Environmental and community impact assessment of operations at an organic waste-to-energy facility

State and local governments have set ambitious waste diversion goals to mitigate landfill methane emissions. In California, Senate Bill 1383 requires a 75% reduction in organic waste landfilling by 2025. This goal requires significant growth in organic waste recycling facilities throughout the state. Anaerobic digestion (AD) of organic municipal solid waste is an important waste diversion strategy. However, the operation of AD facilities and subsequent treatment of solid digestate are associated with emissions of malodorous compounds and air toxics. Because municipal organic waste is primarily generated in densely-populated areas, these facilities are often sited near cities to reduce hauling distances. To minimize the environmental and community impacts of expansion and new construction of organic waste processing facilities, it is critical to characterize emission sources at various waste processing stages, identify influential sources that limit facility scale-up, and develop mitigation priorities and siting strategies.

This study combines source monitoring and dispersion modeling to understand the offsite odor and air toxics impacts associated with emissions from different waste processing stages at an enclosed dry (high-solids) AD facility, including trucking, waste sorting, digestion, and composting. We develop a framework using the EPA's AERMOD plume model to link source emissions to their offsite impacts on surrounding communities. We develop an empirical relationship between the emission levels and the separation distances required to protect communities from odor annoyances. The resulting framework is then extrapolated to 25 prototypical sites throughout California to account for diverse weather and terrain conditions to support AD siting decisions. The modeled ground level H2S concentrations do not pose a health concern. However, outdoor composting can have significant odor impacts and may be a limiting factor in the facility scale-up. Our study provides unique data and analysis framework to guide best practices and mitigation priorities in organic recycling industries.