Life cycle assessment of Irish district heating systems: a comparison of waste heat pump, biomass-based and conventional gas boiler

• DOI: 10.1007/s10098-021-02257-y
• Publication Date: 2022-01-17T00:03:47Z
• Authors: Conall Mahon; Maneesh Kumar Med...; Donna Gartland; Fionnuala Murphy
• Keywords: Heating system; Biogas

Abstract This paper presents a life cycle assessment (LCA) of heat supply scenarios for the replacement of fossil-based energy systems through a case study focusing on an existing gas-fired boiler supplying heat for buildings located in Tallaght, Ireland. The three replacement systems considered are a waste heat fed heat pump district heating system (WHP-DH), a biomass CHP plant district heating system (BCHP-DH), and an individual gas boiler system (GB). The study found that both DH systems have lower environmental impact than the GB, with the BCHP-DH being superior to WHP-DH. However, using 2030 electricity data showed almost similar overall impacts for both the DH systems. Human toxicity potential (HTP) was highest among all impact categories studied and was due to the large additional infrastructure requirement for all three systems. Whereas the other impacts; Global warming (GWP), Fossil fuel depletion (FFD) and Eutrophication (EP), were due to involving usage of natural gas and electricity in use phase. The BCHP-DH showed reduced greenhouse gas (GHG) emissions by 45% and FFD by 73% compared to the GB system. Using 2030 electricity data, the WHP-DH decreased GHG emissions by 42% and FFD by 47%. Further, replacing biomethane with the natural gas in the DH systems decreased GWP by at least 11.4%. The present study concludes that the environmental benefit of a DH system is largely dependent on the carbon intensity of the electricity it uses, thus recommending the DH systems for large scale retrofitting schemes in Ireland to reach Europe’s 2030 GHG reduction targets.