Anaerobic Bioconversion of Municipal Solid Wastes: Effects of Total Solids Levels on Microbial Numbers and Hydrolytic Enzyme Activities

The anaerobic bioconversion of municipal solid wastes (MSW) produces both a valuable fuel product (methane) and a residue useful as a soil amendment. The application of high-solids fermentation technology offers improved economics over the more traditional low-solids fermentation systems. An important benefit of the high-solids process is the reduction in process water, which results in smaller fermentation reactors, and thus lower capital and operating costs. However, the anaerobic bioconversion process appears to be more efficient at high-solids as compared to low-solids levels. To understand the effects of solids levels on the anaerobic bioconversion process more thoroughly, representative high-solids and low-solids anaerobic reactor systems processing identical MSW feedstocks are compared with respect to fermentation performance, total microbial cell number, and important hydrolytic enzyme activities.