(374a) Life-Cycle Analysis of Low-Carbon Hydrogen Supply Pathways for the Provision of Heat in Buildings

Decarbonization of the buildings sector in the global economy presents an inherent challenge due to the efforts required to shift from existing fuels and infrastructure to lower-carbon alternatives at both the consumer and system-levels. In this context, recent evidence from the United Kingdom indicates that hydrogen may have a complementary role to electricity in a cost-effective hybrid-heating system [1]. Studies have shown that a significant portion of this hydrogen is likely to be sourced from natural gas reforming with carbon capture and storage (CCS) in the near-term to reduce fuel costs [2][3]. More recently, advanced natural gas reforming processes with higher CO₂ capture rates have been proposed as an economical interim solution to scale-up the use of hydrogen before alternative technologies such as renewable-based water electrolysis are matured over time. However, the overall environmental implications of these processes are poorly understood as previous studies have not accounted for the associated infrastructure requirements. In general, further analysis is required to understand the lifecycle impacts of the fuel supply, H₂ and CO₂ storage infrastructure, and operating practices across different regions for informed decision-making. To this end, this paper presents a comparative lifecycle assessment (LCA) of five different hydrogen supply pathways for meeting the heating demands in the North of England.

The LCA is based on attributional modelling and focuses on cradle-to-gate analysis for the following pathways: a) steam methane reforming (SMR) with CCS, b) autothermal reforming (ATR) with CCS, c) water electrolysis using offshore wind power, d) water electrolysis using grid power, and e) water electrolysis using offshore wind and grid power in a hybrid system. The scope of the H21 North of England project, which is an industry feasibility study, informs the modelling of technical parameters for the supply infrastructure in the inventory dataset. We combine published literature with process inventory modelling to represent various lifecycle stages in the LCA software, SimaPro. Version 3 of the ecoinvent database was used to model the inventory data for background processes and ReCiPe 2016 was used to characterize the impacts using midpoint indicators. The supply pathways were compared on key performance metrics such as global warming potential, fine particulate matter formation, freshwater ecotoxicity, mineral resource scarcity, etc., to estimate and benchmark their overall performance. Preliminary findings suggest that water electrolysis using offshore wind power has the lowest global warming potential as reported in previous literature [4]. However, both SMR and ATR with CCS may result in a CO₂ footprint, which is 2 – 3 times that of water electrolysis using offshore wind. Water electrolysis with grid power has the potential to be low-carbon only when the electricity grid is near zero-carbon. Furthermore, the results stress the need to lower other environmental impacts linked to the offshore wind supply to minimize its impact on freshwater ecosystems and mineral resources. More generally, greenhouse gas emissions associated with the natural gas supply chain and the electricity grid have the potential to increase the global warming potential of both SMR and ATR processes by up to a factor of five depending on the country of operation. Therefore, efficient management of the fuel supply chains and accelerated progress in their decarbonization contributes to the gradual transition of the buildings sector towards net-zero emissions.

[1] Climate Change Committee, “The Sixth Carbon Budget - The UK’s path to Net Zero,” 2020.

[2] N. Sunny, N. Mac Dowell, and N. Shah, “What is needed to deliver carbon-neutral heat using hydrogen and CCS?,” Energy Environ. Sci., vol. 13, no. 11, p. 4204, Nov. 2020, doi: 10.1039/d0ee02016h.

[3] M. Thompson et al., “Hydrogen in a low-carbon economy,” 2018.

[4] E. Cetinkaya, I. Dincer, and G. F. Naterer, “Life cycle assessment of various hydrogen production methods,” Int. J. Hydrogen Energy, vol. 37, no. 3, pp. 2071–2080, Feb. 2012, doi: 10.1016/j.ijhydene.2011.10.064.