Before the jet fuel that powers an aircraft’s engines can be burned, it begins its life in the ground as a fossil fuel. But the US military is exploring new ways of producing that fuel, synthetically, and on site, where it needs to be used. They’ve just announced a contract for as much as $65 million to Air Company, a Brooklyn-based company that has developed a synthetic fuel that doesn’t take its starting materials from the ground. 

In announcing the contract, the Department of Defense notes that it has an eye on both security concerns and the environment. Getting airplane fuel where it needs to go, the DoD notes, “often involves a combination of ships, tanker planes, and convoys.” And these same transport mechanisms, the military adds, can “become extremely vulnerable.” 

Here’s how the fuel works, why the military is interested, and what the benefits and drawbacks are of this type of approach. 

The chemistry of synthetic jet fuel 

This DOD initiative is called Project SynCE, which is pronounced “sense,” and clunkily stands for Synthetic Fuel for the Contested Environment. By contested environment, the military is referring to a space, like a battlefield, where a conflict can occur.

The building blocks of the fuel from Air Company involve hydrogen and carbon, and the process demands energy. “We start with renewable electricity,” says Stafford Sheehan, the CTO and co-founder of Air Company. That electricity, he adds, is used “to split water into hydrogen gas and oxygen gas, so we get green hydrogen.” 

But fuel requires carbon, too, so the company needs carbon dioxide to get that element. “For Project SynCE specifically, we’re looking at on-site direct-air capture, or direct ocean-capture technologies,” he says. But more generally, he adds, “We capture carbon dioxide from a variety of sources.” Currently, he notes, their source is CO2 “that was a byproduct of biofuel production.” 

So the recipe’s ingredients call for carbon dioxide, plus the hydrogen that came from water. Those elements are combined in a fixed bed flow reactor, which is “a fancy way of saying a bunch of tubes with catalysts,” or, even more simply, “tubes with rocks in them,” Sheehan says. 

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Jet fuel itself primarily consists of molecules—known as paraffins—made of carbon and hydrogen. For example, some of those paraffins are called normal paraffins, which is a straight line of carbons with hydrogens attached to them. There are also hydrocarbons present called aromatic compounds. 

“You need to have those aromatic compounds in order to make a jet fuel that’s identical to what you get from fossil fuels,” he says, “and it’s very important to be identical to what you get from fossil fuels, because all of the engines are designed to run on what you get from fossil fuels.”  

Okay, enough chemistry. The point is that this fuel is synthetically made, didn’t come out of the ground, and can be a direct substitute for the refined dinosaur juice typically used in aircraft. “You can actually make jet fuel with our process that burns cleaner as well, so it has fewer contrails,” he says. It will still emit carbon when burned, though.

Why the Department of Defense is interested 

This project involves a few government entities, including the Air Force and the Defense Innovation Unit, which acts as a kind of bridge between the military and the commercial sector. So where will they start cooking up this new fuel? “We plan to pair this technology with the other renewable energy projects at several joint bases, which include solar, geothermal, and nuclear,” says Jack Ryan, a project manager for the DIU, via email. “While we can’t share exact locations yet, this project will initially be based in the Continental US and then over time, we expect the decreasing size of the machinery will allow for the system to be modularized and used in operational settings.” 

Having a way to produce fuel in an operational setting, as Ryan describes it, could be helpful in a future conflict, because ground vehicles like tanker trucks can be targets. For example, on April 9, 2004, in Iraq, an attack known as the Good Friday Ambush resulted in multiple deaths; a large US convoy was carrying out an “emergency delivery of jet fuel to the airport” in Baghdad, Iraq, as The Los Angeles Times noted in a lengthy article on the incident in 2007. 

“By developing and deploying on-site fuel production technology, our Joint Force will be more resilient and sustainable,” Ryan says.

[Related: All your burning questions about sustainable aviation fuel, answered]

Nikita Pavlenko, a program lead at the International Council on Clean Transportation, a nonprofit organization, says that he is excited about the news. “It’s also likely something that’s still quite a ways away,” he adds. “Air Company is still in the very, very initial stages of commercialization.” 

These types of fuels, called e-fuels, for electrofuels, don’t come in large amounts, nor cheaply. “I expect that the economics and the availability are going to be big constraints,” he says. “Just based off the underlying costs of green hydrogen [and] CO2, you’re probably going to end up with something much more expensive than conventional fuel.” In terms of how much fuel they’ll be able to make synthetically, Ryan, of the DIU, says, “It will be smaller quantities to begin with, providing resiliency to existing fuel supply and base microgrids,” and then will grow from there. 

[Related: Airbus just flew its biggest plane yet using sustainable aviation fuel]

But these types of fuels do carry environmental benefits, Pavlenko says, although it’s important that the hydrogen they use is created through green means—from renewable energy, for example. The fuel still emits carbon when burned, but the benefits come because the fuel was created by taking carbon dioxide out of the atmosphere in the first place, or preventing it from leaving a smokestack. Even that smokestack scenario is environmentally appealing to Pavlenko, because “you’re just kind of borrowing that CO2 from the atmosphere—just delaying before it goes out in the atmosphere, rather than taking something that’s been underground for millions of years and releasing it.” (One caveat is down the line, there ideally aren’t smokestacks belching carbon dioxide that could be captured in the first place.) 

For its part, the Defense Innovation Unit says that they’re interested in multiple different ways of obtaining the carbon dioxide, but are most enthused about getting it from the air or ocean. That’s because those two methods “serve the dual purpose of drawing down CO2 from the air/water while also providing a feedstock to the synthetic fuel process,” says Matt Palumbo, a project manager with the DIU, via email. Palumbo also notes that he expects this period of the contract to last about two to five years, and thinks the endeavor will continue from there.