Life cycle assessment of traditional and innovative sludge management scenarios in Australia: Focusing on environmental impacts, energy balance, and economic benefits

Abstract

Sludge, as a sustainable energy source and pollutant matrix, necessitates effective management. The environmental, energy and economic impacts of sludge management practices in Australia remained unknown. Furthermore, lignosulfonate addition was recently reported as a promising approach to enhance the energy production from sludge, the environmental, energy and economic benefits of which on sludge management have not been explored. Life cycle assessment of four scenarios: two traditional (A: land application of digested sludge, B: composting of digested sludge before land application) and two innovative (A and B with lignosulfonate addition during the digestion process - C and D) was conducted. Traditional scenario A outperformed scenario B, with a 2.24-fold reduction in environmental footprints, 16.28-fold higher energy recovery, and reduced expenditure reaching $78.23/t dry sludge (DS). Scenario C demonstrated superior results with a 1.26-fold decrease in environmental footprints, 1.51-fold more energy recovery than A, and a shift to economic benefits of$5.36/t DS. Sensitivity analysis revealed scenario C was sensitive to sludge's total and volatile solids content, highlighting the importance of optimization for best performance. These findings guide environmentally and economically viable sludge management, emphasizing efficient energy recovery