Inoculum and zeolite synergistic effect on anaerobic digestion of poultry manure
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Inoculum and zeolite synergistic effect on anaerobicdigestion of poultry manureIoannis A. Fotidisa, Panagiotis G. Kougiasab, Ioannis D. Zaganasb, Thomas A. Kotsopoulosb &Gerasimos G. Martzopoulosba Department of Environmental Engineering, Technical University of Denmark, Building 113,Kgs. Lyngby DK-2800, Denmarkb Lab of Alternative Energy Sources in Agriculture, Faculty of Agriculture, AristotleUniversity of Thessaloniki, Thessaloniki 54124, GreeceAccepted author version posted online: 12 Nov 2013.Published online: 09 Dec 2013.
To cite this article: Ioannis A. Fotidis, Panagiotis G. Kougias, Ioannis D. Zaganas, Thomas A. Kotsopoulos & GerasimosG. Martzopoulos (2014) Inoculum and zeolite synergistic effect on anaerobic digestion of poultry manure, EnvironmentalTechnology, 35:10, 1219-1225, DOI: 10.1080/09593330.2013.865083
To link to this article: http://dx.doi.org/10.1080/09593330.2013.865083
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Environmental Technology, 2014Vol. 35, No. 10, 12191225, http://dx.doi.org/10.1080/09593330.2013.865083
Inoculum and zeolite synergistic effect on anaerobic digestion of poultry manure
Ioannis A. Fotidisa, Panagiotis G. Kougiasa,b, Ioannis D. Zaganasb, Thomas A. Kotsopoulosb,and Gerasimos G. Martzopoulosb
aDepartment of Environmental Engineering, Technical University of Denmark, Building 113, Kgs. Lyngby DK-2800, Denmark;bLab of Alternative Energy Sources in Agriculture, Faculty of Agriculture, Aristotle University of Thessaloniki,
Thessaloniki 54124, Greece
(Received 14 July 2013; accepted 7 November 2013 )
Poultry manure is an ammonia-rich substrate due to its high content of proteins and amino acids. Ammonia is the majorinhibitor of anaerobic digestion (AD) process, affecting biogas production and causing great economic losses to the biogasplants. In this study, the effect of different natural zeolite dosages on the mesophilic AD of poultry manure inoculated with anon-acclimatized to ammonia inoculum (dairymanure) was investigated. Additionally, a comparative analysis was performedbetween the data extracted from this study and the results of a previous study, which has been conducted under the sameexperimental conditions but with the use of ammonia acclimatized inoculum (swine manure). At 5 and 10 g zeolite L1, themethane yield of poultry manure was 43.4% and 80.3% higher compared with the experimental set without zeolite addition.However, the ammonia non-acclimatized inoculum was not efficient in digesting poultry manure even in the presence of 10 gzeolite L1, due to low methane production (only 39%) compared with the maximum theoretical yield. Finally, ammoniaacclimatized inoculum and zeolite have demonstrated a possible synergistic effect, which led to a more efficient AD ofpoultry manure. The results of this study could potentially been used by the biogas plant operators to efficiently digest poultrymanure.
Keywords: ammonia toxicity; biogas; poultry manure; zeolite; dairy manure inoculum
1. IntroductionPoultry breeding industries became more intense andmechanised producing vast amount of wastes. Tradi-tional treatment of these wastes (composting, soil appli-cation, etc.) is very difficult due to their unique physic-ochemical characteristics (high chemical oxygen demand(COD) concentration, high ammonia levels, etc.) caus-ing serious problems to the treating facilities. Thus,greenhouse gases (CH4 and CO2) and ammonia emittedfrom the stored poultry manure can degrade the qualityof the atmosphere. Furthermore, direct application of thepoultry manure to the soil as fertilizer (nitrogen and phos-phorus source) could lead to pollution of the surface andground water resources.[3,4] The organic components ofpoultry manure are highly digestible; therefore, anaerobicdigestion (AD) could be considered as the best methodto reduce the organic load of the waste and simulta-neously to produce bioenergy. Additionally, untreatedpoultry manure has higher biogas potential with better pro-duction rate compared with other livestock wastes (e.g.cow and swine manure) as it contains more nutrientsand nitrogen.[6,7] AD is a well-known biological pro-cess mediated by anaerobic protozoa, fungi, bacteria andarchaea, which degrade complex organic material (e.g.
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fats, proteins, carbohydrates) to biogas. However, poul-try manure is a substrate rich in ammonia (ionized+free ammonia) which in high concentrations is the majorinhibitor of biomethanation process. Most of the ammo-nia in poultry manure derives from uric acid, urea andproteins. Free ammonia has been identified as the mosttoxic form of ammonia inhibiting AD process. Thefree ammonia concentration of a substrate is increasingalongside with pH and temperature. It is generallyaccepted that ammonia and free ammonia concentra-tions above 3 g NH+4 NL1 and 0.15 g NH3 NL1,respectively, are inhibiting non-acclimatized to ammoniamethanogenic cultures independently of pH levels andtemperature.[12,13]
Many solutions have been proposed to alleviate ammo-nia toxicity in AD of poultry manure. For example, acommon solution is to dilute the substrate with water,but this method is proven cost-expensive due to largeamount of diluted wastes to be treated. Another commonapproach to degrade poultry manure is to co-digest it withammonia-free substrates. However, ammonia -free sub-strates are either site-specific or seasonable. Therefore, anefficient direct AD method of poultry manure has to bedeveloped.
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A promising solution to counteract the ammonia tox-icity problem is the addition of clay mineral compounds(e.g. andesite, bentonite and natural zeolite). Zeo-lite can entrap the ionized ammonia due to its high cationexchange capacity.Many studies have reported the ben-eficial use of zeolite in AD process under high ammoniaconcentrations.[16,19,20] However, until now, zeolite hasbeen used along with ammonia acclimatized methanogenicinocula (e.g. derived from swine manure-fed digesters).Most of the full-scale digesters operating today use dairymanure as the primary substrate. Dairy manure has lowammonia concentrations compared with swine or poultrymanure, and anaerobic cultures developed in reactors fedwith dairy manure are not acclimatized to high ammo-nia concentrations. Therefore, the effect of zeolite on themesophilic AD of poultry manure inoculated with well-digested dairy manure (non-acclimatized to high ammonialevels) has to be addressed.
The primary aim of this study was to investigate theeffect of different natural zeolite dosages on the mesophilicAD of poultry manure inoculated with a non-acclimatizedto ammonia inoculum, derived from a reactor fed with dairymanure. An additional aim was to perform a comparativeanalysis of the data extracted from this studywith the resultsderived from a previous study, which has been conductedunder the same experimental conditions but with the use ofammonia acclimatized inoculum, derived from a digesterfed with swine manure.
2. Materials and methods2.1. Digestion of poultry manure with dairy inoculum
under different zeolite dosages2.1.1. ZeoliteThe natural zeolite used in the present study was obtainedfrom Xerovouni location of the Avdella-Metaxades Area(Prefecture of Evros, Greece). The chemical andmineralog-ical composition of the zeolite is given in Table 1. Theparticle size of the used zeolite was < 2.0mm.
Table 1. Chemical andmineralogical composition of zeolite.
Chemical composition Mineralogical composition
Oxides % mass Minerals % mass
SiO2 72.96 HEU-type zeolite 54TiO2 0.09 Mica 4Al2O3 11.93 Smectite 6Fe2O3 1.20 Alkali feldspar 8MnO 0.09 Plagioclase 9MgO 1.04 Quartz 8CaO 2.77 Cristobalite 11Na2O 1.29K2O 1.89Loss on ignition 7.61
Table 2. Characteristics of poultry manure used in theexperiment (n = 3, SD).Parameters Poultry
pH 6.85 0.03Total solids (TS), g L1 43.8 0.13Volatile solids (VS), g L1 22.8 0.07Chemical oxygen demand (COD), g L1 28.55 0.72Total Kjeldahl nitrogen (TKN), gNL1 5.45 0.18Total ammonia (NH+4 ), gNL1 4.73 0.12
2.1.2. Poultry manureRaw poultry manure was collected by a poultry farm,located in Neochorouda of Thessaloniki, Greece. Afterarrival to the laboratory, the manure was diluted with dis-tilled water to obtain a total solid concentration of approx-imately 5%. It has been previously documented that thehighest biomethanation of poultry manure can be achievedwhen its concentration is 5%. Table 2 presents thechemical composition of the poultry manure used in theexperiment.
2.1.3. Dairy inoculumThe inoculum used in the batch experiments was obtainedfrom a mesophilic lab-scale continuous stirred tank reactortreating dairymanure (3000mLworking volume; operatingtemperature: 37 1C), and degased prior to usage. Thetotal solids (TS) and volatile solids (VS) of the inoculumused were 15.72 0.58% and 8.69 0.29%, respectively.Moreover, the inoculum had a pH value of 7.82.
2.1.4. Experimental set-upFed-batch reactor tests were performed to investigate thecombined effect of zeolite and dairy inoculum on thebiomethanation of poultry manure. Dairy inoculum wasadded in all fed-batch reactors. The fed-batch reactorsset-up and the zeolite dosage were selected to match theexperimental set-up used by Kougias et al. Thus, in thefed-batch assay setup three different experimental sets wereexamined in triplicate: (a) no zeolite addition, denoted asR0,(b) 5 g zeolite L1, denoted as R5 and (c) 10 g zeolite L1,denoted as R10. Moreover, blank fed-batch reactors con-taining only inoculum and water (i.e. no addition of poultrymanure) were installed to subtract the background CH4 pro-duction of the inoculum from themethane production of thetested experimental sets. Each fed-batch reactor had a totalvolume and working volume of 1000 and 900mL, respec-tively. The reactors were equipped with magnetic stirrersto maintain the substrate homogenous during the diges-tion process. After inoculation, the reactor headspace wasflushed with a N2 gas to ensure anaerobic conditions. Thebatch reactors were placed in an incubator, with controlledtemperature at 36 1C.
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2.2. Comparative analyses of dairy and swineinoculum to digest poultry manure
A comparative analysis of the data extracted from thefed-batch experimental sets of this study with the resultsderived from a previous study, which has been conductedunder exactly the same experimental conditions and zeolitedosages (0, 5 and 10 g zeolite L1) but with the use of anammonia acclimatized inoculum, derived from a digesterfed with swine manure, was performed. Methane yieldand the maximum specific maximum growth rate (max)were used to compare the efficiency of the two aforemen-tioned studies.
2.3. Analytical methodsThe TS, VS, pH, COD, total Kjeldahl nitrogen (TKN),organic nitrogen and ammonia concentrations were deter-mined according to the Standard Methods for Examinationof Water and Wastewater. Volatile fatty acids (VFA)concentrations were measured using a gas chromatograph(HP 5890 series II) equipped with a flame ionizationdetector. The biogas production was measured daily bywater displacement method. Biogas composition (% CH4and % CO2) was also determined daily, using a gas separa-tor containing alkaline solution (3%NaOH). Incubationperiod of the fed-batch reactors is determined as the timeduration of lag and exponential phase.
2.4. CalculationsFree ammonia concentration was calculated as previouslydescribed by Allen et al. The max of the fed-batchmethanogenic cultures was calculated from the slope of thelinear part of the graph of residualmethane production natu-ral logarithm versus time as has been described before.The theoretical methane potential of poultry manure wascalculated considering that 0.35 L of methane is producedper gram COD removal, assuming that the whole incomingCOD is transformed into methane and considering virtuallynegligible the biomass growth and cell maintenance.Students t-test was used for statistically significant differ-ence (p < 0.05) for the specific growth rates and all valuesare the mean of three independent replicates (n = 3) standard deviation (SD). Differences between the methaneyields of the experimental sets comparing the effects ofzeolite and inoculum, and their interaction were examinedusing a two-way analysis of variance (ANOVA). All statis-tical analyses were carried out using the Graphpad PRISMprogram (Graphpad Software, Inc., San Diego, CA).
3. Results and discussion3.1. Digestion of poultry manure with dairy inoculum
under different zeolite dosages3.1.1. Methane production and VS reductionThe accumulatedmethane production of the three fed-batchexperimental sets is presented in Figure 1. The overall
Figure 1. Accumulated methane production in all experimen-tal sets. R0 designates...