This report summarizes the results of a laboratory study conducted during 1992-1994 at Argonne National Laboratory. The study examined biogas production and leachate chemistry in parallel anaerobic assays run under either leachate recycle or leachate drainage regimes over a period of 400 days. A standardized synthetic refuse (paper, grass, food) was used in an experimental design which evaluated two elevated moisture contents and two added soils. All assays were conducted in vitro in 125 mL serum bottles. Four recycle/drainage events were completed during the 400 days of this experiment. Sufficient replicates (10 or 20) for each trial were included in the experimental design to permit destructive sampling of assay solids after each recycle/drainage event. Changes in the chemistry of solid, liquid, and gaseous phases were evaluated during the decomposition process. Analyses included major gases (CH{sub 4}, CO{sub 2}, O{sub 2}, N{sub 2}), selected chemical constituents of leachate (Cl-C5 carboxylic acids, total organic carbon, Kjeldahl nitrogen, total phosphorus, iron, zinc, and chloride), leachate pH and conductivity, and selected solids analysis (gravimetric moisture content, volatile solids, total carbon, cellulose, hemicellulose, and lignin).