Bioreactor Study at the Waste Management Outer Loop Landfill

Waste Management Inc. and the USEPA are jointly studying landfill bioreactors through a Cooperative Research and Development Agreement (CRADA) at the Outer Loop landfill in Louisville, KY. The study is evaluating two types of landfill bioreactor technology; aerobic-anaerobic and facultative. The aerobic-anaerobic landfill bioreactor (AALB) process being evaluated involves treating the waste aerobically for a short period followed by anaerobic operation. Duplicate six-acre AALB cells are being studied as they are being filled with waste. The waste density, measured as mass placed over volume consumed, has increased between 14 and 27 percent. Initial densities of 1400 to 1550 lbs/yd³ have been increased to 1840 lbs/yd³ in one case and 1560 lb/yd³ in the other. The facultative landfill bioreactor (FLB) is designed to remove nitrogen from the landfill by external leachate nitrification followed by in situ denitrification of the treated leachate in the landfil. In 2000, a 5-year-old subtitle D landfill was retrofitted to evaluate the FLB process. Since liquid injection began in 2001, the waste density in the FLB has increased by 120 lbs/yd³ to 1620 lbs/yd³. Verification of changes in the municipal solid waste (MSW) has been performed by collecting and analyzing samples of the waste mass over the life of the project. Changes in the cellulose, volatile solids, biochemical methane potential and lignin content of the waste are consistent with the observed increase in density. While the study has at least two more years before the research agreement is complete, this initial work supports predictions that significant gains in airspace are attainable with bioreactor technology. The solid waste industry has projected airspace gains of as much as 30 percent over the life of a bioreactor project.