Effect Of Anaerobic Digestion With Cellulase And Hemicellulase Pretreatment On Biodegradable Organic Fraction Of Municipal Solid Waste

Anaerobic digestion is an effective technology for resource utilization to Biodegradable Organic Fraction of Municipal Solid Waste (BOFMSW). For high cellulose content BOFMSW, the stage of hydrolysis and acidification is the rate-limiting step for anaerobic digestion. In this paper, cellulase and hemicellulase were applied to hydrolyze BOFMSW before anaerobic digestion to raise hydrolysis rate, utilization ratio of substrate, biogas yield and shorten digestion period. It was possible to provide the basic data for optimization of anaerobic digestion technology.Firstly, the component of BOFMSW was analyzed. It was found that lignocellulose was the highest material,28.03% and 27.64% respectively for cellulose and xylose.Secondly, when cellulase and hemicellulas were used to hydrolysis BOFMSW the degree of hydrolysis which was influenced by the cellulase and hemicellulase dosage, hydrolysis concentration of substrate (SC), hydrolysis time (HTI), hydrolysis temperature (HTE) and Hydrolyzate pH studied by the method of single factor. The result shown that the optimum condition is cellulase dosage 120U/gVS, substrate concentration 8%(VS concentration), hydrolysis time 24h, hydrolysis temperature 60℃, Hydrolyzate pH5.6, the maximum degree of hydrolysis was 24.2%. Other optimum condition is hemicellulase dosage 200 thousand U/gVS, substrate concentration 10%, hydrolysis time 12h, hydrolysis temperature 50℃, Hydrolyzate pH5.6 the maximum degree of hydrolysis was 37.4%.Thirdly, the effects of substrate to inoculum ratio (SIR) (1:1,1.5:1,2:1,3:1,3.5:1) and digestion concentration(DC) (2%,4%,6%,8%,10% and 12%(VS concentration) respectively on anaerobic digestion were studied by the method of single factor and multi-factor. The single factor method shown that SIR 2.5:1 and DC 6% were the best choice. The multi-factor method shown that the effect order for every factor to produce biogas and methane was DC>SIR.Finally, the effects of pretreatment on the anaerobic digestion of BOFMSW with cellulase and hemicellulase were studied by the method of single factor and multi- factor.The single factor method shown that the optimum condition of strengthening the anaerobic digestion with cellulase pretreatment on BOFMSW was cellulase dosage 120U/gVS, substrate concentration 8%, hydrolysis time 24h, hydrolysis temperature 60℃and Hydrolyzate pH5.6. the optimum condition of strengthening the anaerobic digestion with hemicellulase pretreatment on BOFMSW was hemicellulase dosage 200 thousand U/gVS, substrate concentration 10%, hydrolysis time 12h, hydrolysis temperature 50℃and Hydrolyzate pH5.6.The multi-factor method shown that the effect order for every factor to produce biogas and methane was enzyme dosage,Hydrolyzate pH> hydrolysis temperature,hydrolysis substrate concentration> hydrolysis time,when pretreatment with cellulase; the effect order for every factor to produce biogas and methane was enzyme dosage,Hydrolyzate pH> hydrolysis temperature,hydrolysis time> hydrolysis substrate concentration,when pretreatment with hemicellulase.