Research Article Enhanced Solid-State Biogas Production ...downloads.hindawi.com/journals/bmri/2014/350414.pdf · Research Article Enhanced Solid-State Biogas Production from Lignocellulosic

Research ArticleEnhanced Solid-State Biogas Production from LignocellulosicBiomass by Organosolv Pretreatment

Safoora Mirmohamadsadeghi,1 Keikhosro Karimi,1,2 Akram Zamani,1

Hamid Amiri,1 and Ilona Srvri Horvth3

1 Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran2 Industrial Biotechnology Group, Institute of Biotechnology and Bioengineering, Isfahan University of Technology,Isfahan 84156-83111, Iran

3 Swedish Centre for Resource Recovery, University of Boras, 50190 Boras, Sweden

Correspondence should be addressed to Safoora Mirmohamadsadeghi; [email protected]

Received 15 June 2014; Accepted 18 July 2014; Published 5 August 2014

Academic Editor: Meisam Tabatabaei

Copyright 2014 Safoora Mirmohamadsadeghi et al. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Organosolv pretreatment was used to improve solid-state anaerobic digestion (SSAD) for methane production from three differentlignocellulosic substrates (hardwood elm, softwood pine, and agricultural waste rice straw). Pretreatments were conducted at150 and 180C for 30 and 60min using 75% ethanol solution as an organic solvent with addition of sulfuric acid as a catalyst.The statistical analyses showed that pretreatment temperature was the significant factor affecting methane production. Optimumtemperature was 180C for elmwood while it was 150C for both pinewood and rice straw. Maximum methane production was152.7, 93.7, and 71.4 liter per kg carbohydrates (CH), which showed up to 32, 73, and 84% enhancement for rice straw, elmwood, andpinewood, respectively, compared to those from the untreated substrates. An inverse relationship between the total methane yieldand the lignin content of the substrates was observed. Kinetic analysis of the methane production showed that the process followeda first-order model for all untreated and pretreated lignocelluloses.

1. Introduction

Worldwide concerns about the limitations of fossil resources,rising crude oil prices, and greenhouse gas (GHG) emissionshave led researchers to seek alternative clean and renewableenergy sources, for example, biofuels [1]. Lignocellulosicmaterials are abundant and renewable feedstocks that haverecently been considered for the production of biofuels [26].Compared to liquid biofuels, biogas has been shown to havefar better performance with respect to both agricultural landarea efficiency and life cycle assessments [7].

Biogas, produced during anaerobic digestion (AD) pro-cesses, can be used as a versatile source of energy to produceheat and electricity, either separate or combined, and to pro-pel vehicles.Theproduction of biogas offers other advantages,such as controlling organic waste, reducing greenhouse gasemissions, and producing another economically viable fertil-izer [8, 9]. AD processes are classified into liquid anaerobic

digestion (LAD) and solid-state anaerobic digestion (SSAD),based on the solid content [10]. LAD operates at a total solid(TS) content of less than 15%, while SSAD is generally calledfor a TS content of higher than 15% [11]. Smaller specificreactor volume, fewer moving parts, lower energy inputfor heating, easier handling of the end product, and lowerparasitic energy loss are themain advantages of SSAD in com-parison with LAD [1113]. SSAD is specially required withlignocellulosic feedstocks, such as agricultural residues withlow moisture content [11, 14]. However, the anaerobic diges-tion of lignocelluloses is limited by the rate of hydrolysis dueto their recalcitrant structure [15]. Therefore, an additionalpretreatment process is essential to improve their digestibility[15, 16].

Although different factors, for example, the crystallinityof cellulose and the accessible surface area, may play impor-tant roles in the bioconversion of lignocelluloses, the presenceof lignin is apparently the most important factor affecting

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014, Article ID 350414, 6 pageshttp://dx.doi.org/10.1155/2014/350414

2 BioMed Research International

biodegradability [1720]. The lignin-carbohydrate matrixlimits the digestibility of lignocelluloses since lignin is ahydrophobic polymer that forms a cross-linked networkamong the carbohydrates. This network is highly resistantto enzymatic and microbial degradations [6, 21]. Hence, thebiogas production from lignocelluloses can be improved bya delignification process. Removal of lignin by ethanol isamong the most efficient pretreatment techniques in improv-ing bioconversion of lignocelluloses [22, 23]. Furthermore,since lignin is a value added by-product, an additionalunique benefit of organosolv pretreatment is unaltered ligninseparation [23].Therefore, using ethanol as an organosolv forpretreatment prior to the AD process has been reported toimprove the economy of the process by increasing methaneyield and recovery of lignin [24]. To our knowledge, thereis no publication in the literature on utilizing organosolvpretreatment prior to SSAD of lignocelluloses.

The main objective of this study was to improve theperformance of solid-state anaerobic digestion of three dif-ferent types of lignocelluloses, that is, elmwood, pinewood,and rice straw, by applying organosolv pretreatments usingethanol under varying conditions.The effects of the pretreat-ment parameters, that is, temperature and duration time,on the methane yield were determined by solid-state batchanaerobic digestion assays. In addition, the kinetics of thedegradation process was investigated for both untreated andpretreated substrates.

2. Material and Methods

2.1. Feedstocks and Inoculum. Elm, a hardwood, pine, a soft-wood, and rice straw, an agricultural waste, were used assubstrates for biogas production. Elmwood and pinewoodwere obtained from the forest of Isfahan University of Tech-nology (Isfahan, Iran), and rice straw (Sazandegi cultivar,Isfahan, Iran) was sourced from a field in Lenjan Province,Iran. Both elmwood and pinewood were debarked, cut intosmaller pieces, and milled to obtain chips of less than 2 cm.Thewood chips and the rice strawwere partly ball-milled andscreened to achieve powder with particle sizes between 295and 833 m (2080mesh).The screened substrates were thenstored in airtight plastic bags at room temperature until use.

Effluent of a 7000m3mesophilic anaerobic digester (Isfa-han Municipal Sewage Treatment, Isfahan, Iran) was usedas inoculum for the batch digestion assays. Due to its lowTS content, the inoculum was centrifuged at 4500 rpm for30min to obtain the desirable TS content for the SSAD. Thesupernatant was discharged, and the remaining sludge wasmixed to obtain a homogenous inoculum for SSAD. Theinoculum was kept at 37C for one week for stabilization.

2.2. Organosolv Pretreatment. Ethanol as an organic solventtogether with sulfuric acid as catalyst was used for the pre-treatments. A predetermined amount of each feedstock wasmixed with 75% (v/v) aqueous ethanol solution supple-mented with 1% w/w (based on dry mass) sulfuric acid toobtain a solid-to-liquid ratio of 1 : 8 (based on dry mass). Thepretreatments were carried out in a 500mL high-pressurestainless steel batch reactor [25]. After loading the substrate

and the acidic ethanolmixture, the reactorwas heated at a rateof 3C/min to the desired temperature, that is, 150 or 180C,and this temperature was held for 30 or 60min. Then, thereactor was cooled in an ice bath. Afterwards, the pretreatedmaterials were removed, washed three times with 100mLaqueous ethanol (75% v/v, 60C), and left overnight to airdry [24, 26]. The pretreated materials were stored in airtightplastic bags at room temperature until use.

2.3. Solid-State Anaerobic Digestion (SSAD) and Modeling.The untreated and pretreated elmwood, pinewood, and ricestraw (1 g dry mass) were mixed with a predeterminedamount of inoculum and deionized water to achieve afeed-to-inoculum ratio (F/I) (based on volatile solids (VS)content) of 3 and initial TS content of 21%. Sealable 118mLglass reactors were used for the anaerobic digestion assays.Anaerobic conditions were provided by purging the reactorswith nitrogen gas for about 2min, and the reactors werethen incubated in a convection oven atmesophilic conditions(39 1C) for 55 days [27]. Inoculum (without addingany substrate) was evaluated as a blank to determine theinoculums methane production. All digestion assays wererun in duplicate. Gas samples were taken and analyzed forproduced biogas volume and composition in every 3 daysduring the first 9 days of the experimental period and thenin every 5 or 6 days until 55 days.

The kinetics of the anaerobic digestion process was alsoevaluated using a first-order kinetic model (1).The first-orderkinetic model was linearized as shown in (2) [28]:

= , (1)

ln(

) = , (2)

where (day) is time andand

(Lkg1CH) aremethane

yields obtained in 55 days and days, respectively, and is thespecific rate constant.

2.4. Analytical Methods. Total solid (TS) and volatile solid(VS) contents of the feedstocks and inoculumwere measuredby drying the samples at 105C followed by heating the driedresidues at 575C to a constant weight [17].The untreated andpretreated samples were analyzed for lignin and hemicellu-lose contents according to the methods presented by Sluiteret al. [29] and Yang et al. [30], respectively. The cellulosecontent was calculated as the remaining TS, based on anextractive-free basis, assuming that ash, hemicellulose, lignin,and cellulose are the only components of the entire biomass.

Methane and carbon dioxide produced during the anaer-obic digestions were analyzed by a gas chromatograph (Sp-3420A, TCD detector, Beijing Beifen Ruili Analytical Instru-ment Co., China) equipped with a packed column (3mlength and 3mm internal diameter, stainless steel, Porapak Qcolumn, Chrompack, Germany).The carrier gas was nitrogenat a flow rate of 45mL/min. The column, injector, and detec-tor temperatures were 40, 100, and 150C, respectively. Apressure-tight syringe (VICI, Precision Sampling, Inc., USA)with a volume of 250L was used for gas sampling and

BioMed Research International 3

Table 1: Composition analyses of the inoculum as well as the untreated versus pretreated feedstocks.

Samples Pretreatment TS content (%) VS content (%) Total lignin (%) Hemicellulose (%) Cellulose (%)

Inoculum 5.7 2.7 ND ND NDCentrifuged 11.7 5.3 ND ND ND

Elmwood

Untreated 95.5 94.5 26.2 26.3 46.4150C, 0.5 h 95.5 94.1 25.1 23.4 50.0150C, 1 h 95.5 93.8 23.4 21.5 53.3180C, 0.5 h 96.3 94.4 20.4 21.9 55.7180C, 1 h 94.9 93.6 19.1 21.3 58.1

Pinewood


Rice straw


ND = not determined.Sum of acid soluble lignin (ASL) and acid insoluble lignin (AIL) contents.

injection, enabling taking of gas samples at the bioreactorsactual pressure. Excess gas was released through a needleafter each gas sampling to avoid overpressure built-up in thebottles.

All biogas yields were presented at standard conditions.

2.5. Statistical Analysis. Analysis of variance (ANOVA) usingMinitab software v. 15 was performed to compare confidenceintervals and significance between treatments. The factorswere considered significant when the probability ( value)was less than 0.05.

3. Results and Discussion

3.1. Characterization of Inoculum. The inoculum obtainedfrom the industrial biogas plant contained 5.7 and 2.7% TSandVS, respectively (Table 1). In order to achieve aTS contentof 21% in SSAD, the inoculum was centrifuged [31] to reachTS and VS contents of 11.7% and 5.3%, respectively (Table 1).

3.2.TheEffect of Different PretreatmentConditions on the Com-position of Substrates. Elmwood, pinewood, and rice strawwere subjected to organosolv pretreatment using ethanolprior to anaerobic digestion in order to improve the yieldof biogas production.The untreated and pretreated materialswere characterized, according to their TS, VS, lignin, cellu-lose, and hemicellulose contents, and results are summarizedin Table 1.

Total lignin contents of untreated elmwood and pine-wood were 26.2 and 26.8%, respectively, which was muchhigher than that of untreated rice straw (17.1%).

The various components of the materials were differ-ently affected by the pretreatments. Depending on the pre-treatment conditions, the lignin contents were reduced by

427% for elmwood, by 121% for pinewood, and by 2137%for rice straw. Increasing the severity of the pretreatmentgenerally resulted in higher lignin removal. A relativelyhigh portion of straws lignin (37.7%) was removed throughpretreatment at 180C for 60min, resulting in a pretreatedstraw with carbohydrate content of over 77% of TS. On theother hand, the organosolv pretreatment of elmwood andpinewood, at 180C for 60min, resulted in 27% and 21%lignin removal, respectively, with correspondingCH contentsof 72.7% and 72.5% of TS, respectively. In addition todelignification, parts of hemicelluloses were also removeddue to the pretreatments. Higher hemicellulose removal wasobtained in pretreated pinewoods (2840%), compared tothat in elmwood (1119%) or straw (916%).

3.3. Biogas Production. Organosolv pretreatments in fourdifferent conditions were performed on the three differentlignocellulosic materials, and the methane yields of the pre-treated and untreated materials were then measured throughbatch SSAD assays. The accumulated methane productionsobtained during 55 days of digestion from the untreated andpretreated materials are shown in Figure 1.

Methane production yields from all of the substrates weregenerally improved by the pretreatments in all conditions.The highest methane yield of 152.7 Lkg1CH was obtainedfrom rice straw pretreated at 150C for 1 h (Table 2). How-ever increasing the pretreatment temperature resulted in areduced methane yield. This could be due to the inhibitoryproducts which can be formed at high temperature duringthe pretreatment. In contrast, the highest yield of methaneproduction from pretreated elmwood (93.7 Lkg1CH) wasobtained after pretreatment at 180C for 1 h; hence, themethane production from elmwood was improved byincreasing the severity of the pretreatment. However, the


Table 2: The accumulated methane yields obtained after 55 days of anaerobic digestion from untreated and pretreated lignocellulosicsubstrates together with the specific rate constants and the regression coefficients calculated from the first-order kinetic model fitting.

Sample Pretreated conditions CH4 (Lkg1CH) (day1) 2

Elmwood

Untreated 54.2 3.5 0.054 0.975150C, 0.5 h 55.4 9.7 0.063 0.934150C, 1 h 63.6 12.3 0.066 0.914180C, 0.5 h 78.7 0.4 0.062 0.961180C, 1 h 93.7 0.9 0.097 0.937

Pinewood


Rice straw


0

40

80

120

160

0 10 20 30 40 50Time (day)

Accu

mul

ated

CH4

(Lk

g1

CH)

(a)

0

40

80

120

160

0 10 20 30 40 50Time (day)

Accu

mul

ated

CH4

(Lk

g1

CH)

(b)

0

40

80

120

160

0 10 20 30 40 50Time (day)

Accu

mul

ated

CH4

(Lk

g1

CH)

(c)

Figure 1: Accumulatedmethane production fromSSADof untreated and pretreated (a) elmwood, (b) pinewood, and (c) rice straw in differentpretreatment conditions. The symbols represent the untreated substrates (X), the substrates pretreated at 150C for 0.5 h (), at 150C for 1 h(), at 180C for 0.5 h (+), and at 180C for 1 h ().

pretreatment of pinewood at 150C for 0.5 h (the lowestseverity) resulted in a methane yield of 71.4 Lkg1CH, whichshowed 84% improvement compared to the methane yieldfrom untreated pinewood. Although pretreating pinewoodhad a remarkable effect on the yield of methane production

(i.e., improvements of 4584%), the statistical analyses usingmethane yield as response variable showed that neithertemperature nor time, with values of 0.28 and 0.91, respec-tively, had a significant effect on methane yield in the caseof pinewood. In contrast, pretreatment temperature had

BioMed Research International 5

a significant effect on the methane production from elm-wood and rice straw; while being similar to that of pinewood,it was concluded that the effect of pretreatment time onmethane production from elmwood, pinewood, and ricestraw was not significant ( values of 0.14, 0.91, and 0.27,resp.).

Among the untreated samples, the highest methane yield,115.9 Lkg1CH, was obtained from rice straw, which had thelowest lignin content among the substrates utilized in thisstudy. The digestion of untreated elmwood and pinewoodresulted inmethane yields of 54.2 and 38.7 Lkg1CH, respec-tively. The presence of pores in the structure of hard-woods which facilitate microorganisms accessibility mightbe responsible for the higher yield obtained from elmwoodin comparison to that from pinewood [32].

3.4. Methane Production Modeling. The fitting of kineticsdata on the first-order model for all of the substrates isshown in Table 2, as well as the accumulated methane yieldsobtained after 55 days of SSAD. The regression coefficientsdemonstrated that methane production followed the first-order kinetic model (2 > 0.91). At the optimum pretreat-ment conditions for each substrate, that is, 180C and 1 h,150C and 0.5 h, and 150C and 1 h for elmwood, pinewood,and rice straw, the corresponding value was at its maximumlevel, respectively, representing the highest degradation ratefor each investigated substrate.

3.5. Relationship between Total Lignin Content and MethaneYield from Lignocellulosic Materials. The effect of lignin con-tent on final methane yield was investigated by comparingmethane yield as a function of the materials lignin content(Figure 2). In line with a previous study [28], an overallinverse relationship between the lignin content of differentsubstrates and the achieved methane yields was observed.However, the low linear regression coefficient of 0.7 con-firmed that the content of lignin is not the sole key fac-tor affecting methane yield. The contents of cellulose andhemicellulose, the crystallinity of cellulose, and the accessiblesurface area may also play important roles affecting methaneyields [1720]. Therefore, further investigations are requiredto find the specific reason for the observed improvements.

4. Conclusions

Organosolv pretreatment prior to SSAD was an efficientprocess for improvement of methane production from dif-ferent types of lignocellulosic materials; however, its effec-tiveness greatly depended on the type of lignocelluloses. Thepretreatment process was more effective on softwood thanon hardwood or agricultural waste. Moreover, hardwoodneeded more severe conditions to be able to achieve max-imum improvement during the subsequent batch digestionassays. Lignin content was among the most important factorsnegatively affecting the methane production from all of theinvestigated lignocellulosic substrates.

0

50

100

150

10 15 20 25

Tota

l met

hane

yie

ld (L

/kg

CH)

Lignin content (%)

y = 4.7x + 179.6

R2 = 0.7

Figure 2: Relationship between lignin content and total methaneyield from lignocellulosic substrates (untreated and pretreatedelmwood, pinewood, and rice straw).

Conflict of InterestsThe authors declare that there is no conflict of interestsregarding the publication of this paper.

Authors Contribution

All experiments and paper preparation were performed bySafoora Mirmohamadsadeghi. The coauthors supervised theexperiments and helped with paper preparation.

Acknowledgments

Theauthors are grateful for financial support from the RegionVastra Gotaland and the Institute of Biotechnology andBioengineering, Isfahan University of Technology.

References

[1] D. Deublein and A. Steinhauser, Biogas fromWaste and Renew-able Resources: An Introduction, Wiley, 2008.

[2] E. Gnansounou, Production and use of lignocellulosic bio-ethanol in Europe: current situation and perspectives, Biore-source Technology, vol. 101, no. 13, pp. 48424850, 2010.

[3] J. Hromadko, J. Hromadko, P. Miler, V. Honig, and M. Cindr,Technologies in second-generation biofuel production,Chemicke Listy, vol. 104, no. 8, pp. 784790, 2010.

[4] R. E. H. Sims, W. Mabee, J. N. Saddler, and M. Taylor, Anoverview of second generation biofuel technologies, Biore-source Technology, vol. 101, no. 6, pp. 15701580, 2010.

[5] G. Sivakumar, D. R. Vail, J. Xu et al., Bioethanol and biodiesel:Alternative liquid fuels for future generations, Engineering inLife Sciences, vol. 10, no. 1, pp. 818, 2010.

[6] S. Kumar, Hydrothermal processing of biomass for biofuels,Biofuel Research Journal, vol. 2, p. 43, 2014.

[7] P. Borjesson and B. Mattiasson, Biogas as a resource-efficientvehicle fuel, Trends in Biotechnology, vol. 26, no. 1, pp. 713,2008.

[8] G. Taleghani and A. S. Kia, Technical-economical analysis ofthe Saveh biogas power plant, Renewable Energy, vol. 30, no. 3,pp. 441446, 2005.


[9] M. Balat and H. Balat, Biogas as a renewable energy sourceareview, Energy Sources, Part A: Recovery, Utilization and Envi-ronmental Effects, vol. 31, no. 14, pp. 12801293, 2009.

[10] Y. Li, S. Y. Park, and J. Zhu, Solid-state anaerobic digestionfor methane production from organic waste, Renewable andSustainable Energy Reviews, vol. 15, no. 1, pp. 821826, 2011.

[11] D. Brown, J. Shi, and Y. Li, Comparison of solid-state to liquidanaerobic digestion of lignocellulosic feedstocks for biogasproduction, Bioresource Technology, vol. 124, pp. 379386, 2012.

[12] J. Guendouz, P. Buffiere, J. Cacho, M. Carrere, and J. Delgenes,High-solids anaerobic digestion: comparison of three pilotscales, Water Science and Technology, vol. 58, no. 9, pp. 17571763, 2008.

[13] Y.-S. Cheng, Y. Zheng, C. W. Yu, T. M. Dooley, B. M. Jenkins,and J. S. Vandergheynst, Evaluation of high solids alkalinepretreatment of rice straw, Applied Biochemistry and Biotech-nology, vol. 162, no. 6, pp. 17681784, 2010.

[14] R. R. Singhania, A. K. Patel, C. R. Soccol, andA. Pandey, Recentadvances in solid-state fermentation, Biochemical EngineeringJournal, vol. 44, no. 1, pp. 1318, 2009.

[15] M. J. Taherzadeh and K. Karimi, Pretreatment of lignocel-lulosic wastes to improve ethanol and biogas production: areview, International Journal of Molecular Sciences, vol. 9, no.9, pp. 16211651, 2008.

[16] A. Teghammar, K. Karimi, I. Sarvari Horvath, and M. J. Taher-zadeh, Enhanced biogas production from rice straw, triticalestraw and softwood spruce by NMMO pretreatment, Biomassand Bioenergy, vol. 36, pp. 116120, 2012.

[17] V. S. Chang and M. T. Holtzapple, Fundamental factors affect-ing biomass enzymatic reactivity, in Proceedings of the 21st Sym-posium on Biotechnology for Fuels and Chemicals, Springer,2000.

[18] L. Laureano-Perez, F. Teymouri, H. Alizadeh, and B. E. Dale,Understanding factors that limit enzymatic hydrolysis of bio-mass: Characterization of pretreated corn stover, Applied Bio-chemistry and Biotechnology, vol. 124, no. 13, pp. 10811099,2005.

[19] V. P. Puri, Effect of crystallinity and degree of polymerizationof cellulose on enzymatic saccharification, Biotechnology andBioengineering, vol. 26, no. 10, pp. 12191222, 1984.

[20] D. P. Koullas, P. Christakopoulos, D. Kekos, B. J. Macris, andE. G. Koukios, Correlating the effect of pretreatment on theenzymatic hydrolysis of straw, Biotechnology and Bioengineer-ing, vol. 39, no. 1, pp. 113116, 1992.

[21] N. Poornejad, K. Karimi, and T. Behzad, Ionic liquid pretreat-ment of rice straw to enhance saccharification and bioethanolproduction, Journal of Biomass to Biofuel, vol. 2, no. 1, pp. 815,2014.

[22] P. Binod, R. Sindhu, R. R. Singhania et al., Bioethanol produc-tion from rice straw: an overview, Bioresource Technology, vol.101, no. 13, pp. 47674774, 2010.

[23] X. Zhao, K. Cheng, andD. Liu, Organosolv pretreatment of lig-nocellulosic biomass for enzymatic hydrolysis, Applied Micro-biology and Biotechnology, vol. 82, no. 5, pp. 815827, 2009.

[24] P. Obama, G. Ricochon, L. Muniglia, and N. Brosse, Combina-tion of enzymatic hydrolysis and ethanol organosolv pretreat-ments: Effect on lignin structures, delignification yields andcellulose-to-glucose conversion, Bioresource Technology, vol.112, pp. 156163, 2012.

[25] H. Amiri, K. Karimi, and S. Roodpeyma, Production of furansfrom rice straw by single-phase and biphasic systems, Carbo-hydrate Research, vol. 345, no. 15, pp. 21332138, 2010.

[26] H. Amiri, K. Karimi, and H. Zilouei, Organosolv pretreatmentof rice straw for efficient acetone, butanol, and ethanol produc-tion, Bioresource Technology, vol. 152, pp. 450456, 2014.

[27] T. L. Hansen, J. E. Schmidt, I. Angelidaki et al., Method fordetermination of methane potentials of solid organic waste,Waste Management, vol. 24, no. 4, pp. 393400, 2004.

[28] L. N. Liew, J. Shi, and Y. Li, Methane production from solid-state anaerobic digestion of lignocellulosic biomass, Biomass &Bioenergy, vol. 46, pp. 125132, 2012.

[29] A. Sluiter, B. Hames, R. Ruiz et al., Determination of StructuralCarbohydrates and Lignin in Biomass, Laboratory AnalyticalProcedure, 2008.

[30] H. Yang, R. Yan, H. Chen, C. Zheng, D. H. Lee, and D. T. Liang,In-depth investigation of biomass pyrolysis based on threemajor components: Hemicellulose, cellulose and lignin, Energyand Fuels, vol. 20, no. 1, pp. 388393, 2006.

[31] D. Brown and Y. Li, Solid state anaerobic co-digestion of yardwaste and food waste for biogas production, Bioresource Tech-nology, vol. 127, pp. 275280, 2013.

[32] A. Reiterer, G. Sinn, and S. E. Stanzl-Tschegg, Fracture char-acteristics of different wood species under mode I loading per-pendicular to the grain, Materials Science and Engineering A,vol. 332, no. 1-2, pp. 2936, 2002.

Submit your manuscripts athttp://www.hindawi.com

Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation http://www.hindawi.com

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation http://www.hindawi.com Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttp://www.hindawi.com

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research


International Journal of

Microbiology

Documents

Research Article Enhanced Solid-State Biogas Production ...downloads.hindawi.com/journals/bmri/2014/350414.pdf · Research Article Enhanced Solid-State Biogas Production from Lignocellulosic