Life-Cycle Assessment of a biogas power plant with application of different climate metrics and inclusion of near-term climate forcers

Abstract

In this project we investigate the environmental sustainability associated with the production of electricity through anaerobic co-digestion of sewage sludge and other organic wastes under Norwegian conditions. We provide a state-of-the-art life-cycle assessment based on primary data received from a biogas plant located in Drammen, Norway supplemented with data from literature. The functional unit was 1MJ of electricity and within the system boundaries we included the feedstock transportation, the production of biogas and digestate as well as the management and end-use for both by-products. Since heat is used only internally and the digestate doesn t have at the moment a sale value in Norway, we did not used allocations. For the estimation of the emissions occurring during the storage and spreading of the digestate we used the approach from The Intergovernmental Panel on Climate Change together with data from literature. We investigate the sensitivity of the system to the critical parameters and provide five different scenarios. Our results indicate as hotspots the management of the digestate, mainly the open storage together with the methane losses during the anaerobic co-digestion. We explore the robustness of the assessment s results to both global warming potential and global temperature change potential for a short-term and a long-term time horizon. As a novelty, in this study we also quantify beside the impact from well-mixed greenhouse gases, which are usually taken into account in life-cycle assessment studies, the impact from near-term climate forces.