Selecting the best technology for a landfill gas (LFG) project involves consideration of several key design factors, beginning with estimating the LFG gas recovery potential for the landfill. In general, the volume of waste controls the potential amount of landfill methane that can be extracted from the landfill. Local conditions, LFG gas collection efficiency and the flow rate for the extracted landfill biomethane also significantly influence the types of technologies and end use options that are most feasible for a project. Landfill Gas Collection is described in detail in a separate tab.
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Before LFG can be used in an energy conversion process, it must be treated to remove condensate, particulates and other impurities. Treatment requirements depend on the end use. Landfills that are selling gas for beneficial use and are subject to gas collection and control requirements under federal MSW landfill rules (40 CFR part 60, federal or state plan implementing 40 CFR part 60, or 40 CFR part 63 ) are required to develop a site-specific treatment monitoring plan and keep records of the parameters noted in the plan.
• Gas treatment for LFG gas electricity projects typically include a series of filters to remove contaminants that can damage the engine or turbine and reduce efficiency.
• Minimal treatment is required for direct use of landfill biogas in boilers, furnaces or kilns (direct use).
• Advanced treatment is needed to produce renewable natural gas (RNG)
for injection into natural gas pipelines or production of alternative fuels. The most growth is currently occurring in RNG applications.
Treatment systems can be divided into primary and secondary treatment processing. Most primary processing systems include de-watering and filtration (required for electricity generation). Gas cooling and compression have been used for many years and are standard elements of active landfill gas collection systems. Secondary treatment systems are designed to provide greater landfill methane cleaning than is possible using primary systems alone. Secondary landfill gas treatment systems may employ both physical and chemical treatments. The type of secondary treatment depends on the constituents that need to be removed for the end use. Two of the trace contaminants that may have to be removed from LFG gas are siloxanes and sulfur compounds, which can significantly increase the cost of landfill gas to energy project.