaline concentrations generally causeincreased biomass delignification [109] though severe con-centrations (6ndash20 ww) result in cellulose dissolution andreduced lignin removal [110] Pedersen et al [33] observedthat increasing the pH from 10 to 13 increased the removal oflignin from 40 to 80 ww dry wheat straw at 140∘C Alsoby varying the NaOH loading rate from 3 to 9 based on


initial dry bagasse Zhao et al [111] recorded an increase indelignification from 523 to 755

Compared to acid hydrolysis NaOH pretreatmentappears to improve enzymatic biodegradability due to thehigher delignification ability of alkali Evidence of thisassertion for example can be found in the work of Ioelovichand Morag [112] who applied both dilute H

2SO4and NaOH

to four materials and found the alkali to be more efficient interms of sugar yields delignification and biomass utilizationrate

In many situations positive results have come out fromcombined NaOH and other agents such us peracetic acid[111] polyelectrolyte [113] and hydrogen peroxide In addi-tion the environmental impact is low and no special reactorsare required As a pretreatment agent alkaline peroxidefavours enzymatic hydrolysis as it removes lignin efficiently[114] and produces insignificant inhibitors [115 116] Itsapplication to corn stover was effective in producing goodglucose yields at low (0125 g H

2O2g biomass) peroxide

doses [117] Further higher sugar yields from grass stoverswere obtained using peroxide relative to dilute NaOH andAFEX [118] Another positive aspect about peroxide is its usein recovering lignin and other components from substratespretreated by other methods which results in higher sugaryields [116]

223 Lime Pretreatment Limemdashin the form of quick limeCaO and slaked lime Ca(OH)

2mdashhas also been extensively

investigated as a pretreatment agent due to its low costsafety in handling availability in many countries and easeof recovery In pretreatment lime and water are addedto the feedstock at temperatures ranging from ambient to130∘C sometimes in the presence of oxygen to enhancedelignification [21 119] A loading of 01 gramof slake lime pergramof biogas is common andprocess time varies fromhoursto weeks [26] Lime improves hydrolysis rates of biomass byremoving acetyl groups and a considerable portion of thelignin fraction [120] reducing counter-productive cellulaseadsorption [14] and formation of degradation byproducts[121] and promoting cellulose accessibility [122]

Lime has been applied on various feedstocks with encour-aging results Lignin was selectively removed at low car-bohydrate losses in the treatment of sugarcane bagasse atoptimised conditions of 90∘C for 90 h at lime loading of04 gg bagasse [123] Lime application to feedstocks such asinter alia corn stover [124] switchgrass [125] and sugarcanebagasse [126] gave high carbohydrate conversions to simplesugars Combined lime and oxidants so far have shownpositive results [119] and further investigations are neededThe ease with which lime can be recoveredmdashvia precipitationto CaCO

3using CO

2mdashis a major advantage The carbonate

may be combusted alongside with lignin and other residuesin a boiler to ash and CaO which can be mixed with waterand slaked to form Ca(OH)

2[21]

Despite the merits of lime pretreatment its use facesdrawbacks such as longer reaction period (influenced bythe reaction temperature) compared to NaOH under similarconditionsMoreover it dissolves in water at a slower rate andthus requires higher volumes of water for pretreatment In

some instances lime pretreatment produced substrates withless favourable characteristics for example lime pretreatedsugarcane grass was less amenable to cellulose hydrolysiscompared to dilute acid [78]

224 General Drawbacks of Alkaline Methods Alkaline pre-treatment is generally unsuitable for woody biomass due tothe requirement of severe conditions needed to fractionaterecalcitrant woodThus lignin removal may be improved viamethods that include oxygenation [19] and the addition ofchemicals such as urea [108] Other drawbacks are the loss ofhemicelluloses and the formation of inhibitors at harsh con-ditions Further the formation of salts upon neutralizationof pretreated contents may present challenges with disposalSalts hamper the purification of pretreated hydroxylates [127]while posttreatment washing results in sugar losses [103]Higher catalyst loadings are generally used and thus requirerecovery and reuse to improve process economics in anindustrial scale plant [128]

23 Wet Oxidation (WO)

231 Process Description In WO biomass undergoes oxi-dation in an aqueous (acidic neutral and alkaline condi-tions) solution via reaction with oxygen (air) at elevatedtemperatures (125ndash315∘C) and pressures (05ndash5MPa) [54129] The pretreated suspension is filtered to separate thecellulose-rich solid from the hemicellulose-rich filtrate andthe solid component is washed with deionized water beforeundergoing enzymatic hydrolysis WO pretreatment oxidizesthe hemicellulose fractions of materials into intermediatessuch as carboxylic acidsmdashvia peeling reactions and chaincleavage and from the phenolic structures of lignin [130]acetaldehydes and alcohols and finally to CO

2and H

2O

[131] The degree of fractionation in most cases is influ-enced by the reaction temperature more than the time andoxygen dose [138] High temperatures pressures pH andcatalysts favour rapid oxidation [129] the catalysts furthercause increases in the acid (formic and oxalic) concentrationregardless of the reaction temperature [130]

Generally alkalineWO reduces the formation of enzyme-inhibiting compounds such as furfural and HMF comparedto acidic and neutral conditions [132 133] High phenolicconcentrations reduce the volumetric productivity of theenzyme [134] by causing partition and loss of integrityof cell membranes of the fermenting organisms and arethus more toxic than HMF and furfural [7] Reports fromseveral researchers indicate that wet oxidation achieves goodhydrolysis and fermentation yields from various LB notablyspruce [130 131] wheat straw [134] rape straw [135] and ricehusk [136] Under optimized conditions of 185∘C 5 bar and15min about 67of cellulose in the solid fraction of rice huskwas obtained while 89 and 70 of lignin and hemicelluloseswere removed [136] WO pretreatment (195∘C 15min 12bar 2 gL Na

2CO3) and subsequent enzymatic hydrolysis of

winter rye oilseed rape and faba bean produced ethanolyields of 66 70 and 52 of the theoretical respectively[137]


232 Drawbacks WO is costly to operate owing to the needto supply high pressure oxygen and chemicals such as sodiumcarbonate [138] It appears that alkaline WO does not favourwoods as was observed in the pretreatment of spruce [131]and willow [133] where optimized conditions were found at12 bar and 200∘C in 10min and 185∘C 12 bar O

2 15min

respectively under neutral conditions One potential optionfor reducing cost is to use air instead of oxygen in a modifiedprocess known as wet air oxidation (WAO) as was employedfor the pretreatment of shea-tree sawdust [139] resulting inmaximum sugar yield of 2635mg glucoseg dry biomassat optimum conditions of 150∘C45min1 H

2O210 bar air

[140]

24 Organosolv Pretreatment

241 Process Description The organosolv process involvesthe addition of an (aqueous) organic solvent mixturewithwithout a catalystmdashsuch as an acid (HCl H

2SO4 etc)

a base (eg NaOH) or a salt (MgCl2 Fe2(SO4)3 etc)mdashto

the biomass under specific temperatures and pressures [13141 142] The process produces three main fractionsmdasha highpurity lignin a hemicellulosic syrup containing C5 and C6sugars and a relatively pure cellulose fractionThe pretreatedsolid residues are separated by filtration and washed withdistilled water to remove solvents and degradation productswhich may possess inhibitory characteristics to downstreamprocess such as enzymatic hydrolysis and fermentationPretreatment conditions lead to simultaneous hydrolysis andlignin removal [74] via the disruption of internal bonds inlignin lignin-hemicellulose bonds and glycosidic bonds inhemicelluloses and to a smaller extent in cellulose [142]Other changes include the formation of droplets of lignin onthe surface of pretreated biomass a situation that inhibitshydrolysis by adsorption on the surface of the cellulose[143] Process variables such as temperature reaction timesolvent concentration and acid dose affect the physicalcharacteristics (crystallinity degree of polymerization of cel-lulose and fibre length) of the pretreated substrates In mostsituations high temperatures and acid concentrations as wellas elongated reaction times cause considerable degradation ofsugar into fermentation inhibitors

Though sulphuric acid has been used extensively as acatalyst due to its strong reactivity it is toxic and corrosiveand possesses inhibitory characteristics [144] Park et al [144]evaluated the effectiveness of acidic (H

2SO4) basic (NaOH)

and neutral (MgCl2) catalysts on pine and found the acid

as the most efficient in terms of the ethanol yield howeveran increase in the concentration of the base from 1 to 2had a positive effect on digestibility Organic solventsacidsthat have been used as catalysts include formic oxalic acetyl-salicylic salicylic acid methanol ethanol acetone ethyleneglycol triethylene glycol and tetrahydrofurfuryl alcohol [13145ndash147]The use of CO

2as a catalyst did not improve process

yields on pretreatment of willow wood [151]

242 Process Variations Organosolv pretreatment comes inseveral variations based on the solvent type catalyst and

process conditions The Battelle organosolv method involvesthe use of a ternary mixture of phenol water and HClto fractionate the biomass at about 100∘C and at 1 atm[148] The acid depolymerizes lignin and hydrolyses thehemicellulose fraction and the lignin dissolves in the organicphase (phenol) while the monosaccharides are attracted tothe aqueous phase upon cooling of the fractionated biomass

Similarly the formic acid organosolv process (formasolv)involves the application of formic acid water and HCl todepolymerize oxidize and dissolve lignin hemicelluloseand extractives in the biomass and the precipitation of thelignin is achieved by the addition of water [148] Formicacid has a good lignin solvency and the process can beundertaken under low temperatures and at atmosphericpressure [147] However formic acid may cause formylationof the pretreated substrates which could reduce cellulosedigestibility Pretreated substrates can be deformylated inalkaline solution as was observed on bagasse at 120∘C [147]Formic acid (5ndash10ww no catalysts) was used byKupiainenet al [149] on delignified wheat straw pulp at 180ndash220∘Cyielding a maximum glucose yield of 40

Organosolv pretreatmentwith acetic acid (acetosolv) pro-duces higher yields than formic since lessmass is dissolved fora given time In addition acetosolv achieves higher celluloseviscosity in smaller time periods [148]

The use of ethanol in organosolv pretreatment (ethano-solv) enables the recovery of high value products includ-ing cellulose sulphur- and chlorine-free lignin enrichedhemicelluloses and extractives Further purification may beachieved via the use of solvents such as ionic liquids [127]Unlike formasolv the ethanosolv process is usually oper-ated under higher pressures and temperatures In additionreprecipitation of lignin occurs due to lower lignin solubility[147] The reduced toxicity of ethanolmdashcompared to solventssuch as methanolmdashto the downstream fermentation processand the fact that ethanol is the final product are additionalbenefits [142 150] Generally lower ethanolwater ratiosfavour hemicellulose hydrolysis and enzymatic degradabilityof pretreated substrates [151] since ethanol is an inhibitor tothe performance of hydrolytic enzymes Ethanosolv has beenexplored for the development of proprietary technologiessuch as the Alcell process which is a sustainable alternativeto kraft pulping [152] and the Lignol processmdasha biorefineryplatform that uses aqueous ethanol (50ww) for pretreatingLB at 200∘C and 400 psi to separate the various componentsin woody biomass [153 154] High sugar yields and productrecovery have been observed on ethanosolv pretreatmentof various materials including hybrid poplar [155] andJapanese cypress [156] A major advantage is the potentialto recover much of the ethanol [143 157] and water [141]which reduces the operating cost Ethanosolv coproductssuch as hemicellulose syrup and lignin can serve as feedstocksfor the production of high value biochemicals Moreoverethanosolv lignins whose functional groups and molecularweight depend on process conditions are known to possessantioxidant properties [158]

In several situations presoakingmaterials for example inacidicmedium [159] or in bioslurry [160] positively affect theprocess in terms of sugar yields and lignin removal among


others Other variations involve the combined use of acid andbasic catalysts [146] microwave-assisted organosolv [161]and the avoidance of catalysts [162] In another variationthe biomass is treated with the inclusion of ferric sulphateand sodium hydroxide to the biomassliquor (formic acidand hydrogen peroxide) mixture Formic acid reacts withhydrogen peroxide to produce peroxyformic acid and itsapplication in organosolv pretreatment (Milox) of biomassproduced good results on both hardwoods and softwoods[148]

243 Drawbacks Though organosolv is promising due to thepotential to obtain byproducts in pure forms for the manu-facture of high-value biochemicals the process is generallycostly to operate due to the requirement of high temperaturesand pressures The use of mineral acids in the organosolvprocess is an environmental concern and corrosion due tothe use of organic acids is a challenge In addition pretreatedsubstrates need washing to prevent lignin from precipitatingand recovery of expensive volatile organic solvents needs veryefficient control systems and additional energy requirements[163]

25 Ionic Liquids (Green Solvents)

251 Properties of Ionic Liquids Ionic liquids (ILs) are saltsconsisting of large cations (mostly organic) and small anions(mostly inorganic) with a low degree of cationic symmetryand a melting point below 100∘C ILs are nonflammable [14]are liquid at room temperature [164] and are known toimprove antielectrostatic and fire-proof properties of wood[165] They have low volatility and high thermal stability[14] up to temperatures of about 300∘C [166] high electricalconductivity high solvating properties and wide electricalwindow [167] Other favourable aspects involve character-istics such as water stability polarity refractive index anddensity [168]

Ionic liquids exist in two main formsmdashsimple saltscomprising single cations and anions and those where equi-librium is involved [50] The most common forms containthe imidazolium cation which can pair with anions suchas chloride bromide acetate sulphate nitrate methanoateand triflate ILs could be designed and developed to pretreatspecific biomass under optimal conditions by combiningcations and anions which can result in an estimated for-mulation of 109 ILs [169] For example the ILs 1-ethyl-3-methylimidazolium glycinate (Emim-Gly) and 1-allyl-3-methylimidazolium chloride (Amim-Cl) were synthesizedfrom various compounds for the dissolution of bamboo [170]and wood [71] respectively In addition the properties of ILscould be altered by varying the length and branching of thealkyl groups that are integrated into the cation [171]

Not all characteristics of ionic liquids are favourable assolvents in pretreatment For example chloride-based ILssuch as 1-butyl-3-methylimidazolium chloride (Bmim-Cl)are toxic corrosive and very hygroscopic while others suchas Amim-Cl are viscous with reactive side chains [172] AlsoILs with long akyl chains have the tendency to obstruct

nonpolar active sites of enzymes due to their hydrophobicnature [173] Others have favourable properties and have thusbeen under intense investigation as promising solvents Forexample phosphate-based solvents possess higher thermalstability and lower viscosity and toxicity than chloride-basedones [167] Positive outcomes have also been recorded withthe use of 1-ethyl-3-methylimidazolium acetate (Emim-Ac)since it is favourable to in situ enzymatic saccharification dueto its biocompatibility and enzymatic activity [174]

252 Process Description and Mechanism In IL pretreat-ment a mixture of the biomass (01ndash05mm) and thesolventmdashsometimes in the presence of water and acidmdashisincubated at temperatures ranging from 80 to 160∘C for 10minutes to 24 hours followed by the addition of an antisol-vent to precipitate the cellulose fraction In acidic conditionsbiomass dissolution is followed by acid hydrolysis of dissolvedcellulose [175] The pretreated supernatant is removed viacentrifugation or filtration and the cellulose is washed withdistilled water lyophilized (freeze-dried) and saccharifiedThe antisolvent is separated from the IL by processes such asflash distillation as the IL is recovered for reuse ILs convertcarbohydrates in lignocellulosic materials into fermentablesugars via two main pathways one is the pretreatment ofthe biomass to improve its enzymatic hydrolysis efficiencyand the other focuses on the transformation of the hydrolysisprocess from a heterogeneous to a homogeneous reactionsystem by dissolution in the solvent [176]

Both the cation and the anion function differently inthe dissolution of biomass [169] The effectiveness of pre-treatment is predicted using the Kamlet-Taft hydrogen bondacceptor ability 120573 usually the higher values of 120573 translateto higher lignin removal and vice versa [177] It is knownthat component ions in ILs influence enzyme activity [178]and stability [173] and the anionmdashas a result of its hydrogenbasicitymdashattacks and breaks the hydrogen bonds of cellulosestructure [179] by forming hydrogen bonds with the cellulose[180] Thus the cellulose is solubilised and the crystallinenature is reduced [181] via cell wall swelling resulting fromdislocation of hydrogen bonds between cellulose fibrils andlignin [182] partial removal of hemicellulose and biomassdelignification [183]

The dissolved cellulose in IL-pretreated hydroxylate isprecipitated (regenerated) into cellulose II on addition ofanti-solvents such as water [182 184] methanol [184 185]acetone [186] and ethanol [166] via preferential solute-displacement mechanism The type of antisolvent was foundto have no effect on the structure of regenerated cellulosein the pretreatment of Avicel according to Dadi et al[185] Regenerated cellulose is more amorphous and hasadditional sites for enzyme adsorption which is favourableto saccharification Addition of water in the cause of IL-biomass reaction improves cellulose hydrolysis by increasingselectivity to glucose and cellobiose [187] If antisolventmixtures such as wateracetone are used then cellulose andlignin are distinctly separated through dissolution in waterand acetone respectively [170 188]

The temperature is a key parameter that influences sugarrelease pattern saccharification kinetics and sugar yields


[189] Higher temperatures and pretreatment times are moreefficient in solubilising lignin [190] From the work of Zhi-Guo and Hong-Zhang [191] nearly 100 increase in glucoseyield was recorded on pretreatment of wheat straw withAmim-Cl when the temperature was increased from 125 to150∘C at a reaction time of 2 h At ambient conditions a frac-tion cellulose I may remain and recrystallize to microfibrilsof cellulose I upon expulsion of the solvent [192]

253 Application ILs are increasingly being used to dissolvevarious LB as shown in Table 1 The effectiveness of the sol-vent depends partly on the type of biomass being pretreatedand the final application of pretreated substrates includingthe regenerated cellulose Carbohydrate losses are generallylow and degradation products are significant only at severeconditions Through the work of authors such as Cheng et al[193] Xie et al [172] Dadi et al [166] Hou et al [194] andothers it is known that significant sugar yields are achievedwithout the elimination of crystallinity

254 Drawbacks and Process Modifications Though theuse of ionic liquids is under consideration for large scaleapplications several challenges such as high solvent costhigh solvent loading technical challenges and cost of solventregeneration and inadequate knowledge on the impact ofionic liquids on the environmental [38 165 167] ILs withhigh viscosities have low potential in terms ofmass and phasetransfer which presents challenges in engineering applica-tions [165 175] Moreover the separation of hydrophilic ILsand monomeric sugars in water is difficult [178 204] SomeILs also exhibit tendencies to denature enzymes [168] andthe active sites of enzymes could be blocked by layers ofhydrophilic ILs decreasing or destroying the aqueous phasesurrounding enzyme surface [173] Washing of regeneratedcellulose as well as recycling of ILs via processes suchas evaporation and reverse osmosis is practically costlywhich presents challenges in the development of processtechnologies for the efficient use of ILs within a biorefineryWhile delignification increases with high temperatures suchconditions also cause hemicellulose losses as was observed inthe pretreatment of switchgrass and agave bagasse at 120 and160∘C [190]

In order to address some of the shortcomings of con-ventional IL pretreatment approach several process routesand configurations are being developed The use of lowerIL concentrations is realized by using aqueous ILs [175] orby undertaking both pretreatment and saccharification ina single unit followed by direct extraction of sugars whichavoids the need to wash regenerated cellulose Aqueous ILshave lower viscosities reduce recycling demands in terms ofcost and effectively deal with high biomass loadings [175]Emerging green solvents such as cholinium-based ILs havebeen found to be more biocompatible and renewable andlower in cost and with yields comparable to imidazolium-based ILs [198]

Economic improvements have been reported via inter-ventions such as the use of thermophilic cellulase in highsolvent concentrations [205] application of acid catalysts

such as sulfonated carbon materials (sugar catalysts) [206]HCl [175 187] andNafionNR50 [207] inclusion of chemicalssuch as NH

4OH-H

2O2[208] and electrolyte solution [181]

direct (without cellulase) conversion of pretreated substratesto biofuels in consolidated bioprocessing [209] the reuseof solvent in several batches [169] Notwithstanding otherprocess enhancements it is necessary that lignin-derivedproducts are efficiently utilized to improve process eco-nomics

26 Oxidizing Agents Unlike the methods discussed abovepretreatment involving the application of oxidizing agentshas received less attention among researchers partly due tothe high cost of the oxidants such as ozone and hydrogenperoxideThe sections below discuss oxidant-basedmethodshighlighting recent advances in research and process devel-opment

261 Ozonolysis In ozonolysis ozone is sparged into amixture of biomass and water at room temperature andspecific time periods leading to the solubilisation of ligninand hemicelluloses The focus of attack is on the aromaticring of lignin [7] and the process is affected by ozone con-centration biomass type andmoisture content and airozoneflow rate [210] Though the process is relatively expensivedue to large requirements of ozone the process comes withbenefits as follows high drymatter concentrations (45ndash60)effective removal of lignin very low production of inhibitoryproducts and reactions performed at atmospheric conditions[211 212] Ozone thus barely attacks carbohydrates [212]Lignin degradation products such as carboxylic acids thatmay form can be eliminated by washing with water at roomtemperature even though it comes at the expense of somecarbohydrates losses

In some instances ozone application to specific biomassresulted in low sugar yields In basic medium ozone appli-cation was found to be inefficient on wheat and rye straw[210] Ozone treatment of cotton stalk (10 wv) at 4∘C for30ndash90 minutes reduced lignin by 1197ndash166 at xylan andglucan solubilisation of 19ndash167 and 72ndash166 respectivelycomparatively NaOH treatment achieved higher delignifica-tion of 6563 [109] In another work high delignificationand low carbohydrate loss were observed when a two-stepmethod comprising ozone and ethanosolv was applied toSweetgum Miscanthus and Loblolly pine [213] In additioncombined ozonolysis and autohydrolysis offer benefits suchas high hemicellulose solubilisation high glucose and ethanolyields low use of chemicals and low waste production [213]

Recently the use of plasma-generated ozone (from air oroxygen-enriched air) at atmospheric conditions has attractedinterest among researchers including Schultz-Jensen andteam at the Risoslash National Laboratory for Sustainable Energyin Denmark [211] Employing a fixed-bed reactor a CO

2

detector and a technique for continuous determination ofozone consumption lignin degradation of ozone pretreat-ment of wheat straw was monitored in real time with respectto ozone consumption andCO

2emission Lignin degradation

of 1mm particles was found to be almost complete while that


Table 1 Application of ILs to selected biomass resources

Biomass Solvent Temperature (∘C) time (min) Reference

Eucalyptus Emim-Ac 150 3 [183]Amim-Cl 120 5 [184]

Poplar Emim-Ac 120 1 [195]Pine Amim-Cl 120 5 [184]Spruce Amim-Cl 120 5 [184]Energy cane bagasse Emim-Ac 120 05 [196]

Switchgrass Emim-Ac 160 3 [38]120ndash160 6 [190]

Bamboo Emim-Gly 120 8 [170]

Wheat straw Amim-Cl 100ndash150 2ndash6 [191]Bmim-Ac 100ndash150 017ndash1 [164]

Water hyacinth Bmim-Ac 100ndash150 017ndash1 [164]Rice husk Bmim-Cl Emim-Ac 100 10 [197]Rice straw Ch-Aa 90 2 [194]Kenaf powder Ch-Ac 110 16 h [198]Cassava pulp Emim-Ac Dmim-SO4 Emim-DePO4 25ndash120 24 [188]Dmim-SO4 1 3-Dimethylimidazoliummethyl sulphate Emim-DePO4 1-Ethyl-3-methylimidazolium diethyl phosphate Ch-Aa Cholinium amino acids Ch-Ac Cholinium acetate

of 2mm particles was less than 80 leaving a solid fractionmainly composed of carbohydrates Maximum glucose andethanol yields of 78 and 52 were observed after enzymatichydrolysis and SSF (based on glucan) respectively basedon optimal ozonisation for 1 h [214] The ethanol yield wasrelatively low and the process economics has the potential tobe improved via the recovery and use of lignin byproductsand hemicellulose as well as developing schemes to reduceozone consumption for similar yields

Aside high delignification and carbohydrate preservationpretreated substrates have shown potential for use in theproduction of enzymes by fungi such as Trichoderma reeseiwith lower titres of cellulases and higher amount of xylanasesrecorded from autoclave sterilization of pretreated materialscompared to nonsterilized substrates with antibiotics added[215]

262 Other Oxidizing Agents When exposed to biomassoxidants such as hydrogen peroxide (H

2O2) peracetic acid

(C2H4O3) sulphur trioxide (SO

3) and chlorine dioxide

(ClO2) solubilise hemicellulose and lignin under mild alka-

line or neutral conditionsThe pretreated biomass undergoesoxidative delignification due to the reaction of the aromaticring of lignin with the oxidizing agents leading to improveddigestibility compared to alkaline pretreatment only [7]Biomass degradability is affected by the type of biomassoxidant dose reaction temperature and time Among theoxidants hydrogen peroxide is the most studied Hydrogenperoxide degrades into hydrogen and oxygen and does notleave residues in the biomass [216] By pretreating waterhyacinth and lettuce with NaOH followed by H

2O2 Mishima

et al [217] recorded higher sugar yields compared to NaOHH2SO4 and hot water pretreatments under similar condi-

tions Process variations that have also produced high sugaryields include the addition of catalysts such as manganese

acetate [218] postpretreatment acid saccharification [216]and alkaline-peroxide application without postpretreatmentwashing [219]

Generally H2O2permits fractionation of biomass at

ambient pressures and low temperatures allowing the use oflow cost reactors Unfortunately the application of oxidizingagents produces soluble lignin compounds that inhibit theconversion of hemicelluloses and cellulose to ethanol Thereis also loss of sugar due to the occurrence of nonselectiveoxidation [7 104] In addition the high cost of oxidants is amajor limitation for scaling up to industrial levels

Recently the use of sulphur trioxide in a process calledsulphur trioxide microthermal explosion (STEX) has beenexplored to pretreat biomass such as rice straw [220] Biomassis hanged above a solution of oleum (50 SO

3) and NaOH

(1 wv) and swirled in a test tube at 50∘C1 atm for 7 hfollowed by washing to obtain the solids [220] The internalexplosion is believed to occur due to heat released fromSO3-straw reaction that causes rapid expansion of air and

water from the interior of the biomass resulting in enhancedstructural changes and pore volume [220] and partial removalof lignin and hemicellulose [221] Pretreatment of rice strawat the aforementioned conditions resulted in saccharificationyield of 91 [220] The efficient handling of SO

3will be

a challenge due its corrosiveness regarding this emergingpretreatment Another novel process involves the use ofchlorine dioxide (in the presence of aqueous ethanol) onbiomasswhich results in high fraction of glucose in pretreatedbiomass and low formation of inhibiting compounds [222]

27 Sulphite Pretreatment The sulphite process is a maturedtechnology that has been used in the pulp and paper industryfor decades and has been adapted to the pretreatment ofLB for enhanced enzymatic hydrolysis and fermentationto ethanol In this method milled biomass (lt6mm) is


mixed in sulphite (Na2SO3 NaHSO

3 etc) solution (1ndash10

ww) in acidic basic or neutral environments at selectedtemperatures (80ndash200∘C) and reaction times (30ndash180min)Pretreated solids are separated from the spent liquor byfiltration and the solids are washed with distilled water anddried before undergoing saccharification The process par-tially degrades and sulphonates lignin and enhances glucoseyields due to the formation of sulphonic andweak acid groupswhich improves the hydrophilicity of pretreated substrates[223] Sulphonation is enhanced in the presence of volatileorganic solvents such as ethanol which reduces the surfacetension thereby allowing effective solution penetration of thebiomass In addition the lignin is hydrolysed and dissolved inthe organic phase and is easily recovered in pure forms [223]Lignin removal can be accelerated further by the presenceof sulphomethyl groups produced from combined action ofsulphite and formaldehyde on lignin resulting in high sugaryields [224]

Sulphite application is emerging as a promising pretreat-ment due to positive results recorded from several materialsPretreatment of corn stover with alkaline Na

2SO3at 140∘C

resulted in 92 lignin removal and 782 total sugar yield(048 gg raw biomass) after enzymatic hydrolysis which washigher than four other alkali-based methods under similarconditions [225] About 793 of total glucan was convertedto glucose and cellobiose during corn cob pretreatment at156∘C 14 h 71 charge and solids loading of 1 76 ww andsubsequent SSF gave 722 theoretical ethanol yield [226] Inanother work pretreatment of corn cob residues producedthe highest glucose yields (812) in the presence of ethanolcompared to acidic basic and neutral conditions [223]

At the pilot level sulphite-based methods have beeninvestigated and demonstrated good results In a proprietaryprocess known as sulphite pretreatment to overcome recal-citrance of lignocellulose (SPORL) the biomass material isfirst pretreated with dilute solutions of sulphuric acid andsodium bisulphite (NaHSO

3) after which the residual solids

are separated from the hydroxylate The solids are then disc-milled and pressed to obtain solids moisture content of about30 [227] Lignin is sulphonated and partially removed andhemicellulose is nearly removed completely which favourssubsequent size reduction and enzymatic hydrolysis [228]The SPORL process has been effectively used to pretreat(180∘C 25min liquorwood = 3 1 vw) lodgepole pine forsubsequent conversion to ethanol at a yield of 276 Ltonwood and at a net energy output of 455GJton wood [227]SPORL pretreatment of switchgrass was superior to diluteacid [228 229] and alkali [228] in terms of the digestibilityof the pretreated substrates Similarly higher sugar yieldsand lower inhibitor concentration were found with SPORL-pretreated agave stalk relative to dilute acid and NaOH[230] It was also found superior to the organosolv andsteam explosion pretreatments based on the evaluation oftotal sugar recovery and energy consumption [23] The mainadvantages of sulphite pretreatment are high sugar yieldseffective lignin removal and recovery of biomass componentsin less chemically transformed formsThe drawbacks includesugar degradation at severe conditions large volumes ofprocesswater used in postpretreatmentwashing and the high

costs of recovering pretreatment chemicals It has howeverbeen shown through the work of Liu and Zhu [231] that thenegative effects of soluble inhibitors and lignosulphonate onenzymatic hydrolyses could be counteracted by adding metalsalts to the pretreated contents making it possible to avoidthe costly washing process

28 Glycerol Crude glycerolmdasha byproduct in biodieselproductionmdashhas attracted interest as a substrate for fer-mentation into ethanol and other biochemicals [232] andalso as a solvent for fractionating biomass in order toimprove the economics of cellulosic ethanol as well as theupstream biodiesel production Glycerol pretreatment causesefficient delignification of biomass Guragain et al [164]investigated the best conditions in the use of crude glycerol(water glycerol = 1 1) in pretreating wheat straw and waterhyacinth and arrived at 230∘C for 4 h for wheat straw and230∘C for 1 h for water hyacinth Enzymatic hydrolysis ofpretreated wheat straw produced reducing sugar yields (mggof sample) of 423 and 487 for crude and pure glycerolrespectively compared to a low figure of 223 for diluteacid In addition hydrolysis tests on water hyacinth gaveyields of 705 719 and 714 for crude glycerol pure glyceroland dilute acid respectively Similarly Ungurean et al [186]performed glycerol pretreatment of wood (poplar acaciaoak and fir) and recorded higher cellulose conversion ratescompared to dilute acid application However combinationsof glycerol and acidIL pretreatment yielded higher sugarlevels compared to glycerol pretreatment alone

There are wide variations in the composition of crudeglycerol which usually containsmethanol ash soap catalystssalts and nonglycerol organicmatter among others in variedproportions [233] While the potential for exploring crudeglycerol application together with other methods is highthere is the need to assess the quality of crude glycerol and itseffects on sugar and ethanol yields of promising feedstocks

29 Aqueous N-Methylmorpholine-N-Oxide (NMMO)NMMO is a well-known industrial solvent used in theLyocell process for the production of fibres and has attractedinterest for use as a pretreatment solvent Cellulose dissolves(without derivatization) in NMMOH

2O system and the

hydrogen bonds in cellulose are disrupted in favour of newbonds between cellulose and solventmolecules [234] leadingto swelling and increased porosity [235] as well as reduceddegree of polymerization and crystallinity which improvesenzymatic saccharification Addition of boiled distilled waterto pretreatment slurry containing dissolved biomass causescellulose I to precipitate into cellulose II which is morereactive Regenerated solids are filtered and washed withwarmboiling water until the filtrate is clear

Like ionic liquids NMMOdissolves biomass with nolesschemical modification at lowmoderate temperatures (80ndash130∘C) Additional favourable characteristics of NMMOpretreatment include high sugar yields formation of lowdegradation products high solvent recovery and no adverseeffect on the environment Further cellulase activity is notnegatively affected by low concentrations (15ndash20 ww) of


Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu

senergykwrec09presentationsB1Ro

bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno

lcaindexhtml(accessed060213)

40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio

n[200]httpbiofuelsdu

pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)


NMMO indicating the potential of application in continuousprocesses [235]

Aqueous NMMO has already being used on a host ofbiomass as a sole pretreatment method or in combinationwith others Almost total conversion of cellulose to ethanolat ethanol yields of up to 854 and 89 for pretreatment(130∘C3 h) of oak and spruce respectively was observed[236] High saccharification yields (gt90) were observed forultrasound-assisted NMMO treatment of sugarcane bagasse[233] as well as pretreatment of birch [237] Poornejad etal [238] compared the effectiveness of NMMO and theionic liquid (Bmim-Ac) treatment on rice straw at 120∘C5 hGlucan conversion was complete with the ionic acid while96 conversion was realized with the use of NMMO UponSSF the yield of ethanolwas higherwithNMMO(933) thanBmim-Ac (797)

At the pilot scale concentrated NMMO pretreatment(85 ww 130∘C 5 h) has been investigated on spruce andbirch by Lennartsson et al [239] Forwood chips below 2mmmaximum hydrolysis yields (mgg wood) ranged from 195to 128 for spruce and 136 to 175 for birch depending onthe scale of the pilot reactor using nonisothermal SSF Atechnoeconomic analysis of NMMO pretreatment of sprucefor ethanol and biogas production was undertaken by Shafieiet al [240] who observed relatively high process energyefficiency of 79

210 Inorganic Salts Recently salts such as iron (III) chloride[241] and calcium chloride [242] have found use in thepretreatment of biomass The salt hydrolyses in water toform a strong acidic solution which causes rapid removalof hemicelluloses from biomass during pretreatment Appli-cation of the salt (026M) to olive tree residues at 1526∘Cfor 30min resulted in 100 removal of hemicellulose andsubsequent saccharification produced a yield of 366 g glu-cose100 g of glucose in the original biomass [241] CombinedCaCl2-microwave treatment was investigated on corn stover

and under optimum conditions (1621∘C 12min) glucoserecovery reached 655 which was higher than that of steam-exploded (15MPa 5min) corn stover [242]

3 Future Outlook and Conclusion

Due to its high reactivity at mild conditions chemicalpretreatment of lignocellulosic biomass forms the basicsof several proprietary cellulosic ethanol production con-figuration and technologies that have been developed byvarious research groups and companies for developmentat various levels usually with financial support fromnational governments and public bodies (eg SwedishEnergy Agency Danish Ministry of Energy US Departmentof EnergyAgriculture and Canadian Sustainable Develop-ment Technology Canada) and multinational institutionssuch as the European Union Table 2 gives profiles ofsome of the main projects undertaken or under construc-tiondevelopment underpinned by breakthrough pretreat-ment hydrolysis and fermentation technologies as well asprocess integration and optimization

The pretreatment of feedstocks to enhance biodegradabil-ity to simple sugars has been the subject of intensive researchglobally with a focus on maximizing sugar yields at highsolid loads and at the lowest economic and environmentalcosts This paper has reviewed widely known and emerg-ing chemical pretreatment methods with regard to processdescription advantages drawbacks and recent innovationsemployed to offset inherent challenges Though cellulosicethanol is close to commercialization there are still tech-nical economic and environmental challenges associatedwith biomass pretreatment hydrolysis and fermentation Nosolvent has been found to work best for all biomass andsuch optimized methods and process conditions for variousmaterials need to be investigated and developed further

Some major challenges of the chemical pretreatmentinclude the requirement of extensive size reduction handlingbiomass at high solids concentration corrosion solventcosts and recovery environmental pollution from solventsbyproducts and waste from reactions Nonetheless theaforementioned challenges are being dealt with via severalinterventions notably the application of novel solvents andthe combination of different chemical methods with physico-chemical and biological pretreatments to achieve highersugar yields milder process conditions lower use of costlysolvents low enzyme loads recovery and use of biomasscomponents in pristine forms and improvements in environ-mental sustainability

Acknowledgment

The authors are grateful to DANIDA through the devel-opment research project (DFC journal no 10-018RISOslash)titledmdashBiofuels production from lignocellulosic materials(2GBIONRG)

References

[1] J S Lim Z Abdul Manan S R Wan Alwi and H Hashim ldquoAreviewonutilisation of biomass from rice industry as a source ofrenewable energyrdquo Renewable and Sustainable Energy Reviewsvol 16 no 5 pp 3084ndash3094 2012

[2] Y Z Pang Y P Liu X J Li K S Wang and H R YuanldquoImproving biodegradability and biogas production of cornstover through sodium hydroxide solid state pretreatmentrdquoEnergy and Fuels vol 22 no 4 pp 2761ndash2766 2008

[3] J Gabhane S PM PrinceWilliam AN Vaidya KMahapatraand T Chakrabarti ldquoInfluence of heating source on the efficacyof lignocellulosic pretreatmentmdasha cellulosic ethanol perspec-tiverdquo Biomass and Bioenergy vol 35 no 1 pp 96ndash102 2011

[4] Y Kim R Hendrickson N S Mosier et al ldquoEnzyme hydrol-ysis and ethanol fermentation of liquid hot water and AFEXpretreated distillersrsquo grains at high-solids loadingsrdquo BioresourceTechnology vol 99 no 12 pp 5206ndash5215 2008

[5] J-S Lee B Parameswaran J-P Lee and S-C Park ldquoRecentdevelopments of key technologies on cellulosic ethanol produc-tionrdquo Journal of Scientific and Industrial Research vol 67 no 11pp 865ndash873 2008

[6] Y Li R Ruan P L Chen et al ldquoEnzymatic hydrolysis ofcorn stover pretreated by combined dilute alkaline treatment


and homogenizationrdquo Transactions of the American Society ofAgricultural Engineers vol 47 no 3 pp 821ndash825 2004

[7] P Harmsen W Huijgen L Bermudez and R Bakker ldquoLitera-ture review of physical and chemical pretreatment processes forlignocellulosic biomassrdquo Tech Rep 1184 Biosynergy Wagenin-gen UR Food amp Biobased Research 2010

[8] J-W Lee and T W Jeffries ldquoEfficiencies of acid catalysts in thehydrolysis of lignocellulosic biomass over a range of combinedseverity factorsrdquo Bioresource Technology vol 102 no 10 pp5884ndash5890 2011

[9] J S VanDyk and B I Pletschke ldquoA review of lignocellulose bio-conversion using enzymatic hydrolysis and synergistic cooper-ation between enzymes-Factors affecting enzymes conversionand synergyrdquo Biotechnology Advances vol 30 no 6 pp 1458ndash1480 2012

[10] J D McMillan ldquoBioethanol production status and prospectsrdquoRenewable Energy vol 10 no 2-3 pp 295ndash302 1997

[11] D M Lavenson E J Tozzi N Karuna T Jeoh R L Powelland M J McCarthy ldquoThe effect of mixing on the liquefactionand saccharification of cellulosic fibersrdquoBioresource Technologyvol 111 pp 240ndash247 2012

[12] G Radeva I Valchev S Petrin E Valcheva and P TsekovaldquoKinetic model of enzymatic hydrolysis of steam-explodedwheat strawrdquo Carbohydrate Polymers vol 87 no 2 pp 1280ndash1285 2012

[13] Y Sun and J Cheng ldquoHydrolysis of lignocellulosic materials forethanol production a reviewrdquo Bioresource Technology vol 83no 1 pp 1ndash11 2002

[14] B Yang and C E Wyman ldquoPretreatment the key to unlockinglow-cost cellulosic ethanolrdquo Biofuels Bioproducts and Biorefin-ing vol 2 no 1 pp 26ndash40 2008

[15] R C Kuhad R Gupta Y P Khasa A Singh andY-H P ZhangldquoBioethanol production frompentose sugars current status andfuture prospectsrdquo Renewable and Sustainable Energy Reviewsvol 15 no 9 pp 4950ndash4962 2011

[16] R Choudhary A L Umagiliyage Y Liang T Siddaramu JHaddock and G Markevicius ldquoMicrowave pretreatment forenzymatic saccharification of sweet sorghum bagasserdquo Biomassand Bioenergy vol 39 pp 218ndash226 2012

[17] M Galbe and G Zacchi ldquoPretreatment the key to efficientutilization of lignocellulosic materialsrdquo Biomass Bioenergy vol46 pp 70ndash78 2012

[18] N Sarkar S K Ghosh S Bannerjee and K Aikat ldquoBioethanolproduction from agricultural wastes an overviewrdquo RenewableEnergy vol 37 no 1 pp 19ndash27 2012

[19] C E Wyman B E Dale R T Elander M Holtzapple M RLadisch and Y Y Lee ldquoCoordinated development of leadingbiomass pretreatment technologiesrdquo Bioresource Technologyvol 96 no 18 pp 1959ndash1966 2005

[20] T Eggeman and R T Elander ldquoProcess and economic analysisof pretreatment technologiesrdquo Bioresource Technology vol 96no 18 pp 2019ndash2025 2005

[21] L Tao A Aden R T Elander et al ldquoProcess and technoe-conomic analysis of leading pretreatment technologies for lig-nocellulosic ethanol production using switchgrassrdquo BioresourceTechnology vol 102 no 24 pp 11105ndash11114 2011

[22] C E Wyman B E Dale R T Elander et al ldquoComparativesugar recovery and fermentation data following pretreatment ofpoplar wood by leading technologiesrdquo Biotechnology Progressvol 25 no 2 pp 333ndash339 2009

[23] J Y Zhu and X J Pan ldquoWoody biomass pretreatment for cellu-losic ethanol production technology and energy consumptionevaluationrdquo Bioresource Technology vol 101 no 13 pp 4992ndash5002 2010

[24] S Sanchez-Segado L J Lozano A P de los Rıos F JHernandez-Fernandez C Godinez and D Juan ldquoProcessdesign and economic analysis of a hypothetical bioethanolproduction plant using carob pod as feedstockrdquo BioresourceTechnology vol 104 pp 324ndash328 2012

[25] J Littlewood R J Murphy and L Wang ldquoImportance ofpolicy support and feedstock prices on economic feasibility ofbioethanol production from wheatstraw in the UKrdquo Renewableamp Sustainable Energy Reviews vol 17 pp 291ndash300 2013

[26] N Mosier C Wyman B Dale et al ldquoFeatures of promisingtechnologies for pretreatment of lignocellulosic biomassrdquoBiore-source Technology vol 96 no 6 pp 673ndash686 2005

[27] D Chiaramonti A M Rizzo M Prussi et al ldquo2nd generationlignocellulosic bioethanol is torrefaction a possible approachto biomass pretreatmentrdquo Biomass Conversion and Biorefineryvol 1 pp 9ndash15 2011

[28] T Rogalinski T Ingram and G Brunner ldquoHydrolysis oflignocellulosic biomass in water under elevated temperaturesand pressuresrdquo Journal of Supercritical Fluids vol 47 no 1 pp54ndash63 2008

[29] G Hu J A Heitmann and O J Rojas ldquoFeedstock pretreatmentstrategies for producing ethanol from wood bark and forestresiduesrdquo BioResources vol 3 no 1 pp 270ndash294 2008

[30] V B Agbor N Cicek R Sparling A Berlin and D BLevin ldquoBiomass pretreatment fundamentals toward applica-tionrdquo Biotechnology Advances vol 29 no 6 pp 675ndash685 2011

[31] I F Cullis and S D Mansfield ldquoOptimized delignification ofwood-derived lignocellulosics for improved enzymatic hydrol-ysisrdquo Biotechnology and Bioengineering vol 106 no 6 pp 884ndash893 2010

[32] S Thongkheaw and B Pitiyont Enzymatic Hydrolysis of Acid-Pretreated Sugarcane Shoot vol 60 World Academy of ScienceEngineering and Technology 2011

[33] M Pedersen K S Johansen andA SMeyer ldquoLow temperaturelignocellulose pretreatment effects and interactions of pretreat-ment pHare critical formaximizing enzymaticmonosaccharideyields from wheat strawrdquo Biotechnology for Biofuels vol 4article 11 2011

[34] J Y Zhu X Pan and R S Zalesny Jr ldquoPretreatment of woodybiomass for biofuel production energy efficiency technologiesand recalcitrancerdquo Applied Microbiology and Biotechnology vol87 no 3 pp 847ndash857 2010

[35] C M Roche C J Dibble and J J Stickel ldquoLaboratory-scale method for enzymatic saccharification of lignocellulosicbiomass at high-solids loadingsrdquo Biotechnology for Biofuels vol2 no 1 article 28 pp 1ndash11 2009

[36] B Bals C Rogers M Jin V Balan and B Dale ldquoEvaluation ofammonia fibre expansion (AFEX) pretreatment for enzymatichydrolysis of switchgrass harvested in different seasons andlocationsrdquo Biotechnology for Biofuels vol 3 article 1 2010

[37] B S Dien H-J G Jung K P Vogel et al ldquoChemical compo-sition and response to dilute-acid pretreatment and enzymaticsaccharification of alfalfa reed canarygrass and switchgrassrdquoBiomass and Bioenergy vol 30 no 10 pp 880ndash891 2006

[38] C Li B Knierim C Manisseri et al ldquoComparison of diluteacid and ionic liquid pretreatment of switchgrass biomassrecalcitrance delignification and enzymatic saccharificationrdquoBioresource Technology vol 101 no 13 pp 4900ndash4906 2010


[39] Z-H Liu L QinM-J Jin et al ldquoEvaluation of storagemethodsfor the conversion of corn stover biomass to sugars based onsteam explosion pretreatmentrdquo Bioresource Technology vol 132pp 5ndash15 2013

[40] O Bobleter ldquoHydrothermal degradation of polymers derivedfrom plantsrdquo Progress in Polymer Science vol 19 no 5 pp 797ndash841 1994

[41] A Demirbas ldquoProducts from lignocellulosic materials viadegradation processesrdquo Energy Sources A vol 30 no 1 pp 27ndash37 2008

[42] M Tutt T Kikas and J Olt ldquoInfluence of different pretreatmentmethods on bioethanol production from wheat strawrdquo Agron-omy Research Biosystem Engineering vol 1 pp 269ndash276 2012

[43] R Samuel Y Pu M Foston and A J Ragauskas ldquoSolid-stateNMR characterization of switchgrass cellulose after dilute acidpretreatmentrdquo Biofuels vol 1 no 1 pp 85ndash90 2010

[44] M Foston and A J Ragauskas ldquoChanges in lignocellulosicsupramolecular and ultrastructure during dilute acid pretreat-ment of Populus and switchgrassrdquo Biomass and Bioenergy vol34 no 12 pp 1885ndash1895 2010

[45] X Chen J Shekiro M A Franden et al ldquoThe impactsof deacetylation prior to dilute acid pretreatment on thebioethanol processrdquo Biotechnology for Biofuels vol 5 article 82012

[46] J Tang K Chen J Xu J Li and C Zhao ldquoEffects of diluteacid hydrolysis on composition and structure of cellulose ineulaliopsis binatardquo BioResources vol 6 no 2 pp 1069ndash10782011

[47] R G Candido G G Godoy and A R Goncalves Study ofSugarcane Bagasse Pretreatment With Sulfuric Acid As a Stepof Cellulose Obtaining vol 61 World Academy of ScienceEngineering and Technology 2012

[48] S V Pingali V S Urban W T Heller et al ldquoBreakdownof cell wall nanostructure in dilute acid pretreated biomassrdquoBiomacromolecules vol 11 no 9 pp 2329ndash2335 2010

[49] H L Chum D K Johnson S K Black and R P OverendldquoPretreatment-catalyst effects and the combined severityparameterrdquo Applied Biochemistry and Biotechnology vol 24-25pp 1ndash14 1990

[50] V Menon and M Rao ldquoTrends in bioconversion of ligno-cellulose biofuels platform chemicals amp biorefinery conceptrdquoProgress in Energy and Combustion Science vol 38 no 4 pp522ndash550 2012

[51] M Galbe and G Zacchi ldquoA review of the production of ethanolfrom softwoodrdquo Applied Microbiology and Biotechnology vol59 no 6 pp 618ndash628 2002

[52] D Zhang Y L Ong Z Li and J CWu ldquoOptimization of diluteacid-catalyzed hydrolysis of oil palm empty fruit bunch for highyield production of xyloserdquo Chemical Engineering Journal vol181-182 pp 636ndash642 2012

[53] F K Kazi J Fortman R Anex et al ldquoTechno-Economicanalysis of biochemical scenarios for production of cellulosicethanolrdquo Tech Rep NRELTP-6A2-46588 NREL 2010

[54] F Talebnia D Karakashev and I Angelidaki ldquoProduction ofbioethanol from wheat straw an overview on pretreatmenthydrolysis and fermentationrdquo Bioresource Technology vol 101no 13 pp 4744ndash4753 2010

[55] A Li B Antizar-Ladislao andM Khraisheh ldquoBioconversion ofmunicipal solid waste to glucose for bio-ethanol productionrdquoBioprocess and Biosystems Engineering vol 30 no 3 pp 189ndash196 2007

[56] M Brodeur-Campbell J Klinger and D Shonnard ldquoFeedstockmixture effects on sugar monomer recovery following diluteacid pretreatment and enzymatic hydrolysisrdquo Bioresource Tech-nology vol 116 pp 320ndash326 2012

[57] M Tutt T Kikas and J Olt Comparison of Different Pretreat-ment Methods on Degradation of Rye Straw Engineering forRural Development Jelgava Latvia 2012

[58] P Lenihan A Orozco E OrsquoNeill M N M Ahmad DW Rooney and G M Walker ldquoDilute acid hydrolysis oflignocellulosic biomassrdquoChemical Engineering Journal vol 156no 2 pp 395ndash403 2010

[59] B Hong G Xue L Weng and X Guo ldquoPretreatment of mosobamboo with dilute phosphoric acidrdquo BioResources vol 7 no 4pp 4902ndash4913 2012

[60] S Satimanont A Luengnaruemitchai and S WongkasemjitldquoEffect of temperature and time on dilute acid pretreatmentof corn cobsrdquo International Journal of Chemical and BiologicalEngineering vol 6 2012

[61] A Avci B C Saha B S Dien et al ldquoResponse surface optimiza-tion of corn stover pretreatment using dilute phosphoric acidfor enzymatic hydrolysis and ethanol productionrdquo BioresourceTechnology vol 130 pp 603ndash612 2013

[62] E Heredia-Olea E Perez-Carrillo and S O Serna-SaldıvarldquoEffects of different acid hydrolyses on the conversion of sweetsorghum bagasse into C5 and C6 sugars and yeast inhibitorsusing response surface methodologyrdquo Bioresource Technologyvol 119 pp 216ndash223 2012

[63] M F Digman K J Shinners R E Muck and B S Dien ldquoPilot-scale on-farm pretreatment of perennial grasses with diluteacid and alkali for fuel ethanol productionrdquo Transactions of theASABE vol 53 no 3 pp 1007ndash1014 2010

[64] J-W Lee C J Houtman H-Y Kim I-G Choi and T WJeffries ldquoScale-up study of oxalic acid pretreatment of agricul-tural lignocellulosic biomass for the production of bioethanolrdquoBioresource Technology vol 102 no 16 pp 7451ndash7456 2011

[65] J-W Lee R C L B Rodrigues H J Kim I-G Choi andT W Jeffries ldquoThe roles of xylan and lignin in oxalic acidpretreated corncob during separate enzymatic hydrolysis andethanol fermentationrdquo Bioresource Technology vol 101 no 12pp 4379ndash4385 2010

[66] X Li Z Cai E Horn and J E Winandy ldquoEffect of oxalic acidpretreatment of wood chips onmanufacturingmedium-densityfiberboardrdquo Holzforschung vol 65 no 5 pp 737ndash741 2011

[67] X Li Z Cai E Horn and J E Winandy ldquoOxalic acidpretreatment of rice straw particles and loblolly pine chipsrelease of hemicellulosic carbohydratesrdquo Tappi Journal vol 10no 5 pp 41ndash45 2011

[68] D Scordia S L Cosentino J-W Lee and T W Jeffries ldquoDiluteoxalic acid pretreatment for biorefining giant reed (Arundodonax L)rdquo Biomass and Bioenergy vol 35 no 7 pp 3018ndash30242011

[69] A A Modenbach and S E Nokes ldquoThe use of high-solidsloadings in biomass pretreatment-a reviewrdquo Biotechnology andBioengineering vol 109 no 6 pp 1430ndash1442 2012

[70] G Y S Mtui ldquoOxalic acid pretreatment fungal enzymaticsaccharification and fermentation of maize residues to ethanolrdquoAfrican Journal of Biotechnology vol 11 no 4 pp 843ndash851 2012

[71] T Zhang R Kumar andC EWyman ldquoSugar yields fromdiluteoxalic acid pretreatment ofmaple wood compared to those withother dilute acids and hot waterrdquo Carbohydrate Polymers vol92 pp 334ndash344 2013


[72] M Sharma and A Kumar ldquoXylanases an overviewrdquo BritishBiotechnology Journal vol 3 no 1 pp 1ndash28 2013

[73] D Kumar and G S Murthy ldquoImpact of pretreatment anddownstream processing technologies on economics and energyin cellulosic ethanol productionrdquo Biotechnology for Biofuels vol4 article 27 2011

[74] C Conde-Mejıa A Jimenez-Gutierreza andM El-Halwagi ldquoAcomparison of pretreatment methods for bioethanol produc-tion from lignocellulosic materialsrdquo Safety and EnvironmentalProtection vol 90 no 3 pp 189ndash202 2012

[75] C Cara I Romero J M Oliva F Saez and E Castro ldquoLiquidhot water pretreatment of olive tree pruning residuesrdquo AppliedBiochemistry and Biotechnology vol 136ndash140 no 1ndash12 pp 379ndash394 2007

[76] Z AnwarM Gulfraz M J Asad et al ldquoBioethanol productionsfrom rice polish by optimization of dilute acid pretreatment andenzymatic hydrolysisrdquo African Journal of Biotechnology vol 11no 4 pp 992ndash998 2012

[77] T S Jeong C H Choi J Y Lee and K K Oh ldquoBehaviorsof glucose decomposition during acid-catalyzed hydrothermalhydrolysis of pretreated Gelidium amansiirdquo Bioresource Tech-nology vol 116 pp 435ndash440 2012

[78] R Jutakanoke N Leepipatpiboon V Tolieng V Kitpreecha-vanich T Srinorakutara and A Akaracharanya ldquoSugarcaneleaves pretreatment and ethanol fermentation by Saccha-romyces cerevisiaerdquo Biomass and Bioenergy vol 39 pp 283ndash289 2012

[79] Y-B Yi J-W Lee Y-H Choi S-M Park and C-H ChungldquoSimple process for production of hydroxymethylfurfural fromraw biomasses of girasol and potato tubersrdquo Biomass andBioenergy vol 39 pp 484ndash488 2012

[80] Z Anwar M Gulfraz M Imran et al ldquoOptimization of diluteacid pretreatment using response surface methodology forbioethanol production from cellulosic biomass of rice polishrdquoPakistan Journal of Botany vol 44 no 1 pp 169ndash176 2012

[81] D L Grzenia D J Schell and S R Wickramasinghe ldquoMem-brane extraction for detoxification of biomass hydrolysatesrdquoBioresource Technology vol 111 pp 248ndash254 2012

[82] AM Shupe and S Liu ldquoEthanol fermentation from hydrolysedhot-water wood extracts by pentose fermenting yeastsrdquoBiomassand Bioenergy vol 39 pp 31ndash38 2012

[83] L Viikari J Vehmaanpera and A Koivula ldquoLignocellulosicethanol from science to industryrdquo Biomass Bioenergy vol 46pp 13ndash24 2012

[84] Y H Jung I J Kim H K Kim and K H Kim ldquoDiluteacid pretreatment of lignocellulose for whole slurry ethanolfermentationrdquo Bioresource Technology vol 132 pp 109ndash1142013

[85] R Koppram E Albers and L Olsson ldquoEvolutionary engi-neering strategies to enhance tolerance of xylose utilizingrecombinant yeast to inhibitors derived from spruce biomassrdquoBiotechnology for Biofuels vol 5 article 32 2012

[86] X Ju M Engelhard and X Zhang ldquoAn advanced understand-ing of the specific effects of xylan and surface lignin contentson enzymatic hydrolysis of lignocellulosic biomassrdquo BioresourceTechnology vol 132 pp 137ndash145 2013

[87] L Favaro M Basaglia and S Casella ldquoProcessing wheat braninto ethanol using mild treatments and highly fermentativeyeastsrdquo Biomass Bioenergy vol 46 pp 605ndash617 2012

[88] X Gao R Kumar J D DeMartini H Li and C EWyman ldquoApplication of high throughput pretreatment and

co-hydrolysis system to thermochemical pretreatmentmdashpart 1dilute acidrdquo Biotechnology and Bioengineering vol 110 no 3 pp754ndash762 2013

[89] Z S Liu X L Wu K Kida and Y Q Tang ldquoCorn stoversaccharification with concentrated sulfuric acid effects ofsaccharification conditions on sugar recovery and by-productgenerationrdquo Bioresource Technology vol 119 pp 224ndash233 2012

[90] M H M Zainudin N A Rahman S Abd-Aziz et al ldquoUti-lization of glucose recovered by phase separation system fromacid-hydrolysed oil palm empty fruit bunch for bioethanolproductionrdquo Pertanika Journal of Tropical Agricultural Sciencevol 35 no 1 pp 117ndash126 2012

[91] Y-H P Zhang S-Y Ding J R Mielenz et al ldquoFractionat-ing recalcitrant lignocellulose at modest reaction conditionsrdquoBiotechnology and Bioengineering vol 97 no 2 pp 214ndash2232007

[92] J W van Groenestijn J H O Hazewinkel and R R BakkerPre-Treatment of Ligno-Cellulose With Biological Acid Recycling(The Biosulfurol Process) Netherlands Organisation for AppliedScientific Research (TNO) Zeist The Netherlands 2007

[93] Y H P Zhang Z Zhu R Rollin and N SathitsuksanohldquoAdvances in cellulose solvent- and organic solvent-based ligno-cellulose fractionation (COSLIF) in cellulose solventsrdquo inCellu-lose Solvents For Analysis Shaping and Chemical ModificationT Liebert T Heinze and K Edgar Eds vol 1033 of AmericanChemical Society Symposium Series pp 365ndash379 2010

[94] J Zhang B Zhang J Zhang L Lin S Liu and P OuyangldquoEffect of phosphoric acid pretreatment on enzymatic hydrol-ysis of microcrystalline celluloserdquo Biotechnology Advances vol28 no 5 pp 613ndash619 2010

[95] N Sathitsuksanoh Z Zhu and Y H P Zhang ldquoCellulosesolvent- and organic solvent-based lignocellulose fractionationenabled efficient sugar release from a variety of lignocellulosicfeedstocksrdquo Bioresource Technology vol 117 pp 228ndash233 2012

[96] N Sathitsuksanoh Z Zhu T-J Ho M-D Bai and Y-H PZhang ldquoBamboo saccharification through cellulose solvent-based biomass pretreatment followed by enzymatic hydrolysisat ultra-low cellulase loadingsrdquo Bioresource Technology vol 101no 13 pp 4926ndash4929 2010

[97] N Sathitsuksanoh Z Zhu and Y H P Zhang ldquoCellulosesolvent-based pretreatment for corn stover and avicel concen-trated phosphoric acid versus ionic liquid [BMIM]ClrdquoCellulosevol 19 no 4 pp 1161ndash1172 2012

[98] J Xu X Zhang and J J Cheng ldquoPretreatment of corn stoverfor sugar production with switchgrass-derived black liquorrdquoBioresource Technology vol 111 pp 255ndash260 2012

[99] J E Lindberg I E Ternrud andOTheander ldquoDegradation rateand chemical composition of different types of Alkali-treatedstraws during rumen digestionrdquo Journal of the Science of Foodand Agriculture vol 35 pp 500ndash506 1984

[100] X Zhao L Zhang and D Liu ldquoPretreatment of Siam weedstem by several chemical methods for increasing the enzymaticdigestibilityrdquo Biotechnology Journal vol 5 no 5 pp 493ndash5042010

[101] H Y Yoo S B Kim H S Choi K Kim C Park and SW Kim ldquoOptimization of sodium hydroxide pretreatment ofcanola agricultural residues for fermentable sugar productionusing statistical methodrdquo in Proceedings of the InternationalConference on Future Environment and Energy (IPCBEE rsquo12)vol 28 2012

[102] P Boonsawang Y Subkaree and T Srinorakutara ldquoEthanolproduction from palm pressed fiber by prehydrolysis prior to


simultaneous saccharification and fermentation (SSF)rdquoBiomassand Bioenergy vol 40 pp 127ndash132 2012

[103] Y-S Cheng Y Zheng C W Yu T M Dooley B M Jenkinsand J S Vandergheynst ldquoEvaluation of high solids alkalinepretreatment of rice strawrdquo Applied Biochemistry and Biotech-nology vol 162 no 6 pp 1768ndash1784 2010

[104] A T W M Hendriks and G Zeeman ldquoPretreatments toenhance the digestibility of lignocellulosic biomassrdquoBioresourceTechnology vol 100 no 1 pp 10ndash18 2009

[105] F Peng J Bian J-L Ren P Peng F Xu and R-C SunldquoFractionation and characterization of alkali-extracted hemi-celluloses from peashrubrdquo Biomass and Bioenergy vol 39 pp20ndash30 2012

[106] L Yang J Cao Y Jin et al ldquoEffects of sodium carbonatepretreatment on the chemical compositions and enzymaticsaccharification of rice strawrdquo Bioresource Technology vol 124pp 283ndash291 2012

[107] L Yang J Cao J Mao and Y Jin ldquoSodium carbonate-sodiumsulfite pretreatment for improving the enzymatic hydrolysis ofrice strawrdquo Industrial Crops and Products vol 43 pp 711ndash7172013

[108] Y Zhao Y Wang J Y Zhu A Ragauskas and Y DengldquoEnhanced enzymatic hydrolysis of spruce by alkaline pretreat-ment at low temperaturerdquo Biotechnology and Bioengineeringvol 99 no 6 pp 1320ndash1328 2008

[109] R A Silverstein Y Chen R R Sharma-Shivappa M DBoyette and J Osborne ldquoA comparison of chemical pretreat-ment methods for improving saccharification of cotton stalksrdquoBioresource Technology vol 98 no 16 pp 3000ndash3011 2007

[110] K Mirahmadi M M Kabir A Jeihanipour K Karimi and MJ Taherzadeh ldquoAlkaline pretreatment of spruce and birch toimprove bioethanol and biogas productionrdquo BioResources vol5 no 2 pp 928ndash938 2010

[111] X Zhao F Peng K Cheng and D Liu ldquoEnhancement of theenzymatic digestibility of sugarcane bagasse by alkali-peraceticacid pretreatmentrdquo Enzyme and Microbial Technology vol 44no 1 pp 17ndash23 2009

[112] M Ioelovich and E Morag ldquoStudy of enzymatic hydrolysis ofmild pretreated lignocellulosic biomassesrdquo BioResources vol 7no 1 pp 1040ndash1052 2012

[113] S Ji and I Lee ldquoImpact of cationic polyelectrolyte on the nanos-hear hybrid alkaline pretreatment of corn stover morphologyand saccharification studyrdquo Bioresource Technology vol 133 pp45ndash50 2013

[114] Y Xing L X Bu K Wang and J X Jiang ldquoPretreatment offurfural residues with alkaline peroxide to improve cellulosehydrolysis Characterization of isolated ligninrdquo Cellulose Chem-istry and Technology vol 46 no 3-4 pp 249ndash260 2012

[115] W Cao C Sun R Liu R Yin and X Wu ldquoComparisonof the effects of five pretreatment methods on enhancing theenzymatic digestibility and ethanol production from sweetsorghum bagasserdquo Bioresource Technology vol 111 pp 215ndash2212012

[116] K Minu K K Jiby and V V N Kishore ldquoIsolation andpurification of lignin and silica from the black liquor generatedduring the production of bioethanol from rice strawrdquo Biomassand Bioenergy vol 39 pp 210ndash217 2012

[117] G Banerjee S Car J S Scott-Craig D B Hodge and J DWalton ldquoAlkaline peroxide pretreatment of corn stover effectsof biomass peroxide and enzyme loading and composition onyields of glucose and xyloserdquo Biotechnology for Biofuels vol 4article 16 2011

[118] G Banerjee S Car J S Scott-Craig M S Borrusch and J DWalton ldquoRapid optimization of enzyme mixtures for decon-struction of diverse pretreatmentbiomass feedstock combina-tionsrdquo Biotechnology for Biofuels vol 3 article 22 2010

[119] M Falls and M T Holtzapple ldquoOxidative lime pretreatmentof alamo switchgrassrdquo Applied Biochemistry and Biotechnologyvol 165 no 2 pp 506ndash522 2011

[120] R Kumar G Mago V Balan and C E Wyman ldquoPhysicaland chemical characterizations of corn stover and poplar solidsresulting from leading pretreatment technologiesrdquo BioresourceTechnology vol 100 no 17 pp 3948ndash3962 2009

[121] B C Saha and M A Cotta ldquoLime pretreatment enzymaticsaccharification and fermentation of rice hulls to ethanolrdquoBiomass and Bioenergy vol 32 no 10 pp 971ndash977 2008

[122] R Kumar and C E Wyman ldquoCellulase adsorption and rela-tionship to features of corn stover solids produced by leadingpretreatmentsrdquo Biotechnology and Bioengineering vol 103 no2 pp 252ndash267 2009

[123] L L G Fuentes S C Rabelo R M Filho and A C CostaldquoKinetics of lime pretreatment of sugarcane bagasse to enhanceenzymatic hydrolysisrdquo Applied Biochemistry and Biotechnologyvol 163 no 5 pp 612ndash625 2011

[124] W E Kaar and M T Holtzapple ldquoUsing lime pretreatment tofacilitate the enzymic hydrolysis of corn stoverrdquo Biomass andBioenergy vol 18 no 3 pp 189ndash199 2000

[125] R J Garlock V Balan B E Dale et al ldquoComparative materialbalances around pretreatment technologies for the conversionof switchgrass to soluble sugarsrdquo Bioresource Technology vol102 no 24 pp 11063ndash11071 2011

[126] S C Rabelo R M Filho and A C Costa ldquoA comparisonbetween lime and alkaline hydrogen peroxide pretreatments ofsugarcane bagasse for ethanol productionrdquo Applied Biochem-istry and Biotechnology vol 148 no 1ndash3 pp 45ndash58 2008

[127] R Prado X Erdocia L Serrano and J Labidi ldquoLignin purifica-tion with green solventsrdquo Cellulose Chemistry and Technologyvol 46 no 3-4 pp 221ndash225 2012

[128] R T Elander B E Dale M Holtzapple et al ldquoSummary offindings from the Biomass Refining Consortium for AppliedFundamentals and Innovation (CAFI) corn stover pretreat-mentrdquo Cellulose vol 16 no 4 pp 649ndash659 2009

[129] B D Schutt and M A Abraham ldquoEvaluation of a monolithreactor for the catalytic wet oxidation of celluloserdquo ChemicalEngineering Journal vol 103 no 1ndash3 pp 77ndash88 2004

[130] S Rovio A Kallioinen T Tamminen M Hakola M Leskelaand M Siika-ahoa ldquoCatalysed alkaline oxidation as a woodfractionation techniquerdquo BioResources vol 7 no 1 pp 756ndash7762012

[131] H Palonen A B Thomsen M Tenkanen A S Schmidtand L Viikari ldquoEvaluation of wet oxidation pretreatment forenzymatic hydrolysis of softwoodrdquo Applied Biochemistry andBiotechnology A vol 117 no 1 pp 1ndash17 2004

[132] C Martın Y Gonzalez T Fernandez and A B ThomsenldquoInvestigation of cellulose convertibility and ethanolic fer-mentation of sugarcane bagasse pretreated by wet oxidationand steam explosionrdquo Journal of Chemical Technology andBiotechnology vol 81 no 10 pp 1669ndash1677 2006

[133] A B Thomsen and S Schmidt Further Development ofChemical and Biological Processes for Production of BioethanolOptimisation of Pre-Treatment Processes and Characterisation ofProducts Risoslash-R-1110(EN) Risoslash National Laboratory RoskildeDenmark 1999


[134] H B Klinke L Olsson A B Thomsen and B K AhringldquoPotential inhibitors from wet oxidation of wheat straw andtheir effect on ethanol production of Saccharomyces cerevisiaewet oxidation and fermentation by yeastrdquo Biotechnology andBioengineering vol 81 no 6 pp 738ndash747 2003

[135] E Arvaniti A B Bjerre and J E Schmidt ldquoWet oxidationpretreatment of rape straw for ethanol productionrdquoBiomass andBioenergy vol 39 pp 94ndash105 2012

[136] S Banerjee R Sen R A Pandey et al ldquoEvaluation of wet airoxidation as a pretreatment strategy for bioethanol productionfrom rice husk and process optimizationrdquo Biomass and Bioen-ergy vol 33 no 12 pp 1680ndash1686 2009

[137] A Petersson M H Thomsen H Hauggaard-Nielsen and A-BThomsen ldquoPotential bioethanol and biogas production usinglignocellulosic biomass from winter rye oilseed rape and fababeanrdquoBiomass andBioenergy vol 31 no 11-12 pp 812ndash819 2007

[138] A B Bjerre and A S Schmidt Development of Chemical andBiological Processes for Production of Bioethanol Optimizationof the Wet Oxidation Process and Characterizaiton of ProductsRisoslash-R-967 (EN) Risoslash National Laboratory Roskilde Den-mark 1997

[139] A O Ayeni S Banerjee J A Omoleye et al ldquoOptimization ofpretreatment conditions using full factorial design and enzy-matic convertibility of shea tree sawdustrdquo Biomass Bioenergyvol 48 pp 130ndash138 2013

[140] A O Ayeni F K Hymore S N Mudliar et al ldquoHydrogenperoxide and lime based oxidative pretreatment of wood wasteto enhance enzymatic hydrolysis for a biorefinery processparameters optimization using response surface methodologyrdquoFuel vol 106 pp 187ndash194 2013

[141] MG Alriols A TejadoM Blanco IMondragon and J LabidildquoAgricultural palm oil tree residues as rawmaterial for celluloselignin andhemicelluloses production by ethylene glycol pulpingprocessrdquo Chemical Engineering Journal vol 148 no 1 pp 106ndash114 2009

[142] H L Chum L J Douglas D A Feinberg and H A SchroederEvaluation of Pretreatments of Biomass for Enzymatic Hydrolysisof Cellulose US Department of Energy Contract No DE-AC02-83CHt0093 1985

[143] B W Koo B C Min K S Gwak et al ldquoStructural changesin lignin during organosolv pretreatment of Liriodendrontulipifera and the effect on enzymatic hydrolysisrdquo BiomassBioenergy vol 42 pp 24ndash32 2012

[144] N Park H-Y Kim B-W Koo H Yeo and I-G ChoildquoOrganosolv pretreatment with various catalysts for enhancingenzymatic hydrolysis of pitch pine (Pinus rigida)rdquo BioresourceTechnology vol 101 no 18 pp 7046ndash7053 2010

[145] D Haverty K Dussan A V Piterina J J Leahy and M H BHayes ldquoAutothermal single-stage performic acid pretreatmentof Miscanthus x giganteus for the rapid fractionation of itsbiomass components into a ligninhemicellulose-rich liquorand a cellulase-digestible pulprdquo Bioresource Technology vol 109pp 173ndash177 2012

[146] L Mesa E Gonzalez C Cara M Gonzalez E Castro and SI Mussatto ldquoThe effect of organosolv pretreatment variables onenzymatic hydrolysis of sugarcane bagasserdquo Chemical Engineer-ing Journal vol 168 no 3 pp 1157ndash1162 2011

[147] X Zhao and D Liu ldquoFractionating pretreatment of sugarcanebagasse by aqueous formic acid with direct recycle of spentliquor to increase cellulose digestibility-the Formiline processrdquoBioresource Technology vol 117 pp 25ndash32 2012

[148] J J Villaverde P Ligero and A de Vega ldquoMiscanthus xgiganteus as a source of biobased products through organosolvfractionation a mini reviewrdquoTheOpen Agriculture Journal vol4 pp 102ndash110 2010

[149] L Kupiainen J Ahola and J Tanskanen ldquoHydrolysis of organo-solv wheat pulp in formic acid at high temperature for glucoseproductionrdquo Bioresource Technology vol 116 pp 29ndash35 2012

[150] Y Kim A Yu M Han G-W Choi and B Chung ldquoEnhancedenzymatic saccharification of barley straw pretreated by ethano-solv technologyrdquo Applied Biochemistry and Biotechnology vol163 no 1 pp 143ndash152 2011

[151] W J J Huijgen R R Van der Laan and J H Reith ldquoMordifiedorganosolv as a fractionation process of lignocellulosic biomassfor coproduction of fuels and chemicalsrdquo in Proceedings of the16th Europeran Biomass Conference and Exhibition ValenciaSpain 2008

[152] E K Pye and J H Lora ldquoThe AlcellTM process a provenalternative to kraft pulpingrdquo Tappi Joumd vol 113 1991

[153] C Arato E K Pye and G Gjennestad ldquoThe lignol approachto biorefining of woody biomass to produce ethanol andchemicalsrdquo Applied Biochemistry and Biotechnology A vol 123no 1ndash3 pp 871ndash882 2005

[154] X Pan C Arato N Gilkes et al ldquoBiorefining of softwoodsusing ethanol organosolv pulping preliminary evaluation ofprocess streams for manufacture of fuel-grade ethanol and co-productsrdquo Biotechnology and Bioengineering vol 90 no 4 pp473ndash481 2005

[155] X PanNGilkes J Kadla et al ldquoBioconversion of hybrid poplarto ethanol and co-products using an organosolv fractionationprocess optimization of process yieldsrdquo Biotechnology andBioengineering vol 94 no 5 pp 851ndash861 2006

[156] A Hideno A Kawashima T Endo K Honda and M MoritaldquoEthanol-based organosolv treatment with trace hydrochloricacid improves the enzymatic digestibility of Japanese cypress(Chamaecyparis obtusa) by exposing nanofibers on the surfacerdquoBioresource Technology vol 132 pp 64ndash70 2013

[157] M G Alriols A Garcıa R Llano-ponte and J Labidi ldquoCom-bined organosolv and ultrafiltration lignocellulosic biorefineryprocessrdquo Chemical Engineering Journal vol 157 no 1 pp 113ndash120 2010

[158] X Pan J F Kadla K Ehara N Gilkes and J N SaddlerldquoOrganosolv ethanol lignin from hybrid poplar as a radicalscavenger relationship between lignin structure extractionconditions and antioxidant activityrdquo Journal of Agricultural andFood Chemistry vol 54 no 16 pp 5806ndash5813 2006

[159] H Y Kim K S Gwak S Y Lee H S Jeong K O Ryu andI G Choi ldquoBiomass characteristics and ethanol production ofyellow poplar (Liriodendron tulipifera) treated with slurry com-posting and biofiltration liquid as fertilizerrdquo Biomass Bioenergyvol 42 pp 10ndash17 2012

[160] N Brosse R E L Hage P Sannigrahi and A RagauskasldquoDilute sulphuric acid and ethanol organosolv pretreatment ofmiscanthus x giganteusrdquo Cellulose Chemistry and Technologyvol 44 no 1ndash3 pp 71ndash78 2010

[161] Z Li Z Jiang B Fei et al ldquoEthanol organosolv pretreatment ofbamboo for efficient enzymatic saccharificationrdquo BioResourcesvol 7 no 3 pp 3452ndash3462 2012

[162] C Wang F Zhou Z Yang et al ldquoHydrolysis of celluloseinto reducing sugar via hot-compressed ethanolwatermixturerdquoBiomass and Bioenergy vol 42 pp 143ndash150 2012


[163] X Zhao K Cheng and D Liu ldquoOrganosolv pretreatmentof lignocellulosic biomass for enzymatic hydrolysisrdquo AppliedMicrobiology and Biotechnology vol 82 no 5 pp 815ndash827 2009

[164] Y N Guragain J De Coninck F Husson A Durand and SK Rakshit ldquoComparison of some new pretreatment methodsfor second generation bioethanol production from wheat strawand water hyacinthrdquo Bioresource Technology vol 102 no 6 pp4416ndash4424 2011

[165] S Han J Li S Zhu et al ldquoPotential applications of ionic liquidsin wood related industriesrdquo BioResources vol 4 no 2 pp 825ndash834 2009

[166] A P Dadi C A Schall and S Varanasi ldquoMitigation ofcellulose recalcitrance to enzymatic hydrolysis by ionic liquidpretreatmentrdquoApplied Biochemistry andBiotechnology vol 137ndash140 no 1ndash12 pp 407ndash421 2007

[167] M Mora-Pale L Meli T V Doherty R J Linhardt and J SDordick ldquoRoom temperature ionic liquids as emerging solventsfor the pretreatment of lignocellulosic biomassrdquo Biotechnologyand Bioengineering vol 108 no 6 pp 1229ndash1245 2011

[168] T Vancov A-S Alston T Brown and S McIntosh ldquoUse ofionic liquids in converting lignocellulosic material to biofuelsrdquoRenewable Energy vol 45 pp 1ndash6 2012

[169] HWu MMora-Pale J Miao T V Doherty R J Linhardt andJ S Dordick ldquoFacile pretreatment of lignocellulosic biomass athigh loadings in room temperature ionic liquidsrdquo Biotechnologyand Bioengineering vol 108 no 12 pp 2865ndash2875 2011

[170] N Muhammad Z Man M A Bustam M I A Mutalib CD Wilfred and S Rafiq ldquoDissolution and delignification ofbamboo biomass using amino acid-based ionic liquidrdquo AppliedBiochemistry and Biotechnology vol 165 no 3-4 pp 998ndash10092011

[171] J Holm and U Lassi Ionic Liquids in the Pretreatment of Ligno-cellulosic Biomass Ionic Liquids applications and perspectivesEdited by A Kokorin InTech 2011

[172] R Q Xie X Y Li and Y F Zhang ldquoCellulose pretreat-mentwith 1-methyl-3-ethylimidazoliumdimethylphosphate forenzymatic hydrolysisrdquo Cellulose Chemistry and Technology vol46 no 5-6 pp 349ndash356 2012

[173] S P M Ventura L D F Santos J A Saraiva and J A PCoutinho ldquoConcentration effect of hydrophilic ionic liquids onthe enzymatic activity of Candida antarctica lipase Brdquo WorldJournal of Microbiology and Biotechnology vol 28 pp 2303ndash2310 2012

[174] L Li S T Yu F S Liu C S Xie and C Z Xu ldquoEfficientenzymatic in situ saccharificatio of cellulose in aqeous-ionicliquid media by microwave treatmentrdquo BioResources vol 6 no4 pp 4494ndash4504 2011

[175] Z Zhang I M OrsquoHara and W O S Doherty ldquoPretreatmentof sugarcane bagasse by acid-catalysed process in aqueous ionicliquid solutionsrdquo Bioresource Technology vol 120 pp 149ndash1562012

[176] Q Wang Y Wu and S Zhu ldquoUse of ionic liquids for improve-ment of cellulosic ethanol productionrdquo BioResources vol 6 no1 pp 1ndash2 2011

[177] T V Doherty M Mora-Pale S E Foley R J Linhardt andJ S Dordick ldquoIonic liquid solvent properties as predictors oflignocellulose pretreatment efficacyrdquo Green Chemistry vol 12no 11 pp 1967ndash1975 2010

[178] A S Amarasekara and B Wiredu ldquoBronsted acidic ionicliquid 1-(1-propylsulfonic)-3-methylimidazolium-chloride cat-alyzed hydrolysisof D-cellobiose in aqueous mediumrdquo Interna-tional Journal of Carbohydrate Chemistry vol 2012 Article ID948652 6 pages 2012

[179] H Xie W Liu and Z K Zhao ldquoLignocellulose pretreatmentby ionic liquids a promising start point for bio-energy produc-tionrdquo Biomass Conversion pp 123ndash144 2012

[180] G Brodeur E Yau B Badal and J Collier ldquoChemical andphysicochemical pretreatment of lignocellulosic biomass areviewrdquo Enzyme Research vol 2011 Article ID 787532 17 pages2011

[181] X-F Tian Z Fang D Jiang and X-Y Sun ldquoPretreatment ofmicrocrystalline cellulose in organic electrolyte solutions forenzymatic hydrolysisrdquo Biotechnology for Biofuels vol 4 article53 2011

[182] S Singh B A Simmons and K P Vogel ldquoVisualizationof biomass solubilization and cellulose regeneration duringionic liquid pretreatment of switchgrassrdquo Biotechnology andBioengineering vol 104 no 1 pp 68ndash75 2009

[183] G Papa P Varanasi L Sun et al ldquoExploring the effectof different plant lignin content and composition on ionicliquid pretreatment efficiency and enzymatic saccharification ofEucalyptus globulus LMutantsrdquoBioresource Technology vol 117pp 352ndash359 2012

[184] B Li J Asikkala I Filpponen and D S Argyropoulos ldquoFactorsaffecting wood dissolution and regeneration of ionic liquidsrdquoIndustrial and Engineering Chemistry Research vol 49 no 5 pp2477ndash2484 2010

[185] A P Dadi S Varanasi and C A Schall ldquoEnhancement of cellu-lose saccharification kinetics using an ionic liquid pretreatmentsteprdquo Biotechnology and Bioengineering vol 95 no 5 pp 904ndash910 2006

[186] M Ungurean F Fitigau C Paul A Ursoiu and F PeterldquoIonic liquid pretreatment and enzymatic hydrolysis of woodbiomassrdquo World Academy of Science Engineering and Technol-ogy vol 76 pp 387ndash391 2011

[187] S Morales-delaRosa J M Campos-Martin and J L G FierroldquoHigh glucose yields from the hydrolysis of cellulose dissolvedin ionic liquidsrdquo Chemical Engineering Journal vol 181-182 pp538ndash541 2012

[188] PWeerachanchai S S J Leong MW Chang C B Ching andJ-M Lee ldquoImprovement of biomass properties by pretreatmentwith ionic liquids for bioconversion processrdquo Bioresource Tech-nology vol 111 pp 453ndash459 2012

[189] R Arora C Manisseri C Li et al ldquoMonitoring and ana-lyzing process streams towards understanding ionic liquidpretreatment of switchgrass (Panicum virgatum L)rdquo BioenergyResearch vol 3 no 2 pp 134ndash145 2010

[190] J A Perez-Pimienta M G Lopez-Ortega P Varanasi et alldquoComparison of the impact of ionic liquid pretreatment onrecalcitrance of agave bagasse and switchgrassrdquo BioresourceTechnology vol 127 pp 18ndash24 2013

[191] Z Zhi-Guo and C Hong-Zhang ldquoEnhancement of the enzy-matic hydrolysis of wheat straw by pretreatment with 1-allyl-3-methylimidazolium chloride ([Amim]Cl)rdquo African Journal ofBiotechnology vol 11 no 31 pp 8032ndash8037 2012

[192] M Lucas G LWagner Y Nishiyama et al ldquoReversible swellingof the cell wall of poplar biomass by ionic liquid at roomtemperaturerdquo Bioresource Technology vol 102 no 6 pp 4518ndash4523 2011


[193] G Cheng P Varanasi C Li et al ldquoTransition of cellulosecrystalline structure and surface morphology of biomass asa function of ionic liquid pretreatment and its relation toenzymatic hydrolysisrdquo Biomacromolecules vol 12 no 4 pp933ndash941 2011

[194] X-DHou T J Smith N Li andM-H Zong ldquoNovel renewableionic liquids as highly effective solvents for pretreatment of ricestraw biomass by selective removal of ligninrdquo Biotechnology andBioengineering vol 109 no 10 pp 2484ndash2493 2012

[195] D Yuan K Rao S Varanasi andR Relue ldquoA viablemethod andconfiguration for fermenting biomass sugars to ethanol usingnative Saccharomyces cerevisiaerdquo Bioresource Technology vol117 pp 92ndash98 2012

[196] Z Qiu G M Aita and M S Walker ldquoEffect of ionicliquid pretreatment on the chemical composition structureand enzymatic hydrolysis of energy cane bagasserdquo BioresourceTechnology vol 117 pp 251ndash256 2012

[197] T N Ang G C Ngoh A S M Chua and M G LeeldquoElucidation of the effect of ionic liquid pretreatment on ricehusk via structural analysesrdquo Biotechnology for Biofuels vol 5article 67 2012

[198] K Ninomiya T Yamauchi M Kobayashi et al ldquoCholiniumcarboxylate ionic liquids for pretreatment of lignocellulosicmaterials to enhance subsequent enzymatic saccharificationrdquoBiochemical Engineering Journal vol 71 pp 25ndash29 2013

[199] E Gnansounou ldquoProduction and use of lignocellulosicbioethanol in Europe current situation and perspectivesrdquoBioresource Technology vol 101 no 13 pp 4842ndash4850 2010

[200] E Tomas-Pejo P Alvira M Ballesteros and M J NegroldquoPretreatment technologies for lignocellulose-to-bioethanolconversionrdquo in Biofuels Alternative Feedstocks and ConversionProcesses A Pandey C Larroche S C Ricke C G Dussap andE Gnansounou Eds chapter 7 p 170 Elsevier 2011

[201] G Roslashdsrud M Lersch and A Sjode ldquoHistory and futureof worldrsquos most advanced biorefinery in operationrdquo BiomassBioenergy vol 46 pp 46ndash59 2012

[202] I M OrsquoHara L A Edye W O S Doherty and G KentDemonstration of Cellulosic Ethanol Production From SugarcaneBagasse in Australia The Mackay Renewable BiocommoditiesPilot Plant International Society of Sugar Cane TechnologistsVeracruz Mexico 2010

[203] X Q Zhao L H Zi F W Bai H L Lin X M Hao and GJ Yue ldquoBioethanol from lignocellulosic biomassrdquo Advances inBiochemical EngineeringBiotechnology vol 128 pp 25ndash51 2012

[204] S Hyvarinen P Virtanen D Y Murzin and J-P MikkolaldquoTowards ionic liquid fractionation of lignocellulosics for fer-mentable sugarsrdquo Cellulose Chemistry and Technology vol 44no 4-6 pp 187ndash195 2010

[205] J I Park E J Steen H Burd et al ldquoA thermophilic ionicliquid-tolerant cellulase cocktail for the production of cellulosicbiofuelsrdquo PLoS ONE vol 7 no 5 article e37010 2012

[206] H Guo X Qi L Li and R L Smith Jr ldquoHydrolysis of celluloseover functionalized glucose-derived carbon catalyst in ionicliquidrdquo Bioresource Technology vol 116 pp 355ndash359 2012

[207] S-J Kim A A Dwiatmoko J W Choi Y-W Suh D JSuh and M Oh ldquoCellulose pretreatment with 1-n-butyl-3-methylimidazolium chloride for solid acid-catalyzed hydroly-sisrdquo Bioresource Technology vol 101 no 21 pp 8273ndash8279 2010

[208] Z Zhu M Zhu and ZWu ldquoPretreatment of sugarcane bagassewith NH

4OH-H

2O2and ionic liquid for efficient hydrolysis

and bioethanol productionrdquoBioresource Technology vol 119 pp199ndash207 2012

[209] G Bokinsky P P Peralta-Yahya A George et al ldquoSynthe-sis of three advanced biofuels from ionic liquid-pretreatedswitchgrass using engineeredEscherichia colirdquoProceedings of theNational Academy of Sciences of theUnited States of America vol108 no 50 pp 19949ndash19954 2011

[210] M T Garcıa-Cubero G Gonzalez-Benito I Indacoechea MCoca and S Bolado ldquoEffect of ozonolysis pretreatment onenzymatic digestibility of wheat and rye strawrdquo BioresourceTechnology vol 100 no 4 pp 1608ndash1613 2009

[211] N Schultz-Jensen Z Kadar A B Thomsen H Bindslev andF Leipold ldquoPlasma-assisted pretreatment of wheat straw forethanol productionrdquo Applied Biochemistry and Biotechnologyvol 165 no 3-4 pp 1010ndash1023 2011

[212] R Travaini M D Otero M Coca R Da-Silva and SBolado ldquoSugarcane bagasse ozonolysis pretreatment effect onenzymatic digestibility and inhibitory compound formationrdquoBioresource Technology vol 133 pp 332ndash339 2013

[213] P Sannigrahi F Hu Y Pu and A Ragauskasa ldquoNovel oxidativepretreatment of Loblolly Pine Sweetgum and Miscanthus byozonerdquo Journal of Wood Chemistry and Technology vol 32 pp361ndash375 2012

[214] N Schultz-Jensen F Leipold H Bindslev and A B ThomsenldquoPlasma-assisted pretreatment of wheat strawrdquo Applied Bio-chemistry and Biotechnology vol 163 no 4 pp 558ndash572 2011

[215] D Rodriguez-Gomez L Lehmann N Schultz-Jensen A BBjerre and T J Hobley ldquoExamining the potential of plasma-assisted pretreated wheat straw for enzyme production byTrichoderma reeseirdquo Applied Biochemistry and Biotechnologyvol 166 pp 2051ndash2063 2012

[216] S K Uppal R Kaur and P Sharma ldquoOptimization of chemicalpretreatment and acid saccharification for conversion of sugar-cane bagasse to ethanolrdquo Sugar Tech vol 13 no 3 pp 214ndash2192011

[217] D Mishima M Tateda M Ike and M Fujita ldquoCompara-tive study on chemical pretreatments to accelerate enzymatichydrolysis of aquatic macrophyte biomass used in water purifi-cation processesrdquo Bioresource Technology vol 97 no 16 pp2166ndash2172 2006

[218] M Lucas S K Hanson G L Wagner D B Kimball and K DRector ldquoEvidence for room temperature delignification of woodusing hydrogen peroxide and manganese acetate as a catalystrdquoBioresource Technology vol 119 pp 174ndash180 2012

[219] G Banerjee S Car T Liu et al ldquoScale-up and integration ofalkaline hydrogen peroxide pretreatment enzymatic hydrolysisand ethanolic fermentationrdquo Biotechnology and Bioengineeringvol 109 no 4 pp 922ndash931 2012

[220] R-S Yao H-J Hu S-S Deng H Wang and H-X ZhuldquoStructure and saccharification of rice straw pretreated withsulfur trioxide micro-thermal explosion collaborative dilutesalkalirdquo Bioresource Technology vol 102 no 10 pp 6340ndash63432011

[221] F Li R Yao HWang H Hu and R Zhang ldquoProcess optimiza-tion for sugars production from rice straw via pretreatmentwithsulphur trioxide micro-thermal explosionrdquo BioResources vol 7no 3 pp 3355ndash3366 2012

[222] P Sannigrahi A J Ragauskas and S JMiller ldquoChlorine dioxidetreatment of biomass feedstockrdquo US Patent Application Pub-lishing Patent No US 8 497 097 B2 2012

[223] L Bu Y Xing H Yu Y Gao and J Jiang ldquoComparative studyof sulfite pretreatments for robust enzymatic saccharification ofcorn cob residuerdquo Biotechnology for Biofuels vol 5 article 82012


[224] Y Jin L YangH Jameel HMChang andR Phillips ldquoSodiumsulfite-formaldehyde pretreatment of mixed hardwoods and itseffect on enzymatic hydrolysisrdquoBioresource Technology vol 135pp 109ndash115 2013

[225] Q Li Y Gao H Wang and B Li ldquoComparison of differ-ent alkali-based pretreatments of corn stover for improvingenzymatic saccharificationrdquoBioresource Technology vol 125 pp193ndash199 2012

[226] K-K Cheng W Wang J-A Zhang Q Zhao J-P Li andJ-W Xue ldquoStatistical optimization of sulfite pretreatment ofcorncob residues for high concentration ethanol productionrdquoBioresource Technology vol 102 no 3 pp 3014ndash3019 2011

[227] J Y Zhu W Zhu P Obryan et al ldquoEthanol production fromSPORL-pretreated lodgepole pine preliminary evaluation ofmass balance and process energy efficiencyrdquo Applied Microbi-ology and Biotechnology vol 86 no 5 pp 1355ndash1365 2010

[228] D S Zhang Q Yang J Y Zhu and X J Pan ldquoSulfite (SPORL)pretreatment of switchgrass for enzymatic saccharificationrdquoBioresource Technology vol 129 pp 127ndash134 2013

[229] L Shuai Q Yang J Y Zhu et al ldquoComparative study of SPORLand dilute-acid pretreatments of spruce for cellulosic ethanolproductionrdquo Bioresource Technology vol 101 no 9 pp 3106ndash3114 2010

[230] Q Yang and X Pan ldquoPretreatment of Agave americana stalk forenzymatic saccharificationrdquoBioresource Technology vol 126 pp336ndash340 2012

[231] H Liu and J Y Zhu ldquoEliminating inhibition of enzymatichydrolysis by lignosulfonate in unwashed sulfite-pretreatedaspen using metal saltsrdquo Bioresource Technology vol 101 no 23pp 9120ndash9127 2010

[232] G P da Silva M Mack and J Contiero ldquoGlycerol a promis-ing and abundant carbon source for industrial microbiologyrdquoBiotechnology Advances vol 27 no 1 pp 30ndash39 2009

[233] F Yang M Hanna and R Sun ldquoValue-added uses for crudeglycerolmdasha byproduct of biodiesel productionrdquo Biotechnologyfor Biofuels vol 5 article 13 2012

[234] H Zhao J H Kwak Y Wang J A Franz J M Whiteand J E Holladay ldquoInteractions between cellulose and N-methylmorpholine-N-oxiderdquo Carbohydrate Polymers vol 67no 1 pp 97ndash103 2007

[235] Q Li G-S Ji Y-B Tang X-D Gu J-J Fei and H-QJiang ldquoUltrasound-assisted compatible in situ hydrolysis ofsugarcane bagasse in cellulase-aqueous-N-methylmorpholine-N-oxide system for improved saccharificationrdquo BioresourceTechnology vol 107 pp 251ndash257 2012

[236] M Shafiei K Karimi and M J Taherzadeh ldquoPretreatment ofspruce and oak byN-methylmorpholine-N-oxide (NMMO) forefficient conversion of their cellulose to ethanolrdquo BioresourceTechnology vol 101 no 13 pp 4914ndash4918 2010

[237] A Goshadrou K Karimi and M J Taherzadeh ldquoEthanoland biogas production from birch by NMMO pretreatmentrdquoBiomass Bioenergy vol 49 pp 95ndash101 2013

[238] N Poornejad K Karimi and T Behzad ldquoImprovement ofsaccharification and ethanol production from rice straw byNMMO and [BMIM][OAc] pretreatmentsrdquo Industrial Cropsand Products vol 41 pp 408ndash413 2013

[239] P R Lennartsson C Niklasson and M J Taherzadeh ldquoA pilotstudy on lignocelluloses to ethanol and fish feed using NMMOpretreatment and cultivation with zygomycetes in an air-liftreactorrdquo Bioresource Technology vol 102 no 6 pp 4425ndash44322011

[240] M Shafiei K Karimi and M J Taherzadeh ldquoTechno-economical study of ethanol and biogas from spruce wood byNMMO-pretreatment and rapid fermentation and digestionrdquoBioresource Technology vol 102 no 17 pp 7879ndash7886 2011

[241] J C Lopez-Linares I Romero M Moya et al ldquoPretreatmentof olive tree biomass with FeCl

3prior enzymatic hydrolysisrdquo

Bioresource Technology vol 128 pp 180ndash187 2013[242] H Li and J Xu ldquoOptimization of microwave-assisted calcium

chloride pretreatment of corn stoverrdquo Bioresource Technologyvol 127 pp 112ndash118 2013

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



known that cellulase loadings of less than 10 FPUgram-cellulose are essential for economic production of cellulosicethanol [14]

In fermentation sugars are converted into ethanol underliquid- or solid-state using yeast or bacteria The processeconomics is improved significantly if both C5 and C6sugars are utilized though the fermentation efficiency of C5sugars is very low Further the yeasts cannot endure lowpH as well as high ethanol and byproduct concentrations[15] Additional challenges with xylose fermenting yeastsinclude long fermentation periods low productivity highviscosity of fermentation broth and byproduct formation[15] For both enzymatic hydrolysis and fermentation thepresence of degradation compounds such as furfural andhydroxymethyl-furfural (HMF) produced during pretreat-ment inhibits the smooth functioning of enzymes Thusongoing research under pretreatment has focussed on thedevelopment of innovativemethods requiring the use of mildconditions that significantly reduce inhibitor formationwhilemaintaining high sugar yields

In general pretreatment presents the most practicaland economic challenges in the attempt to commercializecellulosic bioethanol [16ndash18] since it may affect upstream [14]as well as downstream processes by determining fermenta-tion toxicity enzymatic hydrolysis rates enzyme loadingsproduct concentrations and purification waste treatmentdemands and power generation [19] The results from manystudies have shown that pretreatment is relatively costlyamong the various operations and processes involved incellulosic ethanol production [20ndash25] representing about20 of the total cost [14] While pretreatment introducesadditional cost the consequence of hydrolysing lignocellu-lose without pretreatment is far less favourable since onlyabout 20 of native biomass is hydrolysed [26]

It is generally accepted that efficient pretreatment shouldavoid size reduction and use of costly chemicals [19 27]improve fibre reactivity and maximize formationrecoveryof sugars [28] avoid loss of carbohydrate [29] avoid for-mation of enzyme-inhibiting byproducts [30 31] preservecellulose and hemicellulose fractions that are easily digestibleby hydrolytic enzymes [32 33] generate high-value lignincoproduct [18 26] minimize energy requirement [22 34]and achieve high sugar yields under high biomass loads[35] However no perfect pretreatment method has beendiscovered since there are variations in terms of suitability ofonemethod for variousmaterials whichmay be further com-pounded by factors such as maturity mode of harvest extentof drying and storage conditions of the feedstock [36ndash39]The chemicalmethods of pretreating lignocellulosicmaterialsare widely employed in many pilot and demonstration plantssince they are ideal for low lignin materials This paperreviews the various chemical methods that have receivedsignificant attention globally with emphasis on process inno-vations and interesting findings from the work of researchersin the field It is the second of two papers (with the firstarticle addressing physical and physicochemical methods)that is expected to serve as a reference for researchers in bothacademia and industry The methods discussed are centredon the use of acids bases oxidants and solvents

2 Chemical Pretreatment ofLignocellulosic Biomass

21 Acid Hydrolysis In this method dried biomass is milled(occasionally) presoaked in water and submerged in acidicsolution under specific temperatures for a period of timePretreated content is filtered to separate the liquor from theunhydrolysed solid substrate which undergoes washing (toextract sugars and remove acids) andor neutralization beforesaccharification Generally the hydrogen ion concentrationis directly correlated with the hydrolysis reaction constantthus the more negative the pKa value of the acid the moreeffective the hydrolysis process [40] Sulphuric (H

2SO4) and

phosphoric (H3PO4) acids are widely used since they are

relatively cheap and efficient in hydrolysing lignocellulosethough the latter gives a milder effect and is more benignto the environment Hydrochloric (HCl) acid is more volatileand easier to recover and attacks biomass better than H

2SO4

[41] similarly nitric acid (HNO3) possesses good cellulose-

to-sugar conversion rates [42] However both acids areexpensive compared to sulphuric acid

In acidic media the amorphous hemicelluloses in LBhydrolyse quicker (than cellulose) to soluble sugars [4344] and some oligomers especially in mild conditions [21]through the disruption of xylosidic bonds and cleavage ofacetyl ester groups [45 46] and the lignin seal is degradedthrough substitution reactions and broken links accom-panied by condensation reactions that prevent dissolution[47 48] Cellulose undergoes preferential degradation ofamorphous regions leading to enlarged cellulose fibrils andfibril aggregates [44] and an increase in the crystallinity indexof the pretreated material [38 43]

The process is generally affected by particle size temper-ature reaction time acid concentration and liquid-to-solidratio The combined severity factor (1198771015840

0) is an index used to

assess the effect of pretreatment temperature time and pHon the efficiency of the process as shown below [49]

log11987710158400= log (119905 sdot 119890(119879minus100)1475) minus pH (1)

where 119905 is the reaction time inminutes and119879 is the hydrolysistemperature in ∘C Acid pretreatment comes under two mainvariationsmdashdilute and concentrated acid hydrolysis eachapplied under further process variations

211 Dilute Acid Pretreatment Under dilute acid (02ndash25ww) processes high temperatures (120ndash210∘C) and pressuresare used to achieve reaction times in seconds or minutes andare thus suitable for continuous operations [21 50] The lowacid consumption is a major advantage in terms of cost andprocess severity [51]Moreover low acid concentrations (lt1wv sulphuricphosphoric) release essential nutrients (S andP) that enhance downstream fermentation [52] A variationof the process involves two stages of pretreatment in thefirst stage most hemicelluloses in the biomass substrate aresolubilised in the presence of a more dilute acid while thesecond stage involves the use of a higher acid concentrationto hydrolyse the cellulose and the remaining hemicellulose[53 54]



2SO4 HNO

3


3pretreat-






2SO4















2from the fermenter






















2SO4and NaOH









3using CO



2[21]






2and H

2O







2 15min


2O210 bar air

[140]



2SO4 etc)




2SO4) basic (NaOH)






























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2SO4 HNO

3


3pretreat-






2SO4















2from the fermenter






















2SO4and NaOH









3using CO



2[21]






2and H

2O







2 15min


2O210 bar air

[140]



2SO4 etc)




2SO4) basic (NaOH)






























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














2from the fermenter






















2SO4and NaOH









3using CO



2[21]






2and H

2O







2 15min


2O210 bar air

[140]



2SO4 etc)




2SO4) basic (NaOH)






























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












2SO4and NaOH









3using CO



2[21]






2and H

2O







2 15min


2O210 bar air

[140]



2SO4 etc)




2SO4) basic (NaOH)






























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2 15min


2O210 bar air

[140]



2SO4 etc)




2SO4) basic (NaOH)






























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation




























4OH-H







2
















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation





















2O2) peracetic acid





2O2 Mishima







3) and NaOH



3will be








2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














2SO3at 140∘C









2O system and the




Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table2Selected

large-scalec

ellulosic

ethano

lplantsb

ased

onchem

icalpretreatment

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

SEKA

BOrnskoldsvik

Sweden

100ty

Twosta

gedilute

H2SO

4SO

2Pine

chips

Operatio

nal

since

2004

scale-up

projects

planned

[199]

Upd

ated

Abengoa

bioenergy

Salamanca

Spain

5mLy

Acid

impregnatio

n+ste

amexplosion

Wheatandbarle

ystr

awand

soforth

Operatio

nal

since

2009

httpwwwkccs

tateksu


bbpdf

(accessed110213)

YorkN

EUSA

04m

Ly

Cornsto

ver

Operatio

nal

since

2008

KansasU

SA25

mgaly

Cornsto

verwheat

straw

switchgrass

andso

forth

Und

erconstructio

nsta

rtup

2014

BioG

asol

Ballerup

Denmark

4th

Dilu

teacidsteam

explosionor

wet

explosion

Wheatstr

awand

brancornsto

ver

andso

forthgarden

wastesenergy

crop

sandgreenwastes

Und

erdevelopm

ent

httpwwwbiogasolco

mH

ome-3aspx

(accessed110213)

Procetho

l2G

Futurol

Pomacle

France

180m

3 y

35m

Ly

180m

Ly

Und

erdevelopm

ent

Wheatstr

aw

switchgrassgreen

wasteM

iscanthus

Vinassesand

soforth

Operatio

nal

since

2011

Planned2015

Planned2016

httpwwwprojet-fu

turolcom

index-uk

php

(accessed130213)

Izum

iBiorefinery

Japan

300L

day

Arkenol

Cedarpineand

hemlock

Operatio

nal

since

2002

[200]

httpbfreincc

omdocsIZUMIStatus

2004

forBlueFire

051606pdf

(accessed130213)

INEO

SFloridaUSA

8mgaly

rTh

ermochemical

Mun

icipalsolid

wasteandso

forth

Operatio

nal

httpwwwineosbioco

m60-Techno

logy

platform

htm

(accessed

110213)

ZeaC

hem

Oregon

USA

25000

0galy

Chem

ical

Hybrid

poplarcorn

stoverandcob

Con

structio

ncompleted

httpwwwzeachemco

min

dexph

p(accessed120213)

Logos

Techno

logies

CaliforniaUSA

50000

galy

Colloid

milling

Cornsto

ver

switchgrassand

woo

dchips

Operatio

nal

httpwwwlogos-techno

logiesco

m(accessed

130213)

BlueFire

Mississippi

USA

19mgaly

Con

centratedacid

(Arkenol)

Woo

dwaste

mun

icipalsolid

waste

Und

erconstructio

nhttpbfreincc

om(accessed

150213)

Weyland

AS

Norway

200m

3 y

Con

centratedacid

Cornsto

versawdu

stpaperp

ulp

switchgrassand

soforth

Operatio

nal

since

2010

httpweyland

no

(accessed150213)

Borregaard

Norway

20mLy

Acidicneutral

sulphite

Wheatstr

aw

eucalyptusspruce

andso

forth

Operatio

nal

[201]httpwwwbo

rregaardco

m(accessed

110213)


Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table2Con

tinued

Com

pany

institu

tion

Locatio

nCa

pacitylowast

Pretreatment

Feedsto

ckStatus

Reference

Queensla

ndUniversity

ofTechno

logy

Queensla

nd

Austr

alia

Pilot

Acidalkaline

steam

explosion

ionicliquidandso

forth

Sugarcaneb

agasse

Operatio

nal

since

2010

[202]

Prajindu

strie

sIndia

10mLy

Thermochemical

Corncobsugarcane

bagasseandso

forth

Und

erdevelopm

ent

[200](Upd

ated)

Lign

olEn

ergy

Corpo

ratio

nCa

nada

100m

3 y

Organosolv

Woo

dagric

ultural

resid

uesandso

forth

Operatio

nal

httpwwwligno


40ndash200

mLy

Planning

Blue

sugars

WyomingUSA

14mgaly

Acid

thermom

echanical

Pine

andso

forth

Operatio

nal

httpbluesugarsco

m(accessed

130213)

Petro

brasBlue

sugars

Brazil

10mgaly

Acid

thermom

echanical

Sugarcaneb

agasse

Und

erdevelopm

ent

httpbluesugarsco

mcom

pany-partnerwith

htm

(accessed160213)

Dup

ont

Danisc

oCellulosic

Ethano

l(D

DCE

)

IowaUSA

30mgaly

NH

3Steam

recycle

dCornsto

ver

Und

erconstructio


pontco

m(accessed

130213)

COFC

OSIN

OPE

CN

ovozym

e

Zhaodo

ng

China

62mLy

Steam

explosion

(with

acid

impregnatio

n)Cornsto

ver

Und

erconstructio

n[203]

lowastPilot(lt2000

tyor

25m

m3 y)dem

o(200

0ndash50000

tyor

25ndash65

mm

3 y)com

mercial(gt50000

tyor

65mm

3 y)











Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation



















Acknowledgment


References



























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation





























































































































































































































4OH-H










































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation

































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









alkaline distillation problem.pdf

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