| A life-cycle inventory methodology was developed and used to quantify total system materials, energy, costs and flows to the environment from acquiring, using and decommissioning five systems currently used for managing food waste. The default position for food waste management is the municipal solid waste (MSW) system; the food waste disposer (FWD), an appliance installed in kitchen sinks, diverts food waste from MSW to wastewater systems. Because a FWD is part of wastewater collection, total impacts include impacts from both collection and treatment/disposal. The five systems inventoried are a rural wastewater on-site system (FWD/OSS); a municipal wastewater system (FWD/POTW); and three MSW systems--MSW Collection/Compost; MSW Collection/Waste-to-Energy (WTE); and MSW Collection/Landfill. The five systems were ranked from low (#1) to high (#5) for twelve parameters per 100 kg of food waste-land, total system materials, water, total system energy, total system cost, air emissions, acid gases, greenhouse gases, wastewater, waterborne wastes, solid wastes and food waste byproducts (sludge, septage, compost, ash, landfill residues). The overall ranking (MSW Collection/Compost, MSW Collection/Landfill, FWD/POTW, MSW Collection/WTE, and FWD/OSS) agreed reasonable well with the ranking by cost, The rural FWD/OSS ranked highest, because 100 kg of food waste and associated carrier water represent a larger fraction of total solids and wastewater passing through this system over its design life. The MSW Collection/WTE system ranked second; burning food waste yields little exportable energy if system energy losses are included. The FWD/POTW system ranked third; first for byproducts (sludge) requiring managing, but low for land, materials, energy, and air emissions, and solid waste. The MSW Collection/Landfill system ranked second lowest for cost, but low also for water, wastewater, waterborne wastes, total air emissions, and food waste byproducts (landfill residues). The MSW Collection/Compost system ranked lowest, but is a non-essential system. For all systems but the FWD/OSS, over 85% of the total flows to the environment are attributable to food waste and system use, less than 10% to energy sources and 5% to materials. Materials contribute almost half the FWD/OSS flows. |
