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CMDR_kamikazze OP t1_iyc5606 wrote

Reply to comment by Helios4242 in People who are promoting hydrogen as a green fuel always forget what water vapor is one of the most powerful greenhouse gases. by CMDR_kamikazze

Indeed, but don't forget more water emissions in the sky means more clouds. If your calculations are correct (which seems like it from my perspective) this means we will effectively double the water vapor emissions from aircraft only. And clouds have a greenhouse effect too, but besides that, they capture the infrared (thermal) energy in the atmosphere in one place and release it in another one, thus moving energy around the globe through weather systems. Additional clouds would mean more energy would be trapped and moved around. That's not as harmless as it may seem, these effects should definitely be researched ahead.

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Helios4242 t1_iyc6bfk wrote

>water vapor emissions from aircraft only.

Which is miniscule compared to the amount already evaporating from oceans. Double of miniscule is still miniscule.

By and large, the relative impact of using hydrocarbons on greenhouse gases is not the water vapor but the carbon dioxide. Eliminating the impact on carbon dioxide while doubling its miniscule impact on water vapor is considered to be a good tradeoff by experts in the field (if of course we could reach low-carbon hydrogen production). There's also less nitrogen oxides and particilates. The water vapor is taken into account. It's just not much to account for.

Secondly, as I mentioned, since water splitting would be done with water that is already part of the water cycle, it's just moving it through the cycle. The same amount of water remains on the Earth's surface. Combustion of a fossil fuel adds water to the Earth's surface from where it was stored as a hydrocarbon.

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CMDR_kamikazze OP t1_iyc6pk1 wrote

>if of course we could reach low-carbon hydrogen production

The biggest culprit of all issues with using hydrogen. The easiest way of producing it isn't much better for the environment than directly burning hydrocarbons. And it's exactly the way big fuel corporations want it.

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Helios4242 t1_iyc71wl wrote

of course, but it's good to have the mechanisms in place to use it if the attempts to produce enough clean electricity bear fruit, alongside improvements to hydrogen production efficiency and usage.

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