MINI-REVIEW
Production of biogas from solid organic wastesthrough anaerobic digestion: a review
Ismail Muhammad Nasir & Tinia I. Mohd Ghazi &Rozita Omar
Received: 16 December 2011 /Revised: 3 May 2012 /Accepted: 3 May 2012 /Published online: 24 May 2012# Springer-Verlag 2012
Abstract Anaerobic digestion treatments have often beenused for biological stabilization of solid wastes. These treat-ment processes generate biogas which can be used as arenewable energy sources. Recently, anaerobic digestion ofsolid wastes has attracted more interest because of currentenvironmental problems, most especially those concernedwith global warming. Thus, laboratory-scale research on thisarea has increased significantly. In this review paper, thesummary of the most recent research activities coveringproduction of biogas from solid wastes according to itsorigin via various anaerobic technologies was presented.
Keywords Anaerobic digestion . Biogas . Methane .
Solid waste
Introduction
Million tons of solid waste are produced annually frommunicipal, industrial, and agricultural sources. The indis-criminate decomposition of these organic wastes results inlarge-scale contamination of land, water, and air. Of all theforms of solid organic waste, the most abundant is animaldung primarily from small farms, and it is from these farmsthat the pollution problem originating from waste disposal ismore intense. Research continues to focus on the treatmentof cattle dung for biogas production and possible optimiza-tion methods which could be used to enhance the productionfor practical applicability of the technology. Omar et al.(2008) observed an improvement in biogas yield up to
0.207 m3 kg−1 VS added with average methane content of65 % in the anaerobic treatment of cattle manure by additionof palm oil mill effluent as an inoculum in a laboratory scalebioreactor. In another study, Ounaar et al. (2012) obtainedbiogas production of 26.9 m3 with an average methanecontent of 61 % during the anaerobic digestion of 440 kgof cow dung with an energy equivalent of 164.5 kWh. Theseresults are encouraging for the use of animal waste availableto produce renewable energy and clean environment.
According to Yu et al. (2002), decomposition of 1 MT ofgrass waste can possibly release 50–110 m3 of carbon diox-ide and 90–140 m3 of methane into the atmosphere. Meth-ane is an important greenhouse gas with the ability of globalwarming 25 times greater than that of carbon dioxide, andits atmospheric concentration has been increasing in therange of 1 to 2 % per year (IPCC 2007). Conventionalmunicipal solid waste (MSW) management has been mainlydisposal by land filling (Sosnowski et al. 2003). However,waste from landfills has been identified as the major sourceof anthropogenic methane emission and an essential con-tributor to global warming (IPCC 1996). Therefore, theincreased production of MSW accompanied with environ-mental and economic difficulties facing the conventionalmethods of disposal have resulted in great efforts to findalternative methods of disposal (Zsigraiova et al. 2009). Themost promising alternative to incinerating and compostingthese solid wastes is to digest its organic matter employingthe anaerobic digestion (Bouallagui et al. 2005).
Anaerobic digestion for biogas production has become aworldwide focus of research, because it produces energythat is renewable and environmentally friendly. Special em-phasis was initially focused on anaerobic digestion of MSWfor bioenergy production about a decade ago (Braber 1995;Kiely et al. 1997). Anaerobic biological treatment can be anacceptable solution because it reduces and stabilizes solid
I. Muhammad Nasir : T. I. Mohd Ghazi (*) : R. OmarDepartment of Chemical and Environmental Engineering,Faculty of Engineering, Universiti Putra Malaysia,43400 Serdang, Selangor, Malaysiae-mail: [email protected]
Appl Microbiol Biotechnol (2012) 95:321–329DOI 10.1007/s00253-012-4152-7
wastes volume, produces biogas comprising mainly meth-ane and carbon dioxide, and traces amount of other gases(Stroot et al. 2001). In addition to biogas, a nutrient-richdigestate is also produced which provide either fertilizer orsoil conditioner properties. Biological treatment of MSW tobiogas by anaerobic digestion processes including source-sorted and mechanically sorted MSW has been previouslydiscussed (Gunaseelan 1997).
Literature is available about the applications and impor-tance of the anaerobic digestion treatments for solid wastetreatment, especially focusing on promoting process effi-ciency and performance. Therefore, the main objective ofthis review paper is to summarize the research activities onthe effects of both operational and process performanceparameters, covering the anaerobic conversion of varioussolid waste substrates via various anaerobic systems.
Production of biogas by anaerobic digestion processes
Many research papers have been published regarding theperformance of different anaerobic technological systemsdigesting organic solid wastes. Most of them concentrateon the concept of anaerobic digestion of the organic fractionof municipal solid waste (OFMSW). Anaerobic treatment ofOFMSW has been an attractive feedstock for biogas pro-duction. Nevertheless, pretreatment of MSW before thedigestion is the initial stage, and these wastes are character-ized by a high percentage of moisture and VS above 90 %with high biodegradability. Rao et al. (2000) referred tothese wastes as municipal garbage, which is the main con-stituent of MSW (40–45 wt.%), emanating from differentsources as food waste (FW) such as households, fruit andvegetable markets, canteens, hotels, etc., and they are rich inorganic matter and can be used for biogas generation byanaerobic digestion. Anaerobic digestion of solid organicwastes has been studied recently, attempting to developtechnology that offers waste stabilization accompanyingresources recovery. About 90 % of the full-scale plant pres-ently in operation in Europe for anaerobic digestion ofOFMSW relies on one-stage system, and this are dividedinto wet and dry digestion (De Baere 2000). A likely reasonfor this is that the industrialists prefer a one-stage systemover the two-stage or multistage systems because a simplerdesign system suffers less frequent technical failures and areeconomical. The dry digestion systems digest waste asreceived, while the wet digestion systems need to slurrythe waste with water to about 12 % TS (Vandevivere et al.2002). However, from a technical point of view, the drydigestion systems appear more robust as regular technicalfailures are reported with wet systems due to sand, plastics,wood, and stones. Many researchers have already reportedvarious studies on laboratory scale, pilot-scale, and full-
scale anaerobic digestion for the treatment of organic solidwaste. From a review of literature on the preliminary designprocedure for anaerobic digesters for the treatment of MSWfor biogas production, Igoni et al. (2008) noted that properreactor size reduction must be considered for the anaerobicdigestion of organic wastes. They further explained that themost important aspect of digestion processes, such as, tem-perature, hydrogen ion concentration, carbon nitrogen (C/N)ratio, organic loading rate (OLR), moisture content, and heatcontent, need to be manipulated so as to achieve optimalperformance for anaerobic digester. They recommend thatthe batch digestion system should be increasingly employedbecause it is cost-effective and economical for treating theever abundant MSW to useful energy. Therefore, a summaryof the anaerobic digestion processes employed for thesewastes will be showed in this section, and the overview ofthe studies are also presented in an orderly manner in Table 1.
A laboratory scale batch anaerobic digestion of municipalgarbage was studied by Rao et al. (2000) at temperatures of25 °C and 29 °C, with a concentration range between 45 and135 g TS/L. They found out that the methane content fromthe biogas varied between 62 and 72 %, and a conversionefficiency of about 85 % was obtained. In a similar study,Rao and Singh (2004) investigated the batch digestion ofmunicipal garbage under room temperature (26±4 °C) toestimate its bioenergy potential and conversion efficienciesat an HRT of 15 days. They reported a high yield of 0.56 m3
biogas kg−1 VS added with 70 % methane content and a VSreduction of 76.3 %. These results demonstrated that mu-nicipal garbage has a high potential to be a bioenergysource. López and Espinosa (2008) evaluated the effect ofpretreating OFMSW with lime in the anaerobic digestionprocess. The laboratory scale experiment was carried out ina completely mixed reactor operated on a batch basis. Themaximum yield of methane obtained under the anaerobicdigestion of the pretreated waste was 0.15 m3 kg−1 VSadded. This result is nearly 172 % increase in the methaneyield over the control without pretreatment. In addition,under the same condition, soluble COD and VS removalwere 93 and 94 %, respectively. The outcome implied thatthe chemical pretreatment with lime, followed by anaerobicdigestion, gives the best result for OFMSW stabilization.Elango et al. (2007) reported data on the influence of do-mestic sewage on the biogas production from municipalsolid waste using the anaerobic digestion process. Theyoperated a batch reactor at temperatures from 26 to 36 °Cwith a fixed HRT of 25 days and different OLR in the rangeof 0.5 to 4.3 kg VS m3 day−1. They obtained a maximumamount of biogas production of 0.36 m3 kg−1 VS added atOLR of 2.9 kg VS m3 day−1. This OLR was referred to asthe optimum OLR because the maximal removal of TS(87 %), VS (88.15), and COD (89.3 %) occurred at thisstage. They concluded that the disposal problem of MSW
322 Appl Microbiol Biotechnol (2012) 95:321–329
Tab
le1
Operatio
nalandperformance
data
fordifferentbioreactor
design
sappliedforsolid
wastes
Researcher
Reactor
type
andvolume
Feed
Tem
p.(°C)
OLR
(kgVSm
−3days
−1)
HRT(days)
Efficiency
VSRED(%
)CH4yield
(m3kg
−1VSadded)
Biogasyield
(m3kg
−1VS)
%CH4
Rao
etal.(200
0)Batch
MSW
25and29
NA
NR
85NR
NR
72
Rao
andSingh
(200
4)Batch
(3.25L)
MSW
25NA
1576.3
NR
0.56
070
Lop
ezandEspinosa(2008)
Batch
(1L)
OFMSW
25NA
NR
940.15
NR
NR
Elang
oet
al.(200
7)Sem
icont.batch(5
L)
MSW
+domestic
sewage
26–36
05-4.3
2588.1
NR
0.36
68–72
Fernand
ezet
al.(2008)
Batch
(1.7
L)
OFMSW
35NA
NR
NR
0.11
(20%
TS);
0.00
7(30%
TS)
NR
NR
Fernand
ezet
al.(2010)
Batch
(1.7
L)
OFMSW
35NA
15(20%
TS);
35(30%
TS)
NR
NR
NR
80(20%
TS)
Guend
ouzet
al.(2010)
Highsolid
batch(40L)
MSW
35NA
1540
0.211
NR
NR
Paraw
iraet
al.(200
4)Batch
(0.5
L)
Potatowaste/potato
waste
+beet
leaves
37NA
14NR
0.42
/0.68
NR
62/84
Macias-Coral
etal.(2008)
UAF(222
L)
OFMSW
+CM
/CGW
+CM
NR
NR
141/151
NR
0.1/0.19
NR
72
Fernand
ezet
al.(2005)
Sem
icont.(14L)
OFMSW
370.97
1773
0.3
0.8
58
Ngu
yenet
al.(200
7)Batch
(375
L)
Leachate
37NR
6061
0.26
NR
55
Hartm
annandAhring(2005)
CSTR(4.5
L)
OFMSW
+CM
554
1874
0.46
00.71
064
Linke
(200
6)CSTR
Potatoprocessing
waste
550.8–3.4
NR
NR
NR
0.65
–0.85
58
Glass
etal.(200
5)CSTRandAF
Steam
-treated
OFMSW
NR
NR
1220
%COD,86
%COD
(CSTR,AF)
NR
0.02
–0.29
,0.04
–
0.47
(CSTR,AF)
NR
Sosno
wskiet
al.(2003)
2-stageCSTRand
UASB
Sew
agesludge
+OFMSW
56,36
(CSTR,U
ASB)
0.669gVSS
dm−3day−
117.3,44.2
(CSTR,UASB)
NR
0.02
4NR
60
Fon
gsatitk
ulet
al.(2010)
2-stge
OFMSW
+RAS
35NR
2878
NR
0.73
NR
Bou
allagu
iet
al.(2003)
Tubular
reactor(18L)
FVW
356%
TS
2075.9
NR
0.70
757
Bou
allagu
iet
al.(2004)
2-phasesystem
(18L)
FVW
35/55
7.5kg
COD
m−3day−
120
96%
COD
NR
0.70
5,0.99
7(35and55
°C)
64,61
(35and55
°C)
Zhang
etal.(200
7)Batch
system
Foodwaste
50NA
10/28
810.34
8,0.43
5(10,
28days)
NR
73
Forster-Carneiroet
al.(2007b
)Batch
FW
35NR
20–60
NR
NR
0.49
NR
Bou
allagu
iet
al.(2009)
ASBR(2
L)
FVW
551.24
2079
NR
0.48
060
Bou
allagu
iet
al.(2009)
ASBR(2
L)
Abatto
irwaste
+FVW
552.56
2086.2
NR
0.73
62
Alvarez
andLiden
(2008)
Sem
icont.(2
L)
FVW
+SW
+manure
351.3
30NR
0.32
01.36
056
Schob
eret
al.(199
9)1–
stageand2-stage
(30L)
KR
35/55
611
72,80
(35and55
°C)
NR
0.80
0,0.83
0(35and55
°C)
NR
Paraw
iraet
al.(200
6)UASB(0.84L)and
APB
(0.7
L)
PW
leachate
(UASB),
PW
(APB)
376.1,
4.7
(UASB,APB)
13.2,10
(UASB,APB)
NR
NR
NR
59,66
(UASB,APB)
Ang
elidakiet
al.(2006)
CSTR(4.5
L)
SS-O
FMSW
5511.4
1530
0.43
00.71
64
Davidsson
etal.(2007)
Pilo
t-scale(35L)
SS-O
FMSW
552.8
1581
0.3–0.4
NR
62
Forster-Carneiroet
al.(2008a)
Batch
(5L)
SS-O
FMSW/M
S-
OFMSW
55NA
6056
NR
NR
53.4
Marou
nandELFadel
(2007)
CSTR(10.4L)
SS-O
FMSW
352.03
90NR
NR
0.2–
0.56
40–65
Kim
etal.(200
6)3-stagesemicont.
Foodwaste
50NR
12.4
NR
NR
NR
67.4
Forster-Carneiroet
al.(2008c)
Batch
(1.1
L)
FW/SH-O
FMSW/
OFMSW
55NR
9032.4/73.7/79
.40.18
/0.05/0.08
NR
NR
Forster-Carneiroet
al.(2007)
Batch
(1.1
L)
SS-O
FMSW,food
waste
55NA
9074,32.4
(SS-O
FMSW,FW)
0.50
,0.18
0(SS-O
FMSW,FW)
NR
68.5,76
.7(SS-O
FMSW,FW)
Sharm
aet
al.(200
0)PFR(1350L)
SSW
3740
33.7
710.7
1.05
NR
Appl Microbiol Biotechnol (2012) 95:321–329 323
and domestic sewage can be resolved substantially. Anexperiment was performed by Fernandez et al. (2008) toinvestigate the influence of substrate concentration on drymesophilic anaerobic digestion of the OFMSW. The exper-iment was conducted in a batch reactor at 35 °C, during aperiod of 85–95 days at solid concentrations of 20 % and30 % TS. Experimental results indicated that the reactorwith 20 % TS achieved a higher yield of 0.11 m3 CH4
kg−1 VS removed compared to 0.07 m3 CH4 kg−1 VSremoved achieved for 30 % TS reactor. Also, the 20 % TSdigestion attained the highest performance with high dis-solve organic carbon (DOC) removal (80.69 %), comparedto the 30 % TS digestion (69.05 %). Therefore, they con-cluded that the initial substrate concentration during theanaerobic digestion of OFMSW affects the process clearly.In a similar study, Fernandez et al. (2010) investigated themesophilic anaerobic degradation of OFMSW in discontin-uous lab reactors with two different initial concentrations of20 % TS and 30 % TS. The anaerobic treatment was favoredwhen it was conducted with a 20 % TS content in compar-ison to a similar process with 30 % TS. Results showed ahigher level of organic matter removed, in terms of DOCand VFA, 18.18 % and 8.09 %, respectively, in the 20 % TSsystem. Also, the kinetics parameters demonstrated higheractive biomass and a higher coefficient for the production ofmethane at the 20 % TS concentration.
Guendouz et al. (2010) found similar biogas and methaneyields of around 0.211 m3 kg−1 VS added with 40 % VSreduction conducted in a laboratory scale high-solid batchdigestion test of MSW under mesophilic conditions for a15-day HRT. The results obtained compared well to a largerpilot-scale reactor operation with a yield of 0.205 m3 meth-ane kg−1 VS added. Parawira et al. (2004) examined batchanaerobic codigestion in an experiment with different mix-tures of potato waste and beet leaves. They reported anenhanced yield of 0.68 m3 methane kg−1 VS added with amixing ratio of (24:16%TS), and another yield of 0.42 m3
methane kg−1 VS added from potato waste alone. Theprocesses were both operated under mesophilic conditionsat an HRT of 14 days. The codigestion result showed anoptimum mixing ratio for successful operation with a higheryield and a shorter HRT. Hence, the batch anaerobic diges-tion can be applied where low cost and low technology areneeded.
Macias-Coral et al. (2008) investigated the applicabilityof a two-phase pilot-scale anaerobic codigestion system forthe treatment of OFMSW, dairy cow manure (CM), andcotton gin waste (CGW). Results showed that the singlewaste digestion of OFMSW and CM produced 0.03 and0.08 m3 CH4 kg−1 VS added. Meanwhile, the codigestionof OFMSW and CM produced a yield of 0.1 m3 kg−1 VSadded, in addition to the CGW and CM which obtained thehighest yield of 0.19 m3 kg−1 VS added. They concludedT
able
1(con
tinued)
Researcher
Reactor
type
andvolume
Feed
Tem
p.(°C)
OLR
(kgVSm
−3days
−1)
HRT(days)
Efficiency
VSRED(%
)CH4yield
(m3kg
−1VSadded)
Biogasyield
(m3kg
−1VS)
%CH4
Lastella
etal.(2002)
PFR(1350L)
SSW
3760
22.5
72NR
NR
68
Bolzonella
etal.(2006)
Fullscale(2,200
m3)
SS-O
FMSW
mixture
36–39
4–6
40–60
780.4
NR
56
Zup
ancicet
al.(2008)
Fullscale(2,000
m3)
OW
+sludge
350.8
20NR
0.39
–0.6
NR
NR
Semicont.sem
i-continuo
us,C
STRcontinuo
usstirredtank
reactor,MSW
mun
icipalsolid
waste,F
VW
fruitandvegetablewaste,S
Wslaugh
terho
usewaste,S
SWsemisolid
waste,C
GW
cotto
ngin
waste,C
Mcattlemanure,KRkitchenrefuse,P
Wpo
tato
waste,R
ASreturn
activ
ated
slud
ge,S
SWsemisolid
waste,S
S-OFMSW
source
sorted
organicfractio
nof
mun
icipalsolid
waste,O
Worganic
waste,Temp.
temperature,OLRorganicloadingrate,HRThy
draulic
retentiontim
e,VS R
EDvo
latilesolid
sredu
ction,
VS a
volatilesolid
sadded,
NRno
trepo
rted,NAno
tapplicable
324 Appl Microbiol Biotechnol (2012) 95:321–329
that codigestion of the combined wastes resulted in highmethane yield as compared to the single waste digestion.Fernandez et al. (2005) study the potential of anaerobicdigestion for the treatment of fats of different originsthrough codigestion with simulated OFMSW. In the study,a pilot plant operating semicontinuously in the mesophilic(37 °C) temperature and HRTof 17 days was employed. Thebiogas and methane yields obtained from the simulatedOFMSWat steady state were 0.8 and 0.5 m3 kg−1 VS added,respectively. On the other hand, no significant differencewas observed in the performance of the anaerobic codiges-tion when animal fat was changed with vegetable fat. Also,the yields of biogas and methane were similar to those foundwith OFMSW, methane content being a bit higher in thepresence of fat. They concluded that both fat from animal orvegetable origin are highly degradable (94 % for animal fatand 97 % for vegetable fat) during codigestion withOFMSW. Therefore, this indicates that anaerobic digestionappears to be a suitable technology for the treatment of suchwastes and obtainment of a renewable energy source. Astudy was performed by Nguyen et al. (2007) to evaluatethe effect of prestage flushing and microaeration in additionto the effect of leachate percolation in methanogenesis stageenhancement in order to develop combined batch anaerobicdigestion systems. The study was conducted in a high solidpilot-scale reactor in two runs. In run 1, prestage flushingand microaeration were carried out to find out their effect interms of enhancing hydrolysis and acidification in ambientcondition. Whereas in run 2, following prestage, new con-dition was provided in order to enhance the start-up ofmethanogenesis stage by adjusting the pH to 6.5 and followedby inoculum addition at mesophilic condition (37 °C). Theresult showed that the application of microaeration achieved75 % biogas conversion and 61 % VS degradation on thehydrolysis and acidification enhancement. Also, the prestageflushing with lesser volume of water (29.3 l/kg TS) was foundto be significant in removing the organic matter from wastebed in preparation for methanogenesis stage. The leachatepercolation during methanogenesis stage demonstrated anenhanced biomethanization when compared to the reactorswithout leachate percolation. The methane yield observedduring the process was 0.26 m3 kg−1 VS added with 75 %process efficiency obtained during the process.
Hartmann and Ahring (2005) investigated the anaerobicdigestion of OFMSW in two thermophilic (55 °C) wet labscale reactor systems. In the first reactor, the OFMSW wascodigested with manure with a subsequent higher concen-tration of OFMSW at HRT of 14–18 days and OLR of 3.3–4 kg VS m−3 day−1. In the second reactor, codigestion ofOFMSW:manure ratio of 50 % (VS/VS) was maintained ascontrol and also the recirculation of 100 % MSW. Resultsshowed that both the codigestion process and the treatmentof 100 % OFMSW with recirculation of process liquid
demonstrated stable operation in spite of fluctuations inthe feed volume. They reported a biogas yield in the rangeof 0.63–0.71 m3 kg−1 VS in both configurations, with VSreduction up to 74 % when treating the 100 % OFMSW.Linke et al. (2006) digested the potato processing wasteanaerobically for biogas production in a CSTR at thermo-phillic condition. They found out that with an increase of theOLR in the range of 0.8–3.4 kg VS m−3 day−1, the biogasyield decreases. In addition, biogas yields with its methanecomposition were obtained to be 0.85 to 0.65 m3 kg−1 VSand 58 to 50 %, respectively. They concluded that specialimportance should be positioned on the reactor performanceat steady state and at OLR that does not result in reactorfailure. Glass et al. (2005) operated a CSTR and an anaer-obic filter (AF) for biogas production from steam-treatedMSW wastewater. The study reported the CSTR productionto be between 0.02 and 0.29 m3 CH4 kg
−1 day−1, while theAF production ranged from 0.04 to 0.47 m3 CH4 kg
−1 day−1.They concluded that the difference in the performance ofboth systems is because the CSTR received wastewatercontaining suspended solids, while the AF received waste-water free from the suspended solids. Sosnowski et al.(2003) studied the anaerobic codigestion of sewage sludgeand OFMSW in a laboratory scale two-phase anaerobicsystem operated in a quasicontinuous mode, with a CSTRas the acidogenic reactor operated at 56 °C and a UASBreactor as the methanogenic reactor operated at 36 °C. Theyreported a higher specific methane yield as 0.024 m3 kg−1
VS added. Also, Fongsatitkul et al. (2010) operated a labo-ratory scale, two-phase, mesophilic anaerobic treatment todetermine the digestibility of OFMSW through codigestionwith varying amounts of return activated sludge (RAS).They found out that increasing the amount of RAS mixedwith OFMSW did not enhance its digestibility, as showedby a decrease in the %VS removal and specific biogasproduction. They concluded that the optimum ratioappeared at 100 % OFMSW (8 % TS) with specific biogasproduction of 0.73 m3 kg−1 VS and a VS removal of about87 % at an HRT of 28 days.
According to Bouallagui et al. (2003), the maximumOLR for the mesophilic anaerobic digestion of fruit andvegetable waste (FVW) in a tubular reactor is 6 % of TSwith a high yield of 0.707 m3 biogas kg−1 VS added for a20-day HRT. These results compared well with that reportedby Hartmann and Ahring (2005). Thus, it can be deducedthat the tubular reactor behaves in a similar way to a CSTRwith high stability and process economy. Further, in a sim-ilar study, Bouallagui et al. (2004) made a comparisonbetween the performances of the tubular anaerobic digestersoperated under thermophilic conditions and those underpsychrophilic and mesophilic conditions. At an OLR of6 % TS (4, 6, 8, and 10 % on dry weight), the yield in thepsychrophilic and mesophilic digesters was almost the same
Appl Microbiol Biotechnol (2012) 95:321–329 325
(Table 1), while the performance of the thermophilic digest-er was higher than that of the mesophilic and psychrophilicdigesters. Also, the highest biogas was obtained in thethermophilic digester at a HRT of 10 days. Hence, theseresults established a phenomenon for OLR selection withthe capability of upgrading the existing mesophilic digestersto the thermophilic range, thereby improving the perfor-mance of the digesters.
Zhang et al. (2007) conducted a batch anaerobic diges-tion test to investigate the biodegradability of FWat an HRTof 10 and 28 days. In the study, the highest methane yield of0.435 m3 kg−1 VS was obtained at the end of the 28-daysdigestion with VS removal of 81 %, which is followed by0.348 m3 kg−1 VS at the end of 10-day digestion. Theseresults indicated that FW was a good alternative substratefor anaerobic digestion because of its high degradability andbiogas yield. In another study, Forster Carneiro et al.(2008b) experimentally study the biomethanization proce-dure of FW in six reactors with three different total solidpercentages (20 %, 25 %, and 30 % TS) and two differentinoculum percentages (20–30 % of mesophilic sludge). Thestudy was designed to select the initial performance param-eters (total solid and inoculum contents) in a lab-scalereactor and later, to validate the optimal parameters in alab-scale batch reactor. The best performance for FW treat-ment and the methane generation was the reactor with 20 %TS and 30 % of inoculum. They observed a methane yieldof 0.49 m3 kg−1 VS added between 20 and 60 days duringthis operation. In addition, the lab-scale batch reactor showsa classical waste removal with high value of methane yieldof 0.22 m3 kg−1 VS added. Finally, they proposed a protocolto improve the start-up phase for dry thermophilic anaerobicdigestion of FW. The study of Bouallagui et al. (2009)observed a maximum OLR of 1.24 kg VS m−3 day−1 oper-ating a thermophilic anaerobic sequencing batch reactor(ASBR) treating FVW with a 15-day HRT. They achieveda high biogas yield of 0.48 m3 kg−1 VS added with 60 %methane content and a 79 % VS reduction. In a similarstudy, Bouallagui et al. (2009) examined the effect of HRTand temperature variations under mesophilic and thermo-philic conditions on the performance of an ASBR treatingabattoir waste water with FVW. They observed a volatilesolid removal between 73 and 86 % and a biogas yield ofabout 0.3–0.73 m3 kg−1 TVS added at OLRs up to 2.56 kgTVS m−3 day−1 in the ASBR codigestion process. Theresults of the digesters' performances showed that the vari-ation in HRT under mesophilic conditions had no significantinfluence on the organic matter removal. However, thebiogas yield at 20 days of HRT was significantly increasedby increasing the temperature from 35 °C to 55 °C. At 55 °C,the HRT of 10 days resulted in overloading and subsequentfailure of the digestion of the AWand the codigestion process.This could possibly be due to the outlet pH and alkalinity
values observed to increase with the increases of the OLR andtemperature, which fail the biogas production.
Alvarez and Liden (2008) experimentally investigatedthe potential of a semicontinuous mesophilic anaerobictreatment of solid slaughterhouse waste, fruit–vegetablewastes, and manure in a codigestion process. Anaerobiccodigestion resulted in methane yields of 0.3 m3 kg−1 VSadded, with methane content between 54 and 56 % at OLRsin the range 0.3–1.3 kg VS m3 day−1. However, the biogasproduction was observed to decrease with an increase inorganic loading and subsequent reduction in the methaneyield indicating organic overload or insufficient bufferingcapacity. They concluded that a combined treatment ofvarious waste types like manure (cattle and swine), solidslaughterhouse wastes (rumen, paunch content, and bloodfrom cattle and swine), and FVW in a mesophilic codiges-tion process establishes the possibility of treating the waste,which cannot be successfully treated separately.
Schober et al. (1999) examined the influence of one-stageand a two-stage continuous bioreactor treating kitchen re-fuse under mesophilic and thermophilic conditions. Theresult of the treatment of this kitchen refuse, containing ahigh amount of easily biodegradable organics, especiallylipids, led to a similar yield of biogas of 0.83 m3 kg−1 VSadded at thermophilic temperatures and 0.80 m3 kg−1 VSadded at mesophilic temperatures. On the other hand, a totalVS reduction of 91 % was achieved with a 7-day HRT in atwo-stage plant using a concentration unit. They concludedfrom main the result that the digestion of MSW should becarried out in a two-stage system with a concentration unitbetween the two stages. By achieving these optimized pro-cess conditions, a turnover of the organic matter of 90 %with low retention time could be accomplished. Parawira etal. (2006) studied the performance of two types of bioreac-tors comparatively treating potato waste leachate. Theyreported that the upflow anaerobic sludge blanket reactor(UASB) demonstrated a stable process with 66 % methanecontent in biogas and a high OLR. This proved superior tothe anaerobic packed-bed reactor (APB) with 59 % methanecontent in the biogas at a lower OLR. The authors found outthat both reactors gave a comparably high performancewhen treating organic matter.
Angelidaki et al. (2006) evaluated how different opera-tional strategies could minimize the process inhibition dueto ammonia accumulation during the anaerobic digestion ofSource-Sorted Organic Fraction of Municipal Solid Waste(SS-OFMSW) in a thermophilic CSTR. At an OLR of11.4 kg VS m−3 day and a 15-day HRT, a stable perfor-mance was observed when SS-OFMSW was diluted withfresh water and when process water was recirculated afterammonia stripping. Methane (CH4) yields from both treat-ments were 0.4 and 0.43 m3 CH4 kg−1 VS added, respec-tively. These results were in accord with the yield reported
326 Appl Microbiol Biotechnol (2012) 95:321–329
by Hartmann and Ahring (2005) during wet digestion of SS-OFMSW at 55 °C with effluent recirculation. Davidsson etal. (2007) conducted a study to investigate the methaneyields from the thermophilic pilot-scale digestion of 17types of domestically SS-OFMSW from households. Theyreported a VS reduction of about 80 % and a methane yieldof 0.3–0.4 Nm3 CH4 kg−1 VS added with a 15-day HRT,corresponding to about 70 % of the potential measuredduring 50-day batch digestion. They concluded that a sort-ing and collection system does not significantly affect theamount of methane produced. Forter-Carneiro et al. (2008a)evaluated the performance of two laboratory-scale reactorstreating OFMSW, SS-OFMSW, and mechanically selectedOFMSW (MS-OFMSW). In the study, discontinuous reac-tors operated at thermophilic temperature and dry digestion(20 % TS) was used. The reactor treating the SS-OFMSWshowed a fast start up beginning within 0–5 days and 20–30 days with a subsequent stabilization phase. AVS reduc-tion of 45 % with a cumulative biogas of 0.120 m3 wasreported in 60 days. Moreover, the MS-OFMSW treatmentindicated a methanogenic phase during the whole period ofexperiment (60 days). They obtained a higher VS removalof 56 % and cumulative biogas of 0.082 m3. These resultsindicated that both digestion treatments were accomplishedand a high level of cumulative methane production wasachieved in less than 60 days.
A study was conducted by Maroun and EL Fadel (2007)in a CSTR to investigate the mesophilic anaerobic digestionof SS-OFMSW. They reported a biogas yield ranging be-tween 0.2 and 0.56 m3 kg−1 VS at an OLR of 2.03 kg VSm−3 day−1. More so, Kim et al. (2006) investigated thedigestibility of FW in a three-stage semicontinuous systemat thermophillic condition. They reported 67 % methanecontent in the biogas at an HRT of 12.4 days. Forster-Carneiro et al. (2008c) conducted a batch experiment todetermine the digestibility of shredded organic fraction ofthe municipals solid waste (SH-OFMSW) and FW separate-ly. Their results indicated that SH-OFMSW is a viablesubstrate for anaerobic digestion with a high VS removalof 74 % and methane yield of 0.05 m3 kg−1 VS added, whilethe FW demonstrates the smallest VS removal (32 %) andhigh methane yield of 0.18 m3 kg−1 VS added. On the otherhand, the OFMSW indicated the highest VS removal(79.5 %) and achieved a methane yield of 0.08 m3 kg−1
VS added. Therefore, they concluded that the nature oforganic substrate has a significant effect on the biodegrada-tion process and methane yield. Also, pretreatment of wasteis not necessary for OFMSW. In another study, Forster-Carneiro et al. (2007) evaluated the effect of different inoc-ulum sources on the performance of laboratory scale reac-tors treating separately collected organic fraction ofmunicipal solid waste (SC-OFMSW). The experimentalconditions selected were: 25 % of inoculums and 30 % of
total solids operated under single phase thermophilic (55 °C)temperature. Results showed that the highest methane yieldwas obtained for sludge inoculums reactor, followed byswine/sludge inoculums reactor, and swine inoculums reactor,with values of 0.29, 0.27, and 0.18 m3 kg−1 VS added,respectively. However, a lower yield of methane was obtainedfor the reactor treating restaurant waste digested with ricehulls, followed by corn silage, and then cattle waste withvalues of 0.11, 0.22, and 0.03 m3 kg−1 VS added, respectively.They concluded that sludge is the best inoculum for thethermophilic anaerobic digestion of SC-OFMSW at dry con-dition (30%TS) achieving 44 % and 43 % COD and VSremoval, respectively.
Sharma et al. (2000) investigated the applicability of aplug flow reactor (PFR) to develop an effective treatment ofsemisolid waste mixed with sewage sludge. Operating underthe mesophilic conditions at 33.7 days HRT, 71 % of VSdestruction was reported with a methane yield of0.7 m3 kg−1 VS added which was equivalent to 1.05 m3
biogas kg−1 VS added. However, at a short HRT of22.5 days, the methane yield did not show any decrease;thus, it can be operated with a short HRT, thereby reducingreactor volume and cost. Consequently, Lastella et al. (2002)investigated the effect of using different bacteria inoculumson the anaerobic treatment of semisolid organic waste avail-able from the ortho fruit market in a PFR under mesophilicconditions. They obtained 68 % methane content in thebiogas and a VS reduction of 72 %. These results weresimilar to that reported by Sharma et al. (2000) during thetreatment of semisolid waste at 37 °C. In another study,Bolzonella et al. (2006) investigated the biogas yield andprocess performance of two full-scale reactors for the treat-ment of differently sorted municipal organic wastes. Theyreported methane yield of 0.4 m3 kg−1 VS added for thereactor treating SS-OFMSW operated under a temperatureof 36.7 °C at HRT of 40–60 days. While the reactor treatingmixed materials consisting of gray wastes, mechanically sortedorganic fraction of municipal solid waste (MS-OFMSW), andsludge showed a methane yield of 0.13 m3 kg−1 VS addedmaintained at a temperature of 38.6 °C at HRT of 50–70 days.They concluded that the strategy of waste collection affects thecharacteristics of the organic waste, hence, affecting the reactoryield even under similar operational conditions. Zupancic et al.(2008) investigated the applicability a full-scale experiment onthe codigestion of organic waste from domestic refuse andmunicipal sludge. In the experiment, the OLR of the digestertreating municipal sludge at HRT of 20 days was raised by25 % to 1 kg VS m−3 day−1 by the addition of organic waste. Itwas observed from the experiment that the biogas productionincreases by 80 % with an increased yield from 0.39 m3 kg−1
VS added before the experiment to 0.6 m3 kg−1 VS added,peaking at 0.89 m3 kg−1 VS added. They concluded that theexperiment achieved high degradation efficiency with virtually
Appl Microbiol Biotechnol (2012) 95:321–329 327
all the organic waste degraded. They recommend the applica-tion of such practice as it will assist in handling organic wastein the future.
Anaerobic digestions of organic solid wastes studiedhave shown to be a renewable energy source that can gen-erate biogas with high methane content. Most of the studieson the anaerobic digestion of solid wastes were conductedon different types of anaerobic reactors at various ranges ofoperating parameters such as temperature, OLR, and HRT.The effect of these parameters on process performance isvery important. The information originating from the litera-ture can be used to draw the following conclusions:
– Anaerobic digestion of municipal garbage showed ahigh performance in the CSTR and two-stage bioreac-tors than batch and ASBR with a methane yield in therange of 0.1–0.7 m3 kg−1 VS added and a VS destruc-tion >80 % with HRT ranging from 7 to 25 days.
– Conventional batch, single-stage, and two-stage anaer-obic digestion processes have been employed to pro-duce biogas from different solid types of substrates suchas municipal solid waste, FVW, FW, etc. The two-phasesystems have shown good stability and optimum biogasproduction. Therefore, more attention should be direct-ed towards the utilization of a two-phase system foroptimum bioenergy recovery. However, the operationof the single-phase in the treatment of solid wastes tobiogas in the rural areas is another alternative for re-newable energy production, especially for developingcountries as well as for the developed countries.
Acknowledgments The authors would like to thank Universiti PutraMalaysia for the financial assistance and facilities, and the NationalFeedlot Corporation for support.
References
Alvarez R, Liden G (2008) Semi-continuous co-digestion of solidslaughter house waste, manure, and fruit and vegetable waste.Renew Energy 33:726–734
Angelidaki I, Cui J, Chen X, Kaparaju P (2006) Operational strategiesfor thermophilic anaerobic digestion of organic fraction of mu-nicipal solid waste in continuously stirred tank reactors. EnvironTechnol 27:855–861
Bolzonella D, Pavan P, Mace S, Cecchi F (2006) Dry anaerobicdigestion of differently sorted organic municipal waste: a full-scale experience. Water Sci Technol 53:23–32
Bouallagui H, Ben Cheikh R, Marouani L, Hamdi M (2003) Meso-philic biogas production from fruit and vegetable waste in atubular digester. Biores Technol 86:85–89
Bouallagui H, Haouari O, Touhami Y, Cheikh RB, Marouani L, HamdiM (2004) Effect of temperature on the performance of an anaer-obic tubular reactor treating fruit and vegetable waste. Proc Bio-chem 39:2143–2148
Bouallagui H, Touhami Y, Cheikh RB, Hamdi M (2005) Bioreactorperformance in anaerobic digestion of fruit and vegetable waste.Proc Biochem 40:989–995
Bouallagui H, Rachdi B, Gannoun H, Hamdi M (2009) Mesophilic andthermophilic anaerobic co-digestion of abattoir wastewater andfruit and vegetable waste in anaerobic sequencing batch reactors.Biodeg 20:401–409
Braber K (1995) Anaerobic digestion of municipal solid waste: amodern waste disposal option on the verge of breakthrough. BioBioener 9:365
Davidsson A, Gruvberger C, Christensen TH, Hansen TL, Jansen JL(2007) Methane yield in source sorted organic fraction of munic-ipal solid waste. Waste Manag 27:406–414
De Baere L (2000) Anaerobic digestion of solid waste: state of the art.Water Sci Technol 41:283–290
Elango D, Pulikesi M, Baskaralingam P, Ramamurthi V, Sivanesan S(2007) Production of biogas from municipal solid waste withdomestic sewage. J Hazard Mater 141:301–304
Fernandez A, Sanchez A, Font X (2005) Anaerobic co-digestion of asimulated organic fraction of municipal solid wastes and fats ofanimal and vegetable origin. J Biochem Eng 26:22–28
Fernandez J, Perez M, Romero LI (2008) Effect of substrate concen-tration on dry mesophilic anaerobic digestion of organic fractionof municipal solid waste (OFMSW). Biores Technol 99:6075–6080
Fernandez J, Perez M, Romero LI (2010) Kinetics of mesophilicanaerobic digestion of the organic fraction of municipal solidwaste: influence of initial total solid concentration. Biores Tech-nol 101:6322–6328
Fongsatitkul P, Elefsiniotis P, Wareham DG (2010) Effect of mixtureratio, solids concentration and hydraulic retention time on theanaerobic digestion of organic fraction of municipal solid waste.Waste Manag Res 28:811–817
Forster-Carneiro T, Perez M, Romero LI, Sahes D (2007) Dry thermo-philic anaerobic digestion of organic fraction of municipal solidwaste: focussing on the inoculums sources. Biores Technol98:3195–3203
Forster-Carneiro T, Perez M, Romero LI (2008a) Anaerobic digestionof municipal solid wastes: dry thermophilic performance. BioresTechnol 99:8180–8184
Forster-Carneiro T, Perez M, Romero LI (2008b) Influence of totalsolids and inoculum contents on performance of anaerobic reac-tors treating food waste. Biores Technol 99:6994–7002
Forster-Carneiro T, Perez M, Romero LI (2008c) Thermophilic anaer-obic digestion of source-sorted organic fraction of municipal solidwaste. Biores Technol 99:6763–6770
Glass CC, Evans MN, Chirwa BD (2005) Biogas production fromsteam-treated municipal solid waste wastewater. Environ EngSci 22:510
Guendouz J, Buffiere P, Cacho J, Carrere M, Delgenes JP (2010) Dryanaerobic digestion in batch mode: design and operation of alaboratory-scale, completely mixed reactor. Waste Manag30:1768–1771
Gunaseelan VN (1997) Anaerobic digestion of biomass for methaneproduction: a review. Bio Bioener 13:83–114
Hartmann H, Ahring BK (2005) Anaerobic digestion of organic frac-tion of municipal solid waste: influence of co-digestion withmanure. Water Res 39:1543–1552
Igoni AH, Ayotamuno MJ, Eze CL, Ogaji SOT, Probert SD (2008)Designs of anaerobic digesters for producing biogas from munic-ipal solid-waste. Appl Ener 85:430–438
IPCC (1996) Intergovernmental panel on climate change. http:/www.ipcc-nggip-.org.jp. Accessed on 25th August 2011
IPCC (2007) Intergovernmental panel on climate change. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf.Accessed 25 August 2011
328 Appl Microbiol Biotechnol (2012) 95:321–329
Kiely G, Tayfur G, Dolan C, Tanji K (1997) Physical and mathematicalmodelling of anaerobic digestion of organic wastes. Water Res31:534
Kim JK, Oh BR, Chun YN, Kim SW (2006) Effect of temperature andhydraulic retention time on anaerobic digestion of food waste. JBiosci Bioeng 102:328–332
Lastella G, Testa C, Cornacchia G, Notornicola M, Voltasio F, SharmaVK (2002) Anaerobic digestion of semi-solid waste: biogas pro-duction and its purification. Ener Conver Manag 43:63–75
Linke B (2006) Kinetic study of thermophilic anaerobic digestion ofsolid wastes from potato processing. Bio Bioener 30:892
Lopez TM, Espinosa LMC (2008) Effect of alkaline pretreatment onanaerobic digestion of solid wastes. Waste Manag 28:2229–2234
Macias-Coral M, Samani Z, Hanson A, Smith G, Funk P, Yu H,Longworth J (2008) Anaerobic digestion of municipal solid wasteand the effect of co-digestion with dairy cow manure. BioresTechnol 99:8288–8293
Maroun R, EL Fadel M (2007) Start-up of anaerobic digestion ofsource-sorted organic municipal solid waste in the absence ofclassical inocula. Environ Sci Technol 41:6808–6814
Nguyen PHL, Kuruparan P, Visvanathan C (2007) Anaerobic digestionof municipal solid waste as a treatment prior to landfill. BioresTechnol 98:380–387
Omar R, Harun RM, Mohd Ghazi TI, Wan Azlina WAKG, Idris A,Yunus R (2008) Anaerobic treatment of cattle manure for biogasproduction. In: Proceedings Philadelphia, Annual meeting ofAmerican Institute of Chemical Engineers, 2008, Philadelphia,USA. Pg. 1-10
Ounnar A, Benhabyles L, Igoud S (2012) Energetic Valorization ofbiomethane produced from cow-dung. Procedia Eng 33:330–334
Parawira W, Murto M, Zvauya R, Mattiasson B (2004) Anaerobicbatch digestion of solid potato waste alone and in combinationwith sugar beet leaves. Renew Ener 29:1811–1823
Parawira W, Murto M, Zvauya R, Mattiasson B (2006) Comparativeperformance of a UASB reactor and an anaerobic packed-bedreactor when treating potato waste leachate. Renew Ener31:893–903
Rao M, Singh S (2004) Bioenergy conversion studies of organicfraction of MSW: kinetic studies and gas yield-organic loadingrelationships for process optimisation. Biores Technol 95:173–185
Rao MS, Singh SP, Singh AK, Sodha MS (2000) Bioenergy conver-sion studies of the organic fraction of MSW: assessment ofultimate bioenergy production potential of municipal garbage.Appl Ener 66:75–78
Schober G, Schaefer J, Schmid-Staiger U, Troesch W (1999) One andtwo-stage digestion of solid organic waste. Water Res 33:854–860
Sharma VK, Testa C, Lastella G, Cornacchia G, Comparat MP (2000)Inclined plug flow type reactor for anaerobic digestion of semi-solid waste. Appl Ener 65:173–185
Sosnowski P, Wieczorek A, Ledakowicz S (2003) Anaerobic co-digestion of sewage sludge and organic fraction of municipalsolid waste. Adv Environ Res 7:609–616
Stroot PG, McMahon KD, Mackie RI, Raskin L (2001) Anaerobiccodigestion of municipal solid waste and biosolids under variousmixing conditions—I. digester performance. Water Res 35:1804–1816
Vandavivere P, De Baere L, Verstraete W (2002) Types of anaerobicdigesters for solid wastes. In: Mata-Alvarez J (ed) Biomethaniza-tion of the organic fraction of municipal solid wastes. IWA,Barcelona
Yu HW, Samini Z, Hanson A, Smith G (2002) Energy recovery fromgrass using two-phase anaerobic digestion. Waste Manage 22:1–5
Zhang R, El-Mashad HM, Hartmann K, Wang F, Liu G, Choate C,Gamble P (2007) Characterization of food waste as feedstock foranaerobic digestion. Biores Technol 98:929
Zsigraiova Z, Tavare G, Semiao V (2009) Integrated waste-to-energyconversion and waste transportation within island communities.Ener 34:623–635
Zupancic GD, Uranjek-Zevart N, Ros M (2008) Full-scale anaerobicco-digestion of organic waste and municipal sludge. BiomassBioener 32:162–167
Appl Microbiol Biotechnol (2012) 95:321–329 329
