Study On The Anaerobic Digestive Performance Of Food Waste And Lignocellulosic Biomass

Lignocellulosic biomass has great potential for producing renewable energy sources such as biomethane through anaerobic digestion.Food waste（FW）has the characteristics of high-water content,high organic matter content and low calorific value.It is a sustainable carbon source for biomass that can be converted into energy.The performance of mono-digestion of lignocellulose biomass and FW could be optimized through pretreatment and combined anaerobic digestion,which can also maximize the conversion of municipal solid waste into energy with good cost-efficiency and environmental friendliness.In this paper,corn cob（CC）was selected as the typical lignocellulosic biomass,and the pretreatment of FW was used to solve the hydrolysis limitation of lignocellulose.The composition and structure changes of lignocellulose during anaerobic digestion were explored.At the same time,considering that there is also a large amount of lignocellulose in the excess sludge,the effects of combined anaerobic digestion of FW and excess sludge on the degradation of lignocellulose in the sludge was also investigated.The experiments also investigated the effects of FW on the anaerobic degradation of free cellulose,hemicellulose,and lignin.The effect of physical pretreatment on the combined anaerobic digestion performance of FW and CC was studied by adding thermal hydrolysis pretreatment corn cob.The main conclusions of the paper are as follows:（1）CC was pretreated with different proportions of FW for one week,and then inoculated sludge was combined with anaerobic digestion.The results show that when the VS ratio of FW to CC is 1:3,the best hydrolysis performance was shown.The efficiency is 19%and the acid production efficiency is 54%.The removal percentages of hemicellulose and cellulose were as high as 80.4%and 79.4%,respectively and the enzyme activity during the FW pretreatment process was also significantly improved.Through the XRD analysis,about 10%of the crystal structure of cellulose was further decomposed,which helped release organic matter from the CC into the solution.During the biogas production phase,acid accumulation caused by the fermentation of FW reduces the activity of methanogens.When the VS ratio of FW to CC is 1:6,the content of food waste in the substrate was lower,while the p H value of the substrate was higher,which shows the best performance in methane production and accumulates methane production potential(401.6 m L CH₄/g·VS_removal).（2）The ratio of 1:6 was selected as the VS ratio of FW to lignocellulose.FW,excess sludge and the single component of lignocellulose were combined for anaerobic digestion.The results showed that the combined anaerobic digestion of FW and excess sludge had the greatest biomethane potential,reaching 407 m L CH₄/g·VS_removal,and the total VS removal rate was 51.79%.The combined anaerobic digestion of FW with free hemicellulose,cellulose and lignin showed the best lignocellulose degradation performance.The hemicellulose degradation percentage was 78.9%and the cellulose degradation percentage was 73.7%.The microbial community and diversity analysis results showed that the addition of FW can effectively promote the accumulation of hydrolytic bacteria,and the free lignocellulose can provide a suitable environment for Firmicutes,thereby improving the biodegradability of lignocellulose.（3）Due to the complex structure of lignocellulosic biomass,it is difficult to biodegrade.This paper used different temperatures to pretreat CC by thermal hydrolysis based on the combined anaerobic digestion of FW and CC.The purpose is to destroy the complex structure inherent in lignocellulosic polymers,so that microorganisms and enzymes can better adsorb and play biodegradation.The results showed that 150℃was the best pretreatment temperature.When the VS ratio of FW to CC was 1:3,the cumulative biogas production reached 4660 m L and the cumulative methane yield was574.7 m L CH₄/g·VS_removal.Among the two ratios of 1:3 and 1:6,the pretreatment at150℃had the greatest promotion effect on the conversion of In-SCOD to SCOD.The3D-EEM data also showed that this temperature is beneficial to the hydrolysis of protein in the biogas slurry.The final degradation of cellulose in the digestive system was 38.9%（1:3）and 28.2%（1:6）higher to the control group.The analysis of microbial community and diversity also showed that 150℃could promote the enrichment of systemic hydrolytic and acid-producing bacteria.The high temperature of 175℃can greatly promote the destruction of lignocellulose structure.However,the excessively high temperature will cause toxic substances in the system,so the overall hydrolysis,acid production and gas production performance were not as good as 150℃.