Environmental Research Letters (Jan 2022)
Is hydrogen production through natural gas pyrolysis compatible with ambitious climate targets in the United States? A location-specific, time-resolved analysis
Abstract
Pyrolysis of natural gas to produce H _2 and solid carbon through methane cracking can be characterized as a high-CH _4 , low-CO _2 process. It results in low CO _2 emissions because no direct CO _2 is generated at the point of H _2 generation if solid carbon is not combusted further. However, it results in high CH _4 emissions because of its higher natural gas consumption compared to the direct use of natural gas and, thus, higher CH _4 losses along the natural gas supply chain. Here, I analyzed whether this process can provide climate benefit in comparison to the direct, unabated utilization of natural gas and also in comparison with H _2 produced from water electrolysis with grid electricity. To this end, Monte Carlo simulations of time-resolved and US state-specific emission profiles and their impact on mid-century global warming under different CH _4 mitigation scenarios were conducted. It was found that the climate benefit of natural gas pyrolysis is highly dependent on plant location and the speed at which CH _4 emissions can be abated. New York, Pennsylvania, and Ohio emerged as the most promising locations. This is because of their projected long reliance on natural gas for power generation, which renders electrolysis using grid electricity less attractive, as well as the relatively low estimate of current CH _4 emissions from the natural gas supply chain. However, without fast action on CH _4 emission mitigation, the climate benefit of natural gas pyrolysis is small or non-existent, irrespective of the plant location. Overall, the uncertainty in the relative climate benefit of natural gas pyrolysis was found to be large; however, this study developed an easy-to-adapt MS Excel/visual basic for applications (VBA) tool that can be updated as soon as more accurate data on CH _4 emissions becomes available. Policymakers, businesspeople, and scholars can use this tool to estimate the climate impact within their own scenarios and locations.
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