No, that is factually incorrect, hydrogen is not an "extremely potent" greenhouse gas in this context.
Hydrogen has a GWP of 11, meaning it is 11 times worse than emitting CO2. Methane, for example, has a GWP of 34, which is starting to get kind of bad, but "extremely potent" is something like SF6 wich has a GWP of 22800.
Furthermore, GWP is calculated on a mass basis, which skews things a lot for a light molecule like hydrogen.
I'm kind of astonished at the fear mongering on this issue, because it means people cannot be arsed to spend 20 minutes on Google with a calculator to check the numbers before they spread something as a truth. Let's do the actual math.
If you look at a Toyota Mirai, it needs 5 kg of hydrogen to get a 300 mile range. A comparable diesel car needs 28 kg diesel to get that range, and will emit 88 kg of CO2 when that diesel is burned (the O's in CO2 comes from the air).
Even if the hydrogen car had an absurdly high leakage rate of 50% during that trip and the period it stood still before next trip, it would still emit only the equivalent of 27.5 kg of CO2. So at insanely high leakage rate, diesel is still 3x worse than hydrogen.
If we are realistic about leakage rate, published numbers from actual measurements with the Toyota Mirai placed in a sealed container gives us 2 mL/min at 1 bar, so the time to leak the entire contents of the tank is more than 3000 days.
So let's say this is a hobby vehicle (like a small aircraft) seeing infrequent use, you consume two tanks of hydrogen per month. That puts your leakage rate at 0.5%, giving an emissions equivalent of 0.56 kg CO2, while the diesel (avgas) powered equivalent would emit 166 kg CO2 - 300x worse.
Note that this is all based on technology that is already here - you can go buy it today - not some hypothetical developments.
We should do both. Both hydrogen and battery use an electrified power train, and the hydrogen plane would probably have a small lithium battery anyway.
All I care is that all GHG are accounted thoroughly, including H2 leaks. Then, if at the end we are reducing atmospheric GHG contents at the planned rate, all is fine.
The effective GHG potential is about 200x CO2. All of that, short of 6x direct effect, is secondary effects, e.g. scavenging the stuff that removes CH4 from that atmosphere.
It is not at all hard to look this up.
But it doesn't matter very much for aviation; you make it on the spot, put it in, take off, and burn it all before it gets a chance to leak. LH2 does not seep through everything like gaseous H2. It's cold. It freezes stuff it touches, too.
Please don't say CH4 is "kind of bad". It's an atrocious threat for the planet (and Humanity) right now (thawing of permafrost and of oceanic floor, etc).
Be it 11x more potent that CO2 or just 1x, it's completely enough that H2 has a GHG effect, and that H2 leaks are impossible to prevent due to the size of the molecule.
For me, that's enough to make it less desirable than batteries, especially if we are speaking of policies of mass investment on a planet scale!!!
Also, you use a leakage at 1bar then you transpose it to a plane which would obviously not transport the H2 at 1bar but at a much higher pressure.
Finally, if it is not zero-carbon, then it is not. Even "a little" is not zero.
We need to account for it, and never put ZERO on this CO2e accounting line, that's all.
Oh I agree that methane is a horrible threat if it is released at massive scale, like from the permafrost. We should absolutely do everything we can to avoid that.
My point is that if you compare hydrogen on propulsion equivalent basis and with realistic leakage rates, it is so much better than today's solutions that we should absolutely use it.
When it comes to batteries, yeah, that's just not going to happen for anything over 20 passengers and 200 mile operating range. It's physically impossible to obtain sufficient Wh/kg to run even a small airliner on batteries. Airbus is investing heavily in liquid hydrogen fuelled jets, and it's not because they are stupid.
> Also, you use a leakage at 1bar then you transpose it to a plane which would obviously not transport the H2 at 1bar but at a much higher pressure.
So this part was probably too brief in my first post to be perfectly clear. Imagine that you have the 700 bar pressure tank of the Toyota Mirai, and the entire leakage out to 1 bar (the atmosphere) happens in a single point. Then you put a ballon over that point and measure how quickly it grows. That rate is reported as "2 mL/min at 1 bar".
Ok, thanks for the clarification about the calculation. (I should have seen that, as a gas stored at 1 bar will not pour out of its container very well)
That is fine to employ H2 technology if all is accounted for and the leaks are included in the big picture (at consumer end-points as well as producer end-points).
Because, as a reminder, about emissions, we do not only need to "do a lot better" than now, we need to do zero (scratch that, we need to do negative).
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As an aside:
> Airbus is investing heavily in liquid hydrogen fuelled jets, and it's not because they are stupid.
Well, I would not use that as an argument. For example Toyota invested a lot in the wrong direction (and now they cling on their hybrid vehicles even if it makes no sense). (Even worse, see the diesielgate with Volkswagen. Huge corporations can do stupid things)
Hydrogen has a GWP of 11, meaning it is 11 times worse than emitting CO2. Methane, for example, has a GWP of 34, which is starting to get kind of bad, but "extremely potent" is something like SF6 wich has a GWP of 22800.
Furthermore, GWP is calculated on a mass basis, which skews things a lot for a light molecule like hydrogen.
I'm kind of astonished at the fear mongering on this issue, because it means people cannot be arsed to spend 20 minutes on Google with a calculator to check the numbers before they spread something as a truth. Let's do the actual math.
If you look at a Toyota Mirai, it needs 5 kg of hydrogen to get a 300 mile range. A comparable diesel car needs 28 kg diesel to get that range, and will emit 88 kg of CO2 when that diesel is burned (the O's in CO2 comes from the air).
Even if the hydrogen car had an absurdly high leakage rate of 50% during that trip and the period it stood still before next trip, it would still emit only the equivalent of 27.5 kg of CO2. So at insanely high leakage rate, diesel is still 3x worse than hydrogen.
If we are realistic about leakage rate, published numbers from actual measurements with the Toyota Mirai placed in a sealed container gives us 2 mL/min at 1 bar, so the time to leak the entire contents of the tank is more than 3000 days.
So let's say this is a hobby vehicle (like a small aircraft) seeing infrequent use, you consume two tanks of hydrogen per month. That puts your leakage rate at 0.5%, giving an emissions equivalent of 0.56 kg CO2, while the diesel (avgas) powered equivalent would emit 166 kg CO2 - 300x worse.
Note that this is all based on technology that is already here - you can go buy it today - not some hypothetical developments.