Fuel gas enhancement by controlled landfilling of municipal solid waste

Abstract

The controllable processing options available for maximum and accelerated fuel gas production from municipal solid waste (MSW) were studied in the laboratory in “controlled” landfill test cells. Fuel gas production was enhanced substantially compared to conventional “uncontrolled” sanitary landfills. Up to 0.142 m 3 CH 4/dry kg MSW (4600 ft 3 CH 4/dry ton) was obtained in just 3 months under the simulated landfill conditions, equivalent to a conversion of more than 50% of the biodegradable MSW fraction to fuel gas. Twenty-six controlled landfill experiments were performed in up to 200-litre (55 gallon) capacity test cells for periods of up to 410 days. Compaction to 712 kg/m 3 (1200 pounds/cubic yard) was used in all tests. Of the enhancement parameters investigated, the following significantly increased the fuel gas yield and production rate: (1) increasing the moisture content of the MSW; (2) controlling the pH with CaCO, buffer; (3) increasing the population of anaerobic microorganisms; (4) increasing the nutrients (mainly nitrogen and phosphorus); and (5) increasing overall distribution of the materials added throughout the MSW. Digested sewage effluent supplied the nutrients, the inoculum of microorganisms, and the moisture. Both static and leachate recirculation modes were also studied; recycle resulted in slightly higher fuel gas yields. Further, experiments were run at compactions from 593 to 949 kg/m 3 (1000 to 1600 pounds/cubic yard); percent MSW conversions to fuel gas were constant, but higher fuel gas production per unit volume was observed with increasing compaction.