(729b) Investigation of Woody Biomass and Solid Residue Generated from Anaerobic Digestion and Their Allocation to Potential Energy Generation

In this work, a two-stage municipal solid wastes (MSWs) disposal process has been proposed and its feasibility study has been carried out. At first stage, anaerobic digestion of municipal solid waste, such as grass, leaves and animal manure, was conducted by mixing with anaerobic sludge. Cumulative biogas yield of grass and chicken manure through high-solid co-digestion was 373 mL/g volatile solid (VS) with initial total solid (TS) 20wt% at the temperature of 35°C within 40 days. After digestion, the solid residue was dried until the moisture decreased to 40 wt%. TG analysis results showed that 86wt% of dried residues were volatile solids which could be used as feedstock for gasification. At second stage, the dried solid residue was co-gasified with woody biomass for syngas generation in a fixed-bed downdraft gasifier. Co-gasification of woody biomass and sewage sludge has already been done in our preliminary study. The experimental results showed that 20 wt. % dried sewage sludge in the feedstock was effectively gasified to generate producer gas comprising over 30 vol. % of syngas with an average lower heating value of 4.5 MJ/Nm³. Parameter studies were performed on the basis of optimizing syngas generation of this two-stage process. These included the effects of mixing ratio, heavy metal content and moisture content on the gasification performance. This two-stage process has also been compared with single one stage of anaerobic digestion and gasification process in terms of energy conversing efficiency. Through the two stage process, full utilization of MSWs can be realized to produce biogas and syngas through anaerobic digestion and gasification.