Feasibility of alternative sewage sludge treatment methods from a lifecycle assessment (LCA) perspective

Abstract

Abstract Sewage sludge treatment and disposal are critical global issues, with concerns including sludge volume/weight, release of pollutants, and other environmental impacts. This study develops a semi-quantitative assessment methodology for selecting appropriate sludge treatment options on the basis of a lifecycle assessment approach. Various biological, chemical, thermal, and thermo-chemical sludge treatment methods described in the literature are reviewed and evaluated holistically by adopting the developed methodology to determine their comparative effectiveness in reducing sludge volume/weight and environmental impacts. Anaerobic digestion, pyrolysis, and supercritical water oxidation are found to be the best-performing treatment methods. They are not only more effective in reducing sludge volume/weight and pollutants but also have lower global warming and toxicity potential compared to most of the other methods reviewed. The potential for adverse environmental effects remains owing to the release of pollutants when the products of sludge treatment are utilised, e.g. as soil amendments or fuel. This necessitates further investigation to explore the toxicity impacts of a wider array of emerging pollutants from a lifecycle perspective as well as further development of sludge treatment methods to overcome the drawbacks of existing methods.