Use of seasonal parameters and their effects on FOD landfill gas modeling

Temporal and spatial variations in landfill gas generations and emissions have been observed and reported by others. Real-time gas data between 2008 and 2014 from a municipal landfill located in a cold, semi-arid climate were consolidated to fit a linear-interpolated form of LandGEM. Seasonal variations in gas collection were observed in the landfill. LandGEM's default decay rate k was not applicable for this Canadian landfill due to significant overestimation (32.2% error). Optimal seasonal k and L_o collection parameters had 8.1% error compared to field data, compared to 8.3% error using optimal annual parameters. The optimal k_winter was 0.0118 year^-1 and the k_summer was 0.0141 year^-1 (14.7% difference), with a corresponding L_o of 100.0 m³/Mg which changed negligibly between the sets. Three pseudo-second order iterative methods were considered, and evaluated using RSS and generation parameters in the literature. A simple application study was conducted using LFGcost-Web, and found the increased precision of seasonal k's resulted in negligible differences with annual optimized k. The default parameters overestimated the net present worth by 12-155% for three of the four common LFG energy projects.