Hydrogen proponents, particularly those who want to sell us on the superiority of hydrogen as a transport fuel for fuel cell electric vehicles, would like us to believe it. But what would it take to make such a dream – the generation of hydrogen from renewable electricity, a reality?
Hydrogen production figures for the world aren’t easy to find. Most of the world’s hydrogen isn’t made as a product and sold. Rather, because hydrogen is so low in density- even as a liquid it’s only 71 kg/m3, and as a gas at 10,000 psig it’s only around 42 kg/m3 – it’s quite the devil to transport. Accordingly, major hydrogen users either build their own hydrogen plant, or build their own facilities next door to a major hydrogen plant that already exists. That makes accounting for H2 production rather more difficult than keeping track of how much gasoline or diesel fuel is used.
The best figures I could find for the breakdown of hydrogen sources are below:
Total: 500 billion standard m3/yr- roughly 42,000 kT/yr
48% from natural gas
30% from “oil”, generally meaning internal use in oil/petrochemical refineries
18% from coal
4% by electrolysis
Of that 4% made by electrolysis, a chunk of it is hydrogen made as a by-product in chlor-alkali manufacture, some of which is used for energy, some of which is used for HCl production. So, the world’s on-purpose hydrogen electrolyser capacity in 2000 was quite a bit less than 4% of world hydrogen production. All the rest is made from fossils and resulted in fossil CO2 emissions to the atmosphere.
To a first approximation, let’s consider the 4% made as a by-product of chlor-alkali to be made with grid average electricity- which in 2018 was about 33% non-fossil/non emitting.
That puts total world hydrogen production at:
96 + 2/3(4) = ~ 98.5% fossil, without carbon capture.
The world’s chlor-alkali plants are likely a little greener than the average grid though, given that these energy-intensive plants, and aluminium smelters too, are often paired with hydro dams. So that figure should be used with caution- though it’s roughly correct.
This report from IRENA has more recent and fairly solid data from IEA:
The IRENA report confirms a ~ 5% figure for by-product hydrogen from chlor-alkali and confirms that almost no hydrogen is currently made from renewable resources. But the amounts of hydrogen used are much, much higher- 120,000 kT (120 megatonnes) per year if you include the hydrogen in syngas used to make methanol, hydrogen used in refineries etc.
Note that in 2019, virtually no hydrogen was used to power vehicles. About 40 MT of H2 was used in refineries- there isn’t data as to how much of that was produced from refinery waste streams. At least 1/4 of that, or 10 MT, would still be required even if we swore off the burning of fossil fuels entirely, because we would still need H2 to desulphurize petroleum used in making chemicals, plastics etc.- things we’ll still use petroleum for even once we’ve (hopefully) stopped wasting it for its lowest value use to humankind- as a fuel.
Let’s do a simple calculation to put the current hydrogen use in perspective. Let’s take the 40,000 kT of non-fossil pure H2 production in 2000 (i.e. 1/3 of the total reported by IRENA for 2019), and assume we wanted to make that today using a 70% efficient PEM electrolyser- 70% on a lower heating value basis i.e. relative to 33 kWh/kg of useful energy in hydrogen.
Relative to the higher heating value which includes the heat of condensation of the product water, which is more commonly used to make electrolyser efficiencies sound good, that’s over 83% efficiency- more or less the system efficiency state of the art at present. Cheaper alkaline electrolysers run about 55% efficient on an LHV basis, for the whole system, based on quotations I’ve received for pilot plant projects. So: taking a 70% LHV efficiency, we’d need at least 47 kWh of electricity fed to make a kg of hydrogen. Storage? That’s extra- storage at 700 bar, common for transport applications, takes at least another 10%. Let’s ignore storage, and grid losses, for the moment just to keep things simple:
40,000 kT/yr H2 x 47 kWh/kg with unit conversions works out to about 1880 TWh/yr.
For reference, the 2016 worldwide non-hydro renewable electricity production was about 2000 TWh (per the IEA, 2018- 8% of world production of 24,973 TWh).
If we devoted 100% of the solar panels, wind farms and geothermal generators which existed in 2016, to producing nothing but hydrogen- and we had the hydrogen electrolyser capacity to do that- we could have made the amount of hydrogen we were using in the world in 2000 as pure hydrogen, with a tiny bit to spare- not quite enough to store the resulting hydrogen as a high-pressure gas.
We’d only manage to make 1/3 of the total amount of hydrogen we used in 2019. That’s using all the wind and solar we generated in 2016.
To make 40,000 kT/yr of H2 would take a continuous 24/7 electrolyser capacity of about 214 GW. However, renewables such as wind and solar are intermittent. Taking an availability factor of say 33% as an average of wind and solar, that’s around 650 GW of electrolysers required to replace the fossil hydrogen we used in the year 2000. For reference a 1.5 MW PEM electrolyser sold by Hydrogenics fits inside a standard 40-foot shipping container. So, we’d need 434,000 shipping containers worth of electrolysers, to a first guess, to replace the fossil pure H2 production in the year 2000.
We can certainly quibble about some of my assumptions- these are low precision estimates for sure. Someday the electrolyser efficiency might get to 80%, and maybe the availability of renewables will increase to 45% if we build more offshore wind and less solar. But the conclusion is still the same: just replacing the H2 we’re making from fossils – much less also replacing gasoline and/or diesel with hydrogen – is a positively staggering task.
And that’s a disaster really, because if we want to curtail fossil CO2 emissions, we’ll need to make ammonia, urea and nitrate from renewable rather than fossil hydrogen – the alternative is to give up eating, as the mass agriculture which actually feeds the human and food animal population is very dependent on these sources of nitrogen fertilizer. Ammonia and its derivatives are a huge user of (fossil) hydrogen and are responsible for something around 2% of global fossil GHG emissions right now. Nowhere nearly as bad as transport, or even electricity generation from fossils today- but still a very substantial problem.
This article focusing on Dutch hydrogen production does a very thorough job of looking at the economics of hydrogen production from renewable electricity as a way to store the value of renewable electricity which might otherwise be curtailed. To paraphrase, the author says,
Sure, we can- we’re doing it now. But if we want to make hydrogen from fossils without emitting fossil GHGs to the atmosphere, not only do we have to be very careful about methane leakage (most H2 is made from fossil methane), but we also must consider what to do with that CO2. There is, in theory, sufficient deep saline aquifer capacity to stuff all that CO2 into, and about 2/3 of the CO2 produced by a steam methane reformer is at pressure and hence fairly easy to separate out for sequestration. But of course, stuffing CO2 into the subsurface takes two things in abundance: energy, and money for high pressure compressors and injection wells and pipelines. Right now, the big use for CO2 collected from burning fossils is to get more fossils out of the ground by means of enhanced oil recovery (EOR). Is that helping? It is, when it offsets the mining of natural CO2 for the same purpose- but it does ultimately result in even more fossil CO2 in the atmosphere.
There’s another way: it is possible by a variety of means to convert methane not to CO2 and H2, but rather to H2 and carbon. Monolith Materials is doing this right now, and it’s a spectacularly good idea as a way to make carbon black- useful in all sorts of applications- while also making hydrogen.
Of course, Monolith would freely admit that if they had to bury their carbon black instead of selling it as their primary product, they could never make a business out of selling just the resulting fossil CO2 emission-free hydrogen.
Other firms are planning to do the same with graphite being the desired product.
A little math here is very instructive. Let’s say 60 megatonnes per year of H2 are still needed after we stop fossil burning deliberately, i.e. 1/2 of how much we use today. If we were to find a magical way to do endothermic pyrolysis of methane without spending any energy- i.e. this is impossibly optimistic- then we’d need to use 60 *16/4 = 240 megatonnes of methane and produce 180 megatonnes of carbon per year. For reference, the world markets for carbon black and graphite are 14 and 1.5 megatonnes per year total. We’d be making, and burying at cost, rather than using, an awful lot of artificial coal if that was our intended way to make hydrogen!
All in all, methane pyrolysis, done right, is a nice but very partial solution- one which might make money making a product with the production of non-emitting hydrogen being feasible. But it’s not a scalable solution to be a significant source of non-emitting H2 relative to how much we use now or might use in the future once we stop burning fossils as fuels- much less for new inefficient uses.
There are other good ideas out there. We can make some hydrogen by gasifying biomass, or by reforming methane produced from waste biomass by anaerobic digestion. It is a little challenging and fairly lossy, as H2 for fuel cells needs to be very pure- less than 10 ppm total in CO and CO2, which is a stretch when you’re starting with a biogas stream which is 500,000 ppm CO2. Using biomass will help reduce the challenge of de-fossilizing H2 production. In fact, reforming biogas is cheaper right now than electrolysers as a source of renewable hydrogen, and hence that is apparently the major source currently of the 1/3 of hydrogen for use in fuel cell vehicle refuelling in California by mandate. The other 2/3 of FCEV refuelling H2 is made from fossils and is much cheaper- even though California has a modest carbon pricing scheme. Retail, California H2 is $15/kg – $75 to drive a Toyota Mirai 320 miles. Not a cheap fuel…
Beware the lure of biomass, however. Biomass-derived fuels are again, a nice but very partial solution if done right, and a source of environmental and social harm if done wrong. And when they are used, using them directly as fuels makes more sense than converting part of their energy to another fuel unless that is necessary. One place this is necessary is to fuel jet aircraft. Hydrogen is possible for that purpose but is a very impractical option for a mode of transport that really cares about energy density per unit weight and volume because it must push that volume through the air at high speed.
I’ll leave you with this caution: these facts aren’t, or shouldn’t be, unknown to even the most ardent fuel cell vehicle supporter. They tend to heap on the criticism of battery electric vehicles because we still make a lot of our electricity worldwide from fossils too. However, the proportion of electricity made by low GHG emission sources is positively HUGE compared to the proportion of hydrogen production from non-emitting resources right now. And because battery electric vehicles are over 3x as energy efficient as FCEVs, using that electricity directly rather than indirectly via the lossy hydrogen middleman will mean that the challenge of building out renewable generation capacity will be 1/3 as great if we go this route for cars and light trucks- where batteries are a fully feasible alternative to hydrogen.
Consider the possibility that something else is going on: since hydrogen right now is overwhelmingly made from fossils, is it likely that fuel cell vehicles would be fuelled with renewable hydrogen? Or is this a “bait and switch” scam to sell you fossil fuels in another form? Some H2 advocates are more honest about this than others.
Want to receive exclusive content? Sign up through the short form below.