F. Naaz, J. Zhang, U. Singh, T.R. Hawkins
Argonne National Laboratory,
United States
Keywords: biomass waste resource, anaerobic digestion, renewable natural gas, GHG emission mitigation
Summary:
The biomass waste availability, waste management practices, and energy needs vary significantly by states, depending on urbanization, industrialization, and agricultural activities. As a result, this study explores state-level biomass waste resources and strategies to mitigate greenhouse gas (GHG) emissions through the production of renewable natural gas (RNG) via anaerobic digestion (AD) and biogas upgrading. Key waste categories analyzed include municipal food waste (MFW) dumped in landfills, livestock waste (LSW), and wastewater resource facilities sludge (WRRF-S). From this study, it has been found that the U.S. generates 2.07 × 10^9 MT biomass waste (wet basis) annually, comprising 1.13 × 10^8 of MT MFW, 1.71 × 10^9 MT of LSW, and 2.49 × 10^8 MT of WRRF-S (wet basis). In addition, to evaluate the GHG emission potential, wet wastes were categorized into two categories: waste managed under current business-as-usual practices (excluding AD) and waste managed in existing AD facilities but not yet converted to RNG. This classification provides insights into the additional potential for utilizing wet waste in AD systems, as well as the amount already processed for biogas production via AD that can be upgraded to RNG. It indicates that 2.0 × 10^9 MT (wet basis) of biomass waste is available for RNG production via AD, as it is not currently treated in AD systems to produce biogas. Additionally, 8.16 × 10^7 MT (wet basis) of biomass waste has already been processed in existing AD systems and holds the potential to be upgraded to RNG. The findings highlight a significant potential to reduce the overall GHG emissions by 5.03 × 10^2 MMT of CO2 equivalent annually by converting the wet biomass waste to RNG, including the biogas upgrading of waste that is already treated at current AD plants. However, the study identifies challenges in improving the sludge-to-RNG production system and the need for better infrastructure integration. It also notes that upgrading biogas from existing AD facilities to RNG also requires the control on methane leakage. The research provides insights that can guide local and national climate policies, emphasizing the role of waste resource management in reducing GHG emissions.