Comparative modeling of greenhouse gas emissions from source-separated organics: A case study in New York City

Many urban areas are interested in quantifying the greenhouse gas (GHG) footprint of their organic waste management systems. The biosolids emissions assessment model (BEAM) offers a means to model emissions associated with organic waste management systems and compare the GHG footprints of different management options. In this paper we present a case study detailing a GHG assessment we conducted for the New York City Department of Environmental Protection (NYC DEP) to compare GHG emissions associated with options for managing source-separated organic (SSO) wastes generated by New York City (NYC). We modeled five options in BEAM using real-world data provided by NYC: (1) landfilling raw SSO, (2) composting then land-applying SSO (3) digesting then landfilling SSO, (4) digesting then land-applying the digested SSO or (5) digesting then composting and land-applying the composted SSO. Model inputs include the characteristics of the biomass that NYC DEP is handling, local factors including the carbon intensity of electricity and the climate in which landfills are located, and published data on GHG emissions associated with the modeled management options. Results show a range of GHG footprints, from -0.59 to 2.16 Mg carbon dioxide equivalents (CO₂eq) per dry Mg of SSO demonstrating the high impact that management decisions can have on the GHG footprint of organic waste management. The options in which biomass was land-applied instead of landfilled (Options 2, 4, and 5) offered the most favorable GHG footprints. This study also illustrates how BEAM can serve as a decision-support tool to guide waste management decisions.