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Food Waste End-of-Life Management: Comparing Co-Digestion at a Wastewater Treatment Facility with Composting, Landfilling, and Waste-to-Energy Combustion
Citation:
Cashman, S., B. Morelli, Xin 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. ACLCA conference XIX, Tucson, AZ, September 24 - 26, 2019.
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:
Communities throughout the U.S. are shifting from the paradigm of waste disposal to viewing “waste” as a resource. Massachusetts has recently banned the disposal of organic materials from large commercial and industrial waste generators in a landfill or incinerator. In light of this ban, several industries are vying for the opportunity to utilize abundant organic waste streams. The presented research uses life cycle assessment and life cycle cost analysis to evaluate a Massachusetts wastewater treatment facility (WWTF), treating 23.5 million gallons per day, as it upgrades for resource recovery. The facility recently installed additional anaerobic digestion (AD) and combined heat and power (CHP) capacity, allowing acceptance of source separated organic (SSO) waste, boosting biogas production, and avoiding traditional food waste disposal. The planned capacity of the AD project will allow the facility to accept 40% of the current organic material available in the greater Boston region. We also analyze composting through windrow and aerated static pile (ASP) systems as an alternative disposal pathway for food waste. Co-digestion and composting are then compared to legacy food waste treatment options such as landfill and waste-to-energy combustion. The WWTF inventory data were developed using plant records and GPS-X™ modeling software. For the WWTF, results are presented for eight environmental impacts and life cycle cost, focusing on cumulative energy demand, global warming potential, eutrophication potential, and comparing two co-digestion feedstock scenarios against WWTF operation prior to plant upgrades. Scenario and sensitivity analyses assess the effect of SSO acceptance rate, AD performance, avoided disposal processes, and cost parameters on results. Upgrades for SSO co-digestion reduce plant-wide environmental impacts and system operating cost in six of eight environmental impact categories considering baseline AD performance. Eutrophication potential impact results increase (by between 10 and 24 percent) due to co-digestion. Results in all other impact categories yield net environmental impact reductions. System net present value decreases moderately compared to historical operational costs corresponding to payback periods of between 14 and 27 years for equipment upgrades. Sensitivity results demonstrate the benefit of food waste co-digestion as compared to disposal via landfilling or waste-to-energy combustion. Food waste composting requires much lower capital costs compared to co-digestion, but is not able to capture the energy potential and associated environmental benefit of food waste energy recovery through co-digestion.