A Life Cycle Analysis of District Heating Options for Western Washington University

Abstract

This study examined two replacement options for the district heating system at Western Washington University based on CO2e emissions savings and system feasibility. Life cycle assessment was used to compare a nodal air source heat pump system with supplemental geo-exchange and a nodal air source heat pump system with water preheated from waste heat sources. The systems were also compared at their designed water temperature of 120, and at a temperature of 180, with natural gas used to boost the water temperature. This work adds to the body of knowledge for universities seeking to replace aging steam-based heating system. It provides results about the feasibility of incrementally upgrading heating systems and using geothermal and waste heat sources at a university scale. The EcoInvent 3.11 systems library, the Recipe Endpoint (H/A), and IPCC 2021 GTP 100 V1.03 methods were used for the LCA. I found that in both the geothermal and waste heat cases, the high temperature scenarios resulted in high emissions of 554kton CO2e and 377kton CO2e, respectively, over the 50-year project lifetime. The Business-As-Usual case, which assumes WWU continues to use the natural-gas-powered steam plant, produced 468kton CO2e over 50 years. For low-temperature scenarios, the geothermal system produced 240kton CO2e over the project lifetime, and the waste heat system produced 120kton CO2e. The emissions for the construction of all scenarios were under 14kton CO2e. These results show that the high-temperature scenarios are not appropriate options due to their high emissions of 118% of the BAU emissions for the geothermal scenario, and 82% of the BAU emissions for the Port scenario. The results also show the Port low-temperature scenario has the lowest emissions of all use scenarios, 120kton CO2e, and is therefore the recommended option for WWU