Food Waste End-of-Life Management: Comparing Co-Digestion at a Wastewater Treatment Facility with Composting, Landfilling, and Waste-to-Energy Combustion - Cambridge, MA
Citation:
Cashman, S., B. Morelli, Cissy Ma, J. Garland, AND J. Turgeon. Food Waste End-of-Life Management: Comparing Co-Digestion at a Wastewater Treatment Facility with Composting, Landfilling, and Waste-to-Energy Combustion - Cambridge, MA. Presented at City of Cambridge Science in the City meeting, Cambridge, MA, April 23, 2021.
Impact/Purpose:
To explore the environmental impacts and life cycle cost of co-digestion energy recovery from food waste in medium scale wastewater treatment facility. The stakeholders that would be interested in this study and apply the results including local communities; utilities, OW; OWM; Regions; LCA practitioners, decision makers, academia; experts.
Description:
The presented research uses life cycle assessment and life cycle cost (LCC) analysis to evaluate a Massachusetts wastewater treatment facility, treating 23.5 million gallons per day, upgrading to a water resource recovery facility (WRRF). The facility recently installed additional anaerobic digestion (AD) and co-generation capacity, allowing acceptance of source separated organics (SSO), boosting biogas production, and avoiding traditional food waste disposal. Inventory data were developed using plant records and GPS-X™ modeling software. Results are presented for eight environmental impacts and LCC, focusing on cumulative energy demand and global warming potential, and comparing two co-digestion feedstock scenarios against WRRF operation before plant upgrades. Scenario and sensitivity assess the effect of SSO acceptance rate, AD performance, avoided disposal, and cost parameters on results. Upgrades for SSO co-digestion reduce environmental impacts and system operating cost in six of eight environmental impact categories under baseline AD performance. Eutrophication potential impact results increase (by 10-24 percent) due to co-digestion. Results in all other impact categories yield net environmental impact reductions. System net present value decreases moderately, by 6 to 12 percent, corresponding to payback periods of between nine and 18 years for equipment upgrades. Feedstock acceptance rate and digester performance affect the magnitude of impacts, but scenario results indicate a consistent downward trend in impacts with only a few exceptions, which occur under low AD performance. Sensitivity results demonstrate the benefit of food waste digestion as compared to alternative disposal options, reinforcing the concept of resource recovery hubs to increase sustainability and resiliency.