As the world invests billions in hydrogen fuel systems, scientists are urging vigilance against leakage, since its release into open air can trigger chemical reactions that significantly warm the atmosphere.
Widely seen as one of the only ways to decarbonize sectors that aren’t easily electrified (like heavy industry and aviation), hydrogen has much to recommend it as a clean fuel—unless it leaks into the air, where three chemical pathways can transform it into an indirect greenhouse gas with 33 times the global warming potential of carbon dioxide over 20 years, writes Bloomberg.
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The first pathway involves hydrogen’s tendency to react with atmospheric hydroxyl (OH), an element which also reacts with methane in a manner that helps remove this dangerous greenhouse gas from the atmosphere. The more hydrogen that leaks into the atmosphere, the less hydroxyl will be available to neutralize the warming effects of methane, which is about 85 times more powerful a warming agent than CO2 over a 20-year span.
The second pathway is hydrogen’s involvement, near ground level, in a chemical chain reaction that produces ozone, another potent greenhouse gas.
Finally, leaked hydrogen that makes it into the stratosphere produces more water vapour, “which has the overall effect of trapping more thermal energy in the atmosphere.”
Most leaked hydrogen would not escape into the air, but would rather be absorbed by microbes in the soil. But any hydrogen that does get airborne can wreak climate havoc, at least in the short term.
And it’s the short term that matters, given the speed with which global temperatures are rising, say climate scientists with the U.S. Environmental Defense Fund (EDF).
“The potency is a lot stronger than people realize,” EDF climate scientist Ilissa Ocko told Bloomberg. “We’re putting this on everyone’s radar now, not to say ‘no’ to hydrogen, but to think about how we deploy it.”
With $8 billion in government funding now up for grabs in the United States alone, the “hydrogen hustle” has a serious head of steam, with U.S. utility companies “announcing more than two dozen hydrogen pilot projects in the last two years,” Bloomberg writes.
Many of the projects involve “blending hydrogen into existing natural gas pipelines, sprawling networks that feed everything from power plants to household stoves,” the news agency notes. It is that inclination—to jerry-rig a new technology into an old system—that worries scientists like Ocko. Hydrogen is a much smaller molecule than methane, and so will be even more likely to slip through any cracks, EDF warns.