Depending on who you ask, methane is either a useful transition fuel to a low-carbon future, or a super polluter. The science of methane says that for natural gas to have a lower climate footprint than other fossil fuels, particularly coal, there can be leakage of no more than 3.2% from end to end. Yet studies across the US show wildly different leakage rates. One of the most influential, by Robert Howarth of Cornell University, puts it at 4.8%, making methane worse for the environment than coal. The EPA tells a different story, and says leakage rates are just 0.93%. All of this really matters for the climate, especially since Russia's invasion of Ukraine. The US has become the world's biggest producer and exporter of natural gas, and hundreds of billions of dollars have been invested globally on the premise that natural gas is a cleaner stop-gap between our fossil present and our low-carbon future. So who's right? And how can we find ways to reduce those methane emissions in either case. Grant Swartzwelder, founder of OTA Environmental Solutions and ESG Dynamics, based in Dallas, Texas, joins Cleaning Up to tease out the problem.

Episode Update (Dec 2024)

The 3.2% figure refers to the relative warming impact of coal-fired power generation versus national gas with a given level of leakage on day one - when all of the methane is still in the atmosphere. As methane decays in the atmosphere faster than CO2 is absorbed, the “breakeven” level of fugitive emissions increases as you look at longer periods. If you take the standard 100-year warming period, fugitive emissions from natural gas would need to be around 8% - well above those measured in the US – for gas power to be as bad as coal power. At 20 years the figure is around 4%. (source: https://www.pnas.org/doi/10.1073/pnas.1202407109)
The 4.8% figure has been modified by Professor Howarth subsequent to the release of the episode, based on critiques received when it was in pre-print. Criticism continues, however, and one proposed corrected analysis shows that 100-year GHG intensity of LNG that are at most 15% below the lowest general estimates for coal-fired power. (source: https://thebreakthrough.org/issues/energy/a-major-paper-on-liquified-natural-gas-emissions-is-riddled-with-errors)

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