This startup is about to conduct the biggest real-world test of aluminum as a zero-carbon fuel

The initial pilot will use the engine to supply hot steam and hydrogen. But the energy released in the reactor could be put to use in a variety of ways across a range of temperatures, according to Godart. The hot steam could spin a turbine to produce electricity, or the hydrogen could produce electricity in a fuel cell. By burning the hydrogen within the steam, the engine can produce superheated steam as hot as 1,300 °C, which could be used to generate electricity more efficiently or refine chemicals. Burning the hydrogen alone could generate temperatures of 2,400 °C, hot enough to make steel.

Picking up scrap

Godart says he and his colleagues hope the engine will eventually power many different industrial processes, but the initial target is the aluminum refining and recycling industry itself, as it already handles scrap metal and aluminum oxide supply chains. “Aluminum recyclers are coming to us, asking us to take their aluminum waste that’s difficult to recycle and then turn that into clean heat that they can use to re-melt other aluminum,” he says. “They are begging us to implement this for them.”

Citing nondisclosure agreements, he wouldn’t name any of the companies offering up their unrecyclable aluminum, which he says is something of a “dirty secret” for an industry that’s supposed to be recycling all it collects. But estimates from the International Aluminium Institute, an industry group, suggest that globally a little over 3 million metric tons of aluminum collected for recycling currently goes unrecycled each year; another 9 million metric tons isn’t collected for recycling at all or is incinerated with other waste. Together, that’s a little under a third of the estimated 43 million metric tons of aluminum scrap that currently gets recycled each year.

Even if all that unused scrap was recovered for fuel, it would still supply only a fraction of the overall industrial demand for heat, let alone the overall industrial demand for energy. But the plan isn’t to be limited by available scrap. Eventually, Godart says, the hope is to “recharge” the aluminum hydroxide that comes out of the reactor by using clean electricity to convert it back into aluminum metal and react it again.According to the company’s estimates, this “closed loop” approach could supply all global demand for industrial heat by using and reusing a total of around 300 million metric tons of aluminum—around 4% of Earth’s abundant aluminum reserves.

However, all that recharging would require a lot of energy. “If you’re doing that, is an energy storage technology, not so much an energy providing technology,” says Jeffrey Rissman, who studies industrial decarbonization at Energy Innovation, a think tank in California. As with other forms of energy storage like thermal batteries or green hydrogen, he says, that could still make sense if the fuel can be recharged using low-cost, clean electricity. But that will be increasingly hard to come by amid the scramble for clean power for everything from AI data centers to heat pumps.

Despite these obstacles, Godart is confident his company will find a way to make it work. The existing engine may already be able to squeeze out more power from aluminum than anticipated. “We actually believe this can probably do half a megawatt,” he says. “We haven’t fully throttled it.”

James Dinneen is a science and environmental journalist based in New York City.