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Life Cycle Assessment and Cost Analysis of Anaerobic Co-Digestion of Food Waste at a Medium-Scale Water Resource Recovery Facility
Citation:
Morellis, B., S. Cashman, Cissy Ma, J. Garland, AND J. Turgeon. Life Cycle Assessment and Cost Analysis of Anaerobic Co-Digestion of Food Waste at a Medium-Scale Water Resource Recovery Facility. ACLCA conference XVIII, Fort Collins, Colorado, September 25 - 28, 2018.
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. Communities and states throughout the United States are leveraging diverse strategies to manage and transform waste streams to avoid landfilling and incineration. Several states, including Massachusetts, have instituted landfill waste bans forcing large commercial waste generators to find alternative reuse and recovery options for their organic waste. Given this directive, it is essential that we understand the net impact of the alternative treatment options. This study assesses the life cycle environmental and cost benefits and burdens of expanding anaerobic digestion capacity at a medium-scale water resource recovery facility (WRRF) for co-digestion of source separated organic (SSO) waste. The SSO waste is fed directly into an anaerobic digester where it generates biogas and additional solids. A combined heat and power (CHP) system is utilized to provide facility heat and net-metered electricity. Biosolids are processed in a thermal drying facility, producing pelletized fertilizer for easy transport and field application. The analysis calculates the avoided disposal burdens for organic waste landfill and waste-to-energy disposal. Life cycle cost analysis (LCCA) results demonstrate the economic effectiveness of investing in additional digester capacity and CHP systems to produce biogas and leverage Massachusetts State programs for net metering and renewable and alternative energy credits, yielding a payback period of less than 5 years in the baseline scenario. The WRRF realizes potential environmental benefits (negative impact results) for three of eight impact categories including cumulative energy demand and climate change potential when the full capacity of digesters is utilized. Other impact categories demonstrate reductions in environmental impact potential, except for eutrophication potential where nutrient removal would be required to mitigate increased nitrogen and phosphorus emissions associated with increased waste acceptance. Study results support the use of anaerobic digestion as an environmentally preferable alternative to landfill and WTE disposal for most impact categories within the context of a waste ban.
Description:
Communities and states throughout the United States are leveraging diverse strategies to manage and transform waste streams to avoid landfilling and incineration. Several states, including Massachusetts, have instituted landfill waste bans forcing large commercial waste generators to find alternative reuse and recovery options for their organic waste. Given this directive, it is essential that we understand the net impact of the alternative treatment options. This study assesses the life cycle environmental and cost benefits and burdens of expanding anaerobic digestion capacity at a medium-scale water resource recovery facility (WRRF) for co-digestion of source separated organic (SSO) waste. The SSO waste is fed directly into an anaerobic digester where it generates biogas and additional solids. A combined heat and power (CHP) system is utilized to provide facility heat and net-metered electricity. Biosolids are processed in a thermal drying facility, producing pelletized fertilizer for easy transport and field application. The analysis calculates the avoided disposal burdens for organic waste landfill and waste-to-energy disposal. Life cycle cost analysis (LCCA) results demonstrate the economic effectiveness of investing in additional digester capacity and CHP systems to produce biogas and leverage Massachusetts State programs for net metering and renewable and alternative energy credits, yielding a payback period of less than 5 years in the baseline scenario. The WRRF realizes potential environmental benefits (negative impact results) for three of eight impact categories including cumulative energy demand and climate change potential when the full capacity of digesters is utilized. Other impact categories demonstrate reductions in environmental impact potential, except for eutrophication potential where nutrient removal would be required to mitigate increased nitrogen and phosphorus emissions associated with increased waste acceptance. Study results support the use of anaerobic digestion as an environmentally preferable alternative to landfill and WTE disposal for most impact categories within the context of a waste ban.