Abiotic decomposition of municipal solid waste under elevated temperature landfill conditions

Abiotic decomposition of simulated Municipal Solid Waste (MSW) was investigated for thermal reactions that impact landfill gas components such as methane, carbon dioxide, and hydrogen. The gas composition and temperature were monitored as a function of heating rate and time. The tests were conducted at 483 kPa (70 psig), 55 wt% moisture, and 30 to 60 W controlled heat input in the presence of biological inhibitors. The gas composition trends show that for heat inputs higher than 46 W, the CH₄/CO₂ ratio diverges from the initial value of 1.0 to as low as 0.2, correlated to a decrease in CH₄ concentration. Major findings of the study include that the primary gas composition ratio (CH₄/CO₂) starts to reduce from the baseline value of 1.0 as the heating rate is increased from 30 W to 51 W and further declines at significantly higher rates beyond 51 W. The hydrogen evolution was directly proportional to the amount of CH₄ available in the system. Low levels of CH₄ (<25%) correspond to decreased H₂ levels in the system (<5%) whereas injection of CH₄ gas in the system correspond with a renewed H₂ generation The study provides insights into the operational conditions such as available heat and moisture leading to changes in landfill gas ratios.