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Dear Dot,
I keep hearing about hydrogen power and don’t know much about it. Do you? Is it really green?
– Elaine
The Short Answer: Hydrogen is the most abundant element on Earth and often hailed as a clean energy champ (frequently by oil and gas companies eager to piggyback on their existing infrastructure). But there’s no simple source of pure hydrogen; we must manufacture it — and how we do that determines just how low-emissions it is. Logistical challenges get in the way, and, experts say, economics is also discouraging widespread adoption of hydrogen. Solar, wind, and batteries are cheaper for now, and thus leading the way.
Dear Elaine,
Thanks to your question, you can move Dot from the “no, I don’t know much about hydrogen power at all” group to the one that answers, “why yes, I do know a thing or two about hydrogen power.” Let me share my newfound knowledge with you. Because you’re right, Elaine. There has been plenty of chatter about hydrogen as a clean energy source. But is it? Really?
Dot took your question to the brainiacs at the Massachusetts Institute of Technology where Dr. Ruaridh Macdonald, the Energy Systems Research Lead at the MIT Energy Initiative, was delighted to share his research about how to decarbonize the electricity grid while ensuring grid resilience and security.
Hydrogen can be a “clean” energy source, he told me, although that “can” is doing some heavy lifting. It all depends on how hydrogen is produced. If it’s produced, which it often is, by subjecting natural gas (or sometimes coal) to intense conditions that “crack” it into carbon and hydrogen, you will get your hydrogen with a side (or main!) of carbon dioxide. But if instead you use electricity to split water molecules (H₂0, as you might recall from your high school chemistry class) into hydrogen and water, and that electricity comes from a source with low emissions (think wind, solar, or nuclear energy), then the hydrogen is also considered clean. And when it’s burned, hydrogen produces only water vapor, making the entire cycle low-emission.
But let’s not get too excited about green hydrogen, Dr. Macdonald warns. “The vast, vast majority of hydrogen today is not clean. It’s made from natural gas, often coal.” (And let’s remember that even though natural gas is routinely marketed as a clean energy source, that’s just greenwashing at work.)
The thing is, hydrogen is a really useful chemical, he says, explaining something that sounds important about hydrogen being at one end of the periodic table. Dr. Macdonald perhaps senses from my silence that, as far as chemistry goes, I am a Dot of Very Little Brain (to quote my favorite Bear), or at the very least a Dot who has long forgotten her periodic table along with any rationale for knowing it in the first place, and so he says summarily that “it’s just very useful chemically.”
In what way? I ask. Nitrogen and hydrogen combine with a catalyst to produce ammonia, he tells me, which is used for fertilizer.
(There is research into this low-emissions method of creating hydrogen for a “decarbonized” fertilizer.)
So, hydrogen coming from natural gas is not green, but hydrogen produced using clean energy to split molecules is. And here’s where hydrogen’s eco-benefits become clearer: Storing and transporting energy to meet demand (including energy from wind and solar) requires batteries or fuel cells (which store hydrogen); as fuel cells are growing more efficient, people are taking another look at hydrogen. “This is going to be a serious question of, we can build a lot of renewables and we’re going to need a lot of long duration storage,” Dr. Macdonald says. “Hydrogen is a chemical that people sort of understand what it looks like when you move it across the country in pipelines or trucks, and so it would seem a good option.” What’s more, he says, with a bit of modification, our existing infrastructure, such as natural gas turbines, could work with hydrogen, which further increases its attractiveness as an alternate energy source. (Although the idea of using existing gas infrastructure for hydrogen is a pipedream, according to some.)
Dr. Macdonald pauses. “There’s a ‘but’ coming,” he tells me. I suspect I know where he’s going with this. And, readers, perhaps you, too, can conjure memories of that ‘but.”
While people think of gasoline as flammable, Dr. Macdonald continues, even two cars hitting each other isn’t likely to cause gasoline to catch fire. Hydrogen, however, is a bit more … combustible.
Another concern is storage, which is tricky, Dr. Macdonald explains, “because you typically have to compress the hydrogen quite a lot, and you also might have to keep it quite cold.” Which means you need a refrigerator and a fairly thick storage container. “And if that storage container were to get into a car accident, even if it doesn’t set on fire, you might rupture the tank, and then you get a separate rush and a mini explosion of the hydrogen when it all escapes.” In short, a mini Hindenburg.
But what, then, about all those city buses that boast they’re powered by hydrogen?
“So, hydrogen is very good on a weight basis, but it's pretty bad on the volume basis, in the sense that a kilo of hydrogen is a lot of fuel, but it takes up a huge amount of space relative to a kilo of gasoline,” he says. Put another way, hydrogen “really favors working in big systems.” Like a bus. Batteries, on the other hand, are good on a space basis, but they’re really not that great from a weight basis. “So they don't do so well for really big trucks and buses.” Consequently, he says, we’re seeing this split where heavy-duty vehicles might favor using hydrogen (this truck managed to go 1,800 miles without refuelling — hydrogen fuel cells are quite efficient, confirms Dr. Macdonald), while light-duty vehicles stick to batteries.
But, again, let’s remember that hydrogen is only “green” if it relies on clean electricity to split molecules.
Even then, however, hydrogen is losing ground to solar, wind, and batteries on economic grounds, writes Bill McKibben in his The Crucial Years newsletter. “Australia was one of the countries planning on producing lots of ‘green hydrogen,’ using abundant renewable electricity supplies to create the fuel,” he wrote. “But that bubble appears to be bursting — in large measure because the economic argument doesn’t make much sense as solar, wind, and batteries just keep getting cheaper.”
Blue hydrogen, which you might have also heard about, Elaine, is “hydrogen made from fossil gas, but with two sets of carbon capture equipment added to it,” McKibben tells us, citing a Stanford paper that nevertheless concludes that, even in the best-case scenario, “We see no way that blue hydrogen can be considered ‘green,’” a conclusion reached at least in part because carbon capture that proponents suggest could be stored indefinitely is “optimistic and unproven.”
Joe Romm, climate scientist and author of The Hype About Hydrogen (available on Amazon and Bookshop), calls it the “hydrogen mirage,” in an interview with Clean Technica, noting that “Part of the resurgence of interest in oil and gas companies is because they’re the ones who know how to use hydrogen. … I’ve always felt the reason they pushed it so hard is that they never believed green hydrogen would be cost-effective. They assumed people would eventually come running back to them to make it from methane — with promises to capture some carbon along the way. And they were right.” As long as green hydrogen isn’t cost-effective, it will be made from methane, he says.
So there you have it, Elaine. Like so many climate “solutions,” you need to look carefully. Can hydrogen be a clean energy source? Yes. And there are applications, such as buses, where we’re already seeing it being used. But logistics (storage/transport) and cost are, so far, discouraging widespread adoption.
Combustibly,
Dot
