Implications of municipal solid waste co-disposal experiments on biodegradation and biochemical compatibility

The objective of this study was to evaluate waste biodegradation and biochemical compatibility for different waste co-disposed with municipal solid waste (MSW). Laboratory-scale reactors were operated with MSW co-disposed with special solid waste, liquid waste, or sludge waste. Early and aggressive addition of liquid wastes during reactor startup did not stimulate anaerobic decomposition of fresh MSW. The majority of the liquid waste reactors were acid stuck and had leachate pH < 6 and chemical oxygen demand in the range of 50,000 mg-O₂/L. The majority of liquid wastes in this study were not observed to be effective anaerobic inoculums and would not be recommended as the sole moisture source for bioreactor landfills. Enhanced early methane production was observed in the MSW reactors co-disposed with sludge (anaerobic and industrial) relative to the landfill leachate control reactors and all other waste combinations evaluated. Methane generation was observed in reactors operated with foundry waste or gypsum board co-disposed with MSW. Despite biochemical methane potential (BMP) results that indicated methane generation would be inhibited with these two waste streams, co-disposing with MSW did not completely inhibit anaerobic degradation. The BMP assays provided methane yield under ideal conditions, but did not capture other benefits of co-disposal (e.g., impacts of moisture addition). A potential co-disposal waste source should not be ruled out by BMP results alone.