Potential for mitigating GHG emissions at a Swedish wastewater treatment plant – a life cycle approach

To meet the national and international climate goals every potential GHG mitigating effort needs to be addressed. The aim of this thesis is to investigate if the wastewater treatment plant (WWTP), Ekebyhov, can reduce its GHG emissions by making changes inthe treatmentprocess. The main GHGs emitted from WWT areN2O, CH4and CO2. To begin with, Ekebyhov’scurrent carbon footprintwas calculated in a base line scenario, using a calculation tool (ECT). The results showed that the total footprintamounted to 522 tons CO2eqper year, with the majority of the emissions (83 %) from the activated sludge process. Five GHG-mitigating measures were identified and potential GHG emission reduction (PGER) was calculated from 1) optimized WWT, 2) urea treated sludge, 3) change of chemicals, 4) green transports and 5) added anaerobic digestion (AD) process. The largest PGER came from added AD, followed by optimized WWT. Finally, the PGER for all measures was calculated and resulted in net negative emissions of -95 tons CO2eq per year. The thesis shows that it is possible to reduce the carbon footprint of Ekebyhov WWTP, even to a net negative result. It is, however important to address other impact categories in a full LCA to be able to make fully informed decisions