Comparative environmental and economic life cycle assessment of high solids anaerobic co-digestion for biosolids and organic waste management

Abstract

High-Solids Anaerobic co-Digestion (HS-AcD) of sewage sludge (biosolids) with the organic fraction of municipal solid waste is a promising waste management alternative due to high methane yields, lower reactor volume requirements, lower energy inputs, and less leachate production than liquid anaerobic digestion. This study evaluated the environmental and economic burdens and benefits of HS-AcD of biosolids, Food Waste (FW), and Yard Waste (YW) using Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) methods using Hillsborough County, Florida in the U.S. as a case study. Results for HS-AcD were compared with incineration, composting, and landfilling, with and without landfill gas use. The results showed that HS-AcD of a mixture of biosolids, FW, and YW had the lowest environmental impacts in all categories analyzed (global warming potential, acidification, eutrophication, and ecotoxicity). In terms of economics, HS-AcD had the lowest life cycle cost, with or without considering land acquisition. The results show that HS-AcD is the best choice to manage biosolids and the organic waste in Hillsborough County in terms of both environmental and economic sustainability.

Keywords: Biosolids; High solids anaerobic co-digestion; Life cycle assessment; Life cycle cost analysis; Organic fraction of municipal solid waste.