Using the Life Cycle Assessment Methodology for a Comprehensive Evaluation of Energy Demand in Wastewater Treatment

Previously, the analysis of energy demand for wastewater treatment was often limited to onedimensional analyses of electricity demand. However, a comprehensive analysis requires the inclusion of all different contributions to energy demand, such as the energy required to produce chemicals (e.g. coagulants and flocculants) and transport sludge, and the additional fuels needed to dry sewage sludge. System boundaries must be expanded to include upstream and downstream processes in order to capture all relevant contributions to energy demand. Additionally, a comprehensive analysis accounts for secondary products of wastewater treatment: the production of electricity from digester gas, the recycling of nutrients and water to agriculture, and the substitution of fossil fuels in sludge co-incineration. The Life Cycle Assessment (LCA) methodology defined in ISO 14040/44 is a suitable tool for this task. With it, all different primary and secondary energy demands can be quantified and assessed using consistent indicators, complemented by an assessment of other environmental impacts such as the greenhouse effect.