Citation:

Birney, C., J. Vendries, B. Young, A. Beck, AND W. Ingwersen. Fusing USEPA Waste Models: Hybrid Waste Life Cycle Assessment Models. Presented at International Symposium on Sustainable Systems and Technology (ISSST) 2023, Fort Collins, CO, June 12 - 15, 2023.

Impact/Purpose:

To present research on evaluating how to improve WARM and REI-WIO by fusing parent models with USEEIO at ISSST 2023.

Description:

The generation of municipal solid waste (MSW) in the US is increasing, putting pressure on environmental and human health. Reducing waste generation and prioritizing waste management pathways alternative to landfilling could ease the environmental burden of MSW. USEPA has developed multiple waste life cycle (LCA) models to estimate the direct and indirect environmental and economic effects of waste management pathways. These models include Waste Reduction Model (WARM), the waste input-output model underlying the Recycling Economic Information Report (REI-WIO), and US Environmentally-Extended Input-Output Model (USEEIO). USEPA also maintains the quantitative model behind the Facts and Figures (FF) report, which estimates annual MSW generation and treatment. These models use unique data and assumptions to represent US solid waste generation and management, each with their limitations. We evaluate how to improve the parent WARM and REI-WIO models by integrating the parent models with USEEIO, a family of life cycle models of US goods and services. We create multiple prototype hybrid input-output (HIO) models, including an integrated hybrid, a disaggregated mixed-unit hybrid, and a supply-use framework waste input-output hybrid, built to evaluate food and concrete waste management. HIO models generally refer to life cycle models incorporating economic input-output data and physical data. These new HIO models evaluate the direct and indirect impacts of waste management pathways by material on greenhouse gas emissions, employment, wages, and taxes. The hybrid models are developed in Python and publicly available in a GitHub repository (https://github.com/USEPA/HIO). We first harmonize WARM, REI-WIO, USEEIO, and FF by defining concordances between each model’s waste-generating sectors, waste management pathways, and waste materials in the open-source Flow Sector Attribution (FLOWSA) Python package (https://github.com/USEPA/flowsa). Waste-generating sectors and waste management pathways are generally assigned to North American Industrial Classification (NAICS) codes, while materials are assigned to a standardized nomenclature. We generate new Flow-By-Sector models in FLOWSA using the concordances to fuse, or combine ,the USEPA waste models to calculate waste flows between waste-generating sectors and waste management pathways. The Flow-By-Sector models provide insight into each pathway’s direct environmental and economic impacts. The Flow-By-Sector model results are used as inputs into the new HIO models to evaluate the direct and embedded environmental and economic impacts of food and concrete waste for landfilling, concrete recycling, food waste combustion, food waste composting, and food waste anaerobic digestion. The results and capabilities of the HIO models are compared with the parent WARM and REI-WIO modes. The integrated hybrid environmental assessment results are comparable to WARM while differing greatly from the other hybrid models. The hybrid models provide additional functionality beyond what the parent models provide, and the hybrid models allow for sharing common background components. However, the methods behind the hybrid models create varying model results for assessing the environmental and economic impacts of managing waste. The USEPA is continuing to evaluate the methods and results of the prototype HIO models to assess the best hybrid model to use to calculate the impacts of MSW. Future work could expand the materials and waste management pathways in the analysis.

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