An LCA of alternative wastewater sludge treatment scenarios

Life Cycle Assessment (LCA) was carried out in order to compare the environmental impacts of five alternative treatment scenarios of sewage sludge in the French context. The scenarios were composed of one main process (incineration, agricultural land application, or landfill), one stabilization process (lime stabilization, composting, or anaerobic digestion) and transports of sludge. Average data on literature, real site data and simulation result were used for accomplishing the assessment. The indicator results of environmental impact were normalized by reference contributions of one person in the West-Europe over I year in order to better understand their relative magnitude. The normalization results were finally weighted to give one aggregated result of the comparative LCA with sensitivity analysis on the weighing factors. The study result showed: the combination of anaerobic digestion and agricultural land application was most environmentally friendly tanks to less emissions and less consumption of energy; the most important substances contributing to human toxicity and ecotoxicity were heavy metals released from the atmospheric effluent of incineration and from the sludge applied to agricultural fields; finally appropriate tools were required to control the non-point-source pollutants like the methane of the dispersed landfill gas and the effluent gases of transport vehicles. (C) 2002 Elsevier Science B.V. All rights reserved.