Decarbonizing Heating at Municipal Wastewater Treatment Plants with Power-to-Heat : Techno-Economic and Environmental Evaluation of Heat Pumps and Electric Boilers

Sammanfattning

Municipal wastewater treatment plants (WWTPs) in cold climates often rely on fossil fuels to meet seasonal heating demands, especially during winter months when biogas production is insufficient. The Ernemar WWTP in Oskarshamn, Sweden, exemplifies this challenge—burning heating oil in winter while flaring surplus biogas during summer. This seasonal mismatch leads to avoidable greenhouse gas emissions and increased operational costs. This thesis presents a techno-economic case study evaluating Power-to-Heat (P2H) technologies—specifically heat pumps and electric boilers—as low-carbon alternatives for decarbonizing heating at the Ernemar WWTP. Using real plant data, local climate conditions, and technology performance parameters, the study models different design configurations to simulate load sharing, investment needs, energy costs, and emission reductions. The analysis identifies a hybrid solution—combining a 100kW heat pump for base and intermediate loads with a 150kW electric boiler for peak demands—as the most effective setup. This system can fully replace oil-based heating during winter, reducing CO2 emissions by 98.1% and cutting operational costs by 74%, with a payback period of 6.55 years and a net present value of 319,464 SEK over ten years. Sensitivity analyses confirm the robustness of the solution under varying economic and technical assumptions. The findings demonstrate that Power-to-Heat integration is both technically feasible and financially justifiable for small to mid-scale WWTPs, offering a practical pathway to support municipal decarbonization goals using commercially available technologies.