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What if airplanes only emitted water?
Green hydrogen can absolutely replace jet fuel. It will take will and logistics, and this week, I'm talking to the company that's working on the logistics part.
And before you spin up ANY of your “that’s not possible” or “it’s never going to happen” engines, no pun intended, watch the following. This is the first test flight of a regional jet powered primarily by green hydrogen, conducted in March of this year by Universal Hydrogen. It’s a good one. It’s kind of a weeper if you’re into that kind of thing. The hydrogen-powered engine emits only water as a byproduct, and the hydrogen itself was created using only renewable energy (hence “green hydrogen.”)
So, here’s the deal with airplanes. They emit about a billion tons of carbon dioxide every single year. That’s about 2.4 percent of total CO2 emissions (or 2.6 percent, according to Project Drawdown), and carbon dioxide lingers in the atmosphere and warms the planet for thousands of years. So that’s reason enough to try to abate emissions from flying.
But there’s more! I actually just learned this: the ethereal white contrails streaking out behind your plane are actually also icy clouds of death that trap heat instead of reflecting it the way regular clouds do. In fact, a 2011 study said the contrails alone have led to more warming than all of aviation’s CO2 emissions, ever.
So when you take the contrails into account, air travel’s climate impact becomes more like 3.5 percent of global warming, the vast majority of which comes from passenger travel. And passenger travel just keeps growing—Eremenko told me that in fact, “the industry is built around this inviolate law almost … that traffic doubles every 15 years.”
So there’s a lot of attention on air travel, and trying to figure out how to decarbonize it. It’s a tricky one. Batteries don’t really work because there isn’t enough range and they weigh too much.
Then there are so-called SAFs, sustainable aviation fuels, which are in various stages of development, few of which are very far along. Currently, SAFs make up less than 1% of total aviation fuel, they’re still carbon-intensive to produce, and the biofuels the Department of Energy is so excited about have a strong whiff of ethanol about them. You know, ethanol, the supposedly more environmentally fuel derived from corn that’s mixed in with gasoline at the pump? Turns out, it’s mostly just been a massive subsidy scheme for farmers that, while it may have kept some in business, contributed to massive amounts of mono-crop planting and ended up being up to 24% more carbon-intensive than gasoline.
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Toward the end of this week’s episode, Eremenko has a nice dissection of why, for example, creating enough algae-based SAFs to actually power the entire aviation industry would require covering the entire Mediterranean Sea with algae—which is likely to cause some other problems. Also, creating synthetic jet fuel requires first creating green hydrogen, and then doing a whole bunch of other work to turn it into something closer to kerosene, burning that and creating various planet-warming emissions, but offsetting it by capturing some amount of carbon from the air (which also requires energy).
So yeah, one way to cut air travel emissions is to make flying 8x the cost. That’ll reduce demand, for sure.
So. Back to green hydrogen. First, another explainer. Hydrogen is star food and the most common element in the universe, but here on Earth, we have to make it by splitting it apart from compounds that contain it. This requires energy, and it happens in all kinds of ways that have somehow become part of a little hydrogen color wheel.
For our purposes, the colors to pay attention to are pink and green. Both produce hydrogen through a process called electrolysis, in which water molecules (you know, H2O), are split into oxygen and hydrogen. You vent the oxygen, which harms no one, and you keep the hydrogen. If you do this using renewable energy and you create a zero-emission fuel source, you’ve got green hydrogen, which is a genuinely sustainable fuel solution. If you do this using nuclear energy, you have a zero-carbon solution (pink hydrogen) with some nuclear baggage attached (that’s for a future episode).
And, Eremenko told me, the thing that’s great about hydrogen for powering airplanes and rockets is that even though, yes, it requires energy to produce, it’s an incredibly weight-efficient way to store and release energy—much more so than kerosene jet fuel and more than anything else other than nuclear energy. So while hydrogen might not be the perfect solution for passenger transport compared to electric vehicles (up for debate, I’m sure), it’s perfect for aviation and space travel.
Also, renewable energy is expanding a lot faster than algae farms in the Mediterranean, and electrolyzers aren’t that expensive to build, so green hydrogen has the potential to be and in some cases already is cost-competitive with jet fuel.
(If you’re really down this rabbit hole, here’s a whole long history about how the aviation industry has been experimenting with hydrogen fuel sources since something like the 1930s.)
But the other big knock on hydrogen comes down to, basically, gas stations. Right now, for example, there are hydrogen-fueled cars on the road, like the Toyota Mirai, and there are a grand total of 59 refueling stations in the entire country.
Imagine how much it would cost to replace or supplement the literally trillions of dollars of infrastructure that currently exists for refueling airplanes? To this, Paul Eremenko says, yeah. No. We’re just not going to do that.
So, Universal Hydrogen is a company with two parts—like H2O, if you will. (Sorry.) First, the company makes a conversion kit for the ATR-72, which is a regional turbo-prop jet that does lots and lots and lots of short-haul trips all over the world, so those planes can be fueled by the company’s hydrogen fuel cells.
Second, it makes Nespresso pods.
Ok, not literally Nespresso pods. But that’s the model; the idea is to retrofit planes to take a standard-sized hydrogen-storage capsule, which Universal Hydrogen also makes, that can be stacked and shipped like any old shipping container, and sent anywhere in the world using all the existing delivery networks that criss-cross the globe today. So never mind building hydrogen refueling stations; when you get where you’re going, you just pop in a pod, and the old one gets refilled and re-used (in that way, a quite crucial difference from Nespresso pods, in fact).
The hope, Eremenko told me, is that future planes from Boeing or Airbus or whoever’s prepared to make the leap in the future, will be designed to take these pods, and, as the former chief technology officer at Airbus, he assures me this does not require a massive redesign of airplanes. It just takes will. Here’s what he said:
I think that there's a mindset issue in aviation. You know, the industry has been a victim of its own success. We've basically had incremental evolution of airplane design since the birth of the jet age. And so the industry, the DNA, the muscle memory, right? Nobody knows how to do anything beyond incrementalism in the industry anymore.
Every airplane is a successive, small improvement on the previous. I mean, this is why Boeing has been torturing the 737 since what, the 1960s … when the first 737 came out, and they've had a dozen of derivative variants since then and haven't launched any new planes.
And ultimately the 737 Max was one torture too far … that unfortunately led to several accidents. Which were directly attributable to the fact that they were modifying the design in ways that the original design wasn't meant to be modified.
So, I think that the industry, the aviation industry in particular … are victims to this incrementalist mindset. And we gotta break out of it because this will be different. It's not a huge change … but there is engineering needed … and there needs to be some bravery and some intestinal fortitude from the leadership of the industry.
So what gets us to that bravery?
Well, as in all things, probably economics. If SAFs are 3 to 8 times the cost of jet fuel, that’s a nonstarter. France is banning some short-haul flights over carbon emissions. Flight taxes, carbon taxes, flight shaming, governments limiting air travel to reduce emissions—all of these are possible as global warming inexorably gets worse, and airlines will have to find solutions or face serious revenue pressure.
And not for nothing, but the Inflation Reduction Act includes big subsidies for clean hydrogen production (ok yes, in addition to some SAF research, too).
So we’ll see. The future is not yet written. But as I said in the podcast this week, the main thing I want you to take away is that this is possible. Planes could emit nothing but water. That could happen. They could create gardens on landing instead of contributing to the air pollution that kills 7 million people a year, if not more And they could be quieter, too—much quieter.
The existence of technology does not guarantee the bravery and intestinal fortitude it takes to adopt that technology. But where we can encourage bravery, we should. I want quiet skies and a gentle mist and guilt-free trips to see my family or go on vacation or visit cool conferences. Let’s make it happen, people!
See you next week.