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| Hydrogen gas leaking from pipelines can contribute a small amount to climate change fotokaleinar/Shutterstock |
Hydrogen leaked into the atmosphere from pipes or storage tanks indirectly acts as a greenhouse gas, but there are still significant climate benefits to be had if we switch from burning fossil fuels to burning clean hydrogen.
When burned, hydrogen emits only water vapour and heat. If produced with clean energy, hydrogen fuel offers a carbon-free way to power processes that are difficult to run on electricity, such as steel-making. As such, it is seen as an important part of transitioning away from fossil fuels.
However, if hydrogen leaks into the atmosphere rather than being burned, it contributes indirectly to global warming by reacting with other atmospheric gases. As momentum has grown to use more hydrogen fuel, researchers have paid more attention to this often overlooked problem, says Ilissa Ocko at the Environmental Defense Fund, a US nonprofit.
Keith Shine at the University of Reading in the UK and his colleagues have now compared the climate downsides of hydrogen leaks with the benefits of using hydrogen as an alternative to fossil fuels. They used the latest measure of hydrogen’s warming effect: researchers recently reached consensus that hydrogen has roughly 12 times the warming effect of carbon dioxide when measured over 100 years.
In a scenario where the world uses lots of hydrogen all produced using renewable energy – known as green hydrogen – Shine and his colleagues found that hydrogen leaked while storing, transporting and using the gas would reduce the climate benefits of the switch by only a small amount – between 0.4 and 4 per cent, depending on the leakage rate. “From the climate side, it’s good news,” says Shine.
Ocko says she broadly accepts the conclusions reached by Shine and his colleagues. But she points out that the warming effect from hydrogen leaks is more significant when measured in the short term than when measured over 100 years. This is because the gas doesn’t last very long in the atmosphere, so most of the warming it contributes to happens in a matter of a few years.
There is also uncertainty about the amount of fossil fuel emissions avoided for each kilogram of hydrogen that is burned. In a worse-case version, Ocko says the leakage problem could undo something like 40 per cent of the benefits of using green hydrogen in the near term.
The calculus also changes completely if the hydrogen is made using fossil fuels, as nearly all hydrogen is today. In a study published last year, Ocko and her colleague Steven Hamburg found that even “blue hydrogen”, which is made using natural gas and carbon-capture technology, could actually be worse than the status quo in the near term due to leaks of hydrogen and the methane used to make it.
“We will not get the anticipated climate benefits if we don’t take care of the hydrogen emissions problem,” says Ocko. She says hydrogen leaks could be reduced by using it mainly in well-controlled industrial hubs rather than pumping it into homes or using it in vehicles. Avoiding venting excess hydrogen would also help.
Journal reference:
Atmospheric Chemistry and Physics
DOI: https://doi.org/10.5194/acp-23-13451-2023
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