Landfill gas is a source of biomass energy that is used primarily to generate electric power. Biomass is converted to gas in landfills as the organic material is exposed to moisture and bacterial /fungal decomposition. The organic material is converted to approximately 60 percent CO2 and 40 percent on a mass basis. Trace levels of hydrocarbons, sulfur-containing compounds and chlorinated compounds are also produced. Landfill gas is either flared or used to generate electricity. Other uses of landfill gas include methanol and hydrogen production.
Methanol has not been produced from biomass for use in California. A landfill gas to methanol project was planned for construction in Southern California but permitting issues prevented the project from going forwards (Wuebben).
Hydrogen Burner Technology (HBT) has a contract with the SCAQMD to develop a hydrogen production system based on the partial oxidation of LFG. Several landfill sites have been considered as possible sites for hydrogen production. The interest in hydrogen production indicates that alternatives to flaring and power generation are of interest to landfill operators.
Landfill gas is continuously exiting from the landfill either as uncontrolled losses, flared gas, or combusted gas for power generation. When LFG is converted to methanol, one of these pathways is interrupted. The question of marginal emissions is important for LFG as the alternative uses of LFG vary considerably. LFG is generally not vented in California and even in rare instances where it might be vented, crediting methanol production with these emission reductions does not reflect the marginal impact of the methanol production facility. The emissions impacts of producing using LFG from flared gas and IC engines are discussed below. Emission levels are quantified in Section 4.
3.7.1 Flared LFG
Flaring LFG results in emissions of NMOG, CH4, NOx, CO, traces of PM, and CO2. Since the gas is primarily CH4 and CO2, NMOG emissions are low. Flares operate at relatively low temperatures so NOx emissions are also relatively low. LFG is derived from biomass. The biomass consists of paper, food waste, wood waste, and other organic materials. The carbon is derived from CO2 that was recently removed from the atmosphere. Therefore, flared LFG has zero net CO2 associated with it. This CO2 is counted as biomass CO2 in this study.
3.7.2 Electric Power from LFG
Many landfills generate electric power from LFG. LFG is combusted either in IC engines or gas turbines. Producing electric power has both advantages and disadvantages for landfill operators. Noise from IC engines had resulted in complaints from citizens that have caused IC engines to be shut down and the LFG to be flared again. In the 1980’s landfills were able to secure contracts to sell electric power for