Measuring landfill gas collection efficiency is important for gauging emission control effectiveness and energy recovery opportunities. Though researched for years, practical measures of collection efficiency are lacking. Instead, a default efficiency of 75% based on surveys of industry estimates is commonly used, for example, by the United States Environmental Protection Agency (US EPA). Though few, actual emission measurements indicate substantially higher efficiencies ranging from 85 to 98%.The scarcity of collection efficiency measurements is due to their difficulty and cost. The Los Angeles County Sanitation Districts (Districts) developed a measure of collection efficiency using readily acquired surface methane concentrations and the US EPA's Industrial Source Complex (ISC) model. This methodology was recently applied to estimate landfill gas collection efficiency at a Districts landfill and indicates an efficiency approaching 95% or greater.ISC model setup and application are described as well as model assumptions and their validity. Uncertainties in the model parameters and their effect on the collection efficiency calculation are presented. The significance and implications of this study are discussed.
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