Impact of methane leakage rate and carbon capture rate on blue hydrogen sustainability using combined warming index

Blue hydrogen may become important to achieve decarbonisation targets. Yet, the uncertainty and aggregated impact of methane leakage rate and carbon dioxide capture rate on the value of blue hydrogen from a whole systems perspective has not been investigated. Our study focuses on the impact of the dual influence of these variables in an energy system model of the United Kingdom (UK). We incorporate practical ranges for methane leakage rate and carbon capture rate and analyse their impact by formulating a novel parameter, termed the Combined Warming Index (CWI). The CWI can be used to assess decarbonisation scenario outputs from energy system models giving insights into their effects on the dynamics of energy system and decarbonisation parameters. Our results suggest that sustainable deployment of blue hydrogen becomes threatened at a carbon capture rate of 85 % and across the range of methane leakage rates of 0.125 %, 0.5 %, 1 %, 1.5 % and 2.5 %. At a carbon capture rate of 90 %, and methane leakage rates at 1 %, 1.5 % and 2.5 %, blue hydrogen is not significantly deployed to 2050. Methane leakage rate and carbon capture rate are key parameters for the success of blue hydrogen as a low-carbon hydrogen option, and although carbon capture rate is the more critical parameter, methane leakage rate is also important but becomes a secondary concern in natural gas supply chains with low fugitive emissions. The outcome of our research can contribute to framing relevant policy for the application of CCS technology as society seeks to attain low-carbon economy aims.