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93 Improvement of Biogas Production from Lignocellulosic Materials by Alkali Pretreatment Peyman Salehian p salehina@ce iut ac ir Date of submission Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language PersianSupervisor Keikhosro Karimi karimi@cc iut ac ir Hamid Zilouei hzilouei@cc iut ac irAbstractAlkali pretreatment is among the most promising methods for pretreatment It could modify the structure oflignocellulosic materials by increasing the surface area reducing the crystallinity of cellulose andhemicellulose and lignin removal thus significantly increase the degradability of lignocelluloses However the efficiency of alkali pretreatment highly depends on the process conditions i e temperature concentration and the treatment time as well as the inherent characteristics of the lignocellulose used Theobjective of this research was to develop an alkali pretreatment process prior to anaerobic digestion AD ofcattle manure and pine wood to improve the methane productivity Laboratory scale experiments werecarried out in completely batch bioreactors 118 ml capacity The mesophilic anaerobic digestions wereperformed and produced gases were analyzed by gas chromatography At the first step alkaline treatmentwith Ca OH 2 was used for improvement of biogas production from cattle manure Effects of temperature 20 C and 60 C time 0 2 and 12 h and pH 9 10 11 and 12 in liming pretreatment of the manure onbiogas production were investigated The results showed that alkaline treatment at 20 C was not effective onbiogas production The manure treated at the elevated temperature 60 C produced more methane than theuntreated manure The biogas production was increased with increase in duration time of treatment and pH The maximum amount of biogas produced was observed from the manure treated for 12 h at pH 12 whichwas 225 4 ml CH4 g VS This was more than 76 higher yield of biogas than that of untreated manure Theanalysis of the treated manure showed that the alkaline treatment eliminated 22 7 of the total lignin whichcould be the reason for improvement of digestibility of the manure and increase in biogas production yield At the second steps alkaline pretreatment with NaOH was used to improve biogas production from softwoodpine The pretreatments were carried out at different temperatures 0 and 100 C with 8 0 w w NaOHsolution for different periods of time 10 30 60 min The pretreated materials were then anaerobicallydigested to biogas Clear positive effects of the pretreatments on the yield of methane were observed Thebest improvement was achieved at 100oC when 8 NaOH for 10 min was used for the pretreatment whichresulted in 181 2 improvement in the yield of methane production In addition treatment with NaOH for 60min at 0oC resulted in 118 6 improvement in the methane yield compared to that of the untreated material The pretreatment resulted in significant reducing the crystallinity of cellulose and lignin removal andswelling the structure of wood which might be responsible for improved biogas production At the thirdsteps pretreatment of different parts of pine wood i e stem trunk branches bark and cones were studiedby 8 0 w w NaOH under the conditions in which the best improvement was achieved in the second steps 100oC for 10 min and 0oC for 60 min The effects of pretreatment on composition and biogas production ofthe wood were investigated Pretreatment of different parts of the tree were studied at the same temperature NaOH concentration and solid loading The results showed that the pretreatment can significantly improvethe yield and productivity of the biogas however the optimum condition for each part is different and theefficiency of the treatment highly depends on the composition of the different parts Key words Alkali pretreatment biogas cow manure pine wood

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فرآوري قليايي مواد ليگنوسلولزي به منظور بهبود توليد بيوگاز

پيش فرآوري قليايي , چوب كاج , كود گاوي