Comment by harg | Hacker News Reader

Comment by harg | Hacker News Reader

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H2 may well be a more potent GHG when compared to CO2, but it's tendency to remain in the atmosphere for a long time is a factor than shouldn't be ignored and doesn't seem to be mentioned by your first citation. I.e. H2 may be 16x more potent than CO2 but if it reacts away within hours/days/[<16th of the time that CO2 stays around] then its overall contribution to warming will be less than CO2. (I don't know what this figure is, but I believe Hydrogen is pretty reactive so doesn't tend to stick around that long)

From your second citation:

> The evidence base relating to non-GHG emissions from end-use in heating applications is almost non-existent

It then says that a single study:

> suggests there is potential for up to six times higher point NOx emissions compared with natural gas".

and that it could be significantly reduced with catalytic converters.

The points you raise are not nearly as unequivocal as you make them out to be. I also don't feel like Hydrogen is going to solve all of our problems - it has many problems that needs to be overcome. But it could well play a role in certain areas when it comes to getting off fossil fuels, so studies into more efficient production of it will surely be valuable.

>H2 may well be a more potent GHG when compared to CO2, but it's tendency to remain in the atmosphere for a long time is a factor than shouldn't be ignored and doesn't seem to be mentioned by your first citation. I.e. H2 may be 16x more potent than CO2 but if it reacts away within hours/days/[<16th of the time that CO2 stays around] then its overall contribution to warming will be less than CO2. (I don't know what this figure is, but I believe Hydrogen is pretty reactive so doesn't tend to stick around that long)

Usually these numbers take that in consideration and the two are compared over a certain number of years, i.e. 100 years. A quick Google seems to confirm this, H2 is ~10 more potent than CO2 over 100 years.

Good point

Still.. we're talking about unintentional leaks here. With the alternatives, CO2-emissions is an unavoidable by-product (in theory it can be managed with CCS, but not for transportation)

We should use batteries whenever we can, but seems to me like hydrogen is an essential component of a green, fully carbon neutral economy.

Though I agree with the comment above that it's a bit... misleading.. to call hydrogen the ultimate clean energy. Green hydrogen (do differentiate from hydrogen made from natural gas) is a very good clean energy carrier. That'd be more precise to say.

It's GWP over 100 years. This is stated in the source: "We estimate the hydrogen GWP(100) [ie, over a 100-year period] to be 11 ± 5; a value more than 100% larger than previously published calculations." In the past, I've seen ranges between 4.3 and 5.8 for the GWP over 100 years for hydrogen mentioned in articles.

There are numerous studies on the NOx levels produced by combusting hydrogen in air and they all show levels much higher than those associated with methane (and methane NOx emissions are already recognised to be be health threatening in urban environments) because hydrogen burns at a higher temperature which promotes the formation of nitrogen oxides.

All that may be true, and I'm not disputing any of it. But all energy sources and storage methods have their drawbacks. They're not necessarily a reason to something out. I'm sure Hydrogen will play a role in certain areas (e.g aviation and steel production). The tech is still young so there's bound to be significant developments coming.

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