hydrogen, page-43

I would like to point out that the idea that hydrogen has no downsides is not necessarily true. As many folks may know, methane is a more potent greenhouse gas than carbon dioxide but is not a long-term threat as it has a very short atmospheric lifetime compared to CO2. This is because it is destroyed in the atmosphere when reacting with the hydroxyl radical. It's why the lifetime of methane in the atmosphere is typically given as around 12 years.

The problem is that hydrogen also competes for the hydroxyl radical in the atmosphere in a reaction that forms water so more hydrogen equals less methane removal and thus a longer atmospheric lifetime for methane. Because hydrogen so easily escapes containment, a lot could be inadvertently released into the atmosphere as the hydrogen economy grows and that could have a major effect on how long methane lingers and how much builds up in the atmosphere.

So it will be important for a hydrogen economy to be accompanied by a reduction in methane emissions. Roughly half of methane emmisions come from human sources and those emissions can be reduced by mitigating natural gas leaks in infrastructure and the reduction of rotting plan matter in landfills, and burping cows.

But natural emissions have been rising, specifically from wetlands, with a big part coming from tropical wetlands, especially in Africa. The problem is that if these sources are mitigated, it would result in more CO2 in the atmosphere because they are large carbon sinks. So it's a very complicated issue where there is no single golden bullet. It all has to work in tandem and unless temperatures start falling dramatically very soon, we could see a higher percentage natural methane released, which would exacerbate the issue with hydrogen.