The Influence of Waste Composition on the Physico-Biochemical-Hydraulic Characteristics of the Degradation Process of Municipal Solid Waste

Biodegradation of municipal solid waste (MSW) is enhanced in bioreactor landfills via active leachate recirculation. Biogas consisting primarily of methane and carbon dioxide is generated during this process and can be recovered as an energy source. The physical, chemical, geotechnical and hydraulic characteristics of the waste are altered during active biodegradation. However, changes in these characteristics have not been examined closely in the field due to limitations in field measurements. Three laboratory simulators with diameters of 0.3 m and volumes of 42 L were filled with characterized MSW from landfills in Michigan and California to investigate the impact of waste composition on the degradation process. Leachate was recirculated frequently and the progression of MSW biodegradation was monitored via measurements of generation rate of biogas as well as chemical oxygen demand and pH of leachate. The total volume and total weight of the MSW were recorded continuously. The total unit weight, and volumetric water content were calculated. Hydraulic conductivity of the MSW was tested within the same simulators over time. Active biodegradation lasted for approximately 200 days. While significant changes of the physical characteristics were observed during active biodegradation, the changes continued at lower rates even after 800 days. Changes in the physical and biochemical characteristics of the MSW are correlated with the initial waste composition through parameter B that is defined as the percentage of biodegradable constituents in the waste mass.