Study On The Methane Production Of Waste Paper Through Anaerobic Digestion

Waste papers take a considerable proportion in domestic waste,while much waste paper cannot be recycled for papermaking due to the unrecyclability and high recycling cost,which makes these waste paper as a potential feedstock for the production of clean energy.In this study,the anaerobic digestion characteristics of different waste papers and evaluation on the co-digestion of waste papers with sheep manure were investigated,as well as the enhancement of methane production during the solid state anaerobic digestion of waste paper through anaerobic and aerobic pretreatment.To further elucidate the mechanisms of anaerobic digestion of individual lignocellulosic component,the methane production characteristics and interactions of cellulose,hemicellulose and lignin during anaerobic digestion were investigated.Moreover,the functions of chracteristic bacteria and methanoges involved in the anaerobic digestion were analyzed.The main results of this study are as follows:(1)The corrugated board,waste office paper,magazine paper and tissue paper were used as substrates for methane production through anaerobic digestion,it was found that waste papers with high cellulose and low lignin contents possesses higher biomethane potential and biodegradability.The co-digestion of waste paper with sheep manure had synergistic effect on methane yield,which might be related to the balanced carbon to nitrogen ratio and nutrients in co-digestion.The addition of sheep manure to waste paper increased the microbial diversity and richeness.The relative abundance of some characteristic bacteria in the co-digestates were higher than that of mono-digestates,these bacteria were likely correlated with the enhancred methane yield observed from the co-digestions,such as potential ellulose degraders(Clostridium ?,Pseudobacteroides,etc.),sugar fermenters(Levilinea,Treponema,etc.)and methanogens(Methano spirillum,Methanothrix,etc.).(2)The pretreatment on waste papers by straw-decomposing inculant,sheep manure and digestate effluent enhanced methane yield more than 20%in comparison with the untreated.Bacillus sourced from straw-decomposing inculant,Ruminococcus sourced from sheep manure,Ruminococcaceae Incertae Sedis and Clostridium sensu stricto 1 existed in the sheep manure and digestate effluent,VadinBC27?Fastidiosipila and Petrimonas sourced from digestate effluent,and Pseudomonas and Acinetobacter sourced from all of the three pretreatment inoculant,these bacteria played vital roles in the pretreatment of waste papers.(3)The biomethane potential of cellulose was higher than that of hemicelluloses,while lignin canot be digested during anaerobic digestion.Hemicelluloses were hydrolyzed more quickly than cellulose,and the concentration of volatile fatty acids in the fermentation liquor of hemicelluloses were higher,which resulted in a lower pH and more severe inhibition on methane production of hemicelluloses than those of cellulose.Compared to mono-digestions,the co-digestion of cellulose and hemicellulose increased the methane yield and biodegradability.Therefore,the co-digestion of cellulose-rich substrates with hemicelluloses-rich substrates should be a considerable strategy to enhance anaerobic digestion performance.The inhibition of lignin on the methane production of cellulose was stronger than that of hemicelluloses.Some functional bacteria,such as Clostridium sensu stricto,Cloacibacillus and Christensenella showed higher abundance in the mono-digestate of cellulose and its co-digestates.Sugar-fermenting Saccharofermentans and Levilinea played important roles in the utilization of various sugars hydrolyzed from hemicelluloses.Methanogens including Methanospirillum and acetotrophic Methanothrix mainly contributed to the methane production of cellulose.Potential aciduric Methanobrevibacter,Methanomassiliicoccus,Methanobacterium and Methanoculleus were responsible for the bio-methanation from hemicelluloses.These characteristic microorganisms are worth exploiting for the bioaugmentation in the anaerobic digestion of lignocellulosic biomass.