r/science • u/Wagamaga • Aug 06 '20

Chemistry Turning carbon dioxide into liquid fuel. Scientists have discovered a new electrocatalyst that converts carbon dioxide (CO2) and water into ethanol with very high energy efficiency, high selectivity for the desired final product and low cost.

https://www.anl.gov/article/turning-carbon-dioxide-into-liquid-fuel
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u/PronouncedOiler Aug 07 '20

I didn't realize that water dissipated quite that quickly in the atmosphere. I'd be curious about how fast CO2 dissipates in comparison. At any rate, it seems possible that there exists a maximum rate that the Earth can eliminate excess vapor. The relevant question is whether or not a purely hydrogen economy would generate vapor above this rate, and thus accumulate in a similar manner as CO2.

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u/PM_ME_YOUR__BOOTY Aug 08 '20

https://www.theguardian.com/environment/2012/jan/16/greenhouse-gases-remain-air

You can read about the different times of ghg in the atmosphere there. Edit: for CO2 it takes between 20 to 200 years to be absorbed by the ocean, or even longer to dissipate in other ways. If it is absorbed by the ocean, that of course changes the water acidity which brings another load of problems as well.

To the maximum rate that the earth can eliminate vapor: I'm not sure if that exists, all I can say with 100% certainty is that there is a maximum amount of water that can be stored in the atmosphere.

I'd assume that more water vapor would result in more rain/snow but of course I know next to nothing about the topic and from what I read we understand very little so far. Fact is that the increase in temperature is the main factor for the increase in water vapor, which in term increases the temperature and so on.

This means that, in theory, an increase in water vapor alone could also increase the temperature, however, at an industrial scale, condensing a good amount of the produced water vapor and seeping it off should be easily possible. I don't think it is practical for cars that run on H2, however there are roads that let rain water seep through. I'm not sure if Trucks are allowed to drive on those or how expensive they are so I can't speak to that being an easy fix or not.

As you can see I am very far from an expert in that field, however I know the basic truth that it will be easier to deal with water than with CO2 and that H2 is more energy dense than Methane or petrol for example, resulting in fewer emissions that are easier to control. I'd say that is a pretty good start.