YOLO COUNTY CONTROLLED LANDFILL PROJECT STATUS AFTER 12 YEARS OF OPERATION

摘要

An advanced landfill bioreactor approach termed "controlled landfilling" has been under investigation and development at the Central Landfill, in Yolo County, California since startup of operations in 1994. Important goals include generation and capture of renewable methane energy to full potential, and substantial early waste volume reduction, with associated potentials for landfill life extension and more capacity. Other goals include earlier waste stabilization and minimization of landfill methane greenhouse gas emissions. Two test cells have operated since 1994 at a scale of 9,000 tons. Scaled-up operations began in 2001 in larger cells containing a total of over 200,000 tons of waste. For anaerobic operation (3 cells total), methane generation and waste stabilization have been accelerated through managed additions of supplemental water and leachate. A fourth control cell without supplemental liquid has served as a control. Methane capture has been maximized, with methane greenhouse emissions minimized, by surface geomembrane, with cells operated at slight vacuum to conduct gas to collection. Cells have been intensively instrumented to determine performance. For initial tests, the first-order rate constant for methanogenesis has been over 0.4 year~(-1), over fivefold "normal" for a waste mass of this size. Corresponding to solids' reduction to gas, there has been rapid waste volume reduction. In the first pilot cells, slow and controllable liquid additions have been successful in achieving good moisture distribution as well as rapid waste decomposition. Scaled-up anaerobic bioreactors totaling over 200,000 tons waste in place are in initial monitoring. Details, and results obtained since startup, are presented below.