Army Scientists Put the “Pee” in Power

By combining urine and aluminum powder, soldiers may be able to produce energy in the field

pee power
The aluminum nano-powder reacts in the lab. David McNally, Army Research Laboratory Public Affairs

When Army scientists mixed some of their new aluminum-based nano-powder in water, the results were startling.

“It bubbled very similarly to an Alka-Seltzer tablet, but probably more violently,” says Kristopher Darling, a materials scientist at the U.S. Army Research Laboratory (ARL) in Maryland.

The scientists realized that the powder was somehow splitting water and releasing hydrogen, an exciting discovery given hydrogen’s usefulness as a fuel. But when they mixed the powder with urine, things got really exciting. The bubbling, already vigorous, became even more lively, suggesting that the powder was extracting more hydrogen from urine than from the water. Later measurements showed the reaction rate was about double.

Why were Army scientists mixing aluminum nano-powder and pee, you might ask? Well, the mission of the laboratory is to develop materials that could one day benefit soldiers in the field.

“How do you supply energy to away teams that are gone for an extended period of time?” Darling asks. “So we began to look at how do you utilize existing fluids that the solider would have on them?”

The team is not yet sure why the aluminum powder produces more hydrogen from urine than from water. It could have something to do with the electrolytes in urine, or differences in the pH. But what they do know is that the ability to produce hydrogen in the field could have dramatic benefits.

“The applications could be anywhere you need power,” says ARL scientist Scott Grendahl.

Soldiers could carry aluminum nano-powder to mix with water or urine to juice up a fuel cell. The powder could be painted on the inside of tanks to, when wetted, provide a power boost when fuel ran out. It could be 3D printed into parts for drones or robots that could “self-cannibalize” when running low on power by dipping themselves in water.

The powder could also potentially be produced in the field through gathering things like aluminum cans and blown-up vehicles. If this were successful, then soldiers in theory could make fuel out of nothing but scavenged materials and their own urine.

This is a big deal, as a large percentage of soldier deaths in the Middle East happen during fuel supply convoys. This fact has given the U.S. military a major incentive to create new, more efficient fuel technologies.

Hydrogen has long been touted as a green fuel. But it’s not simple to transport, as it needs to be either pressurized or liquified first. Producing hydrogen from water using aluminum is not new. But these processes have always needed a catalyst, which traditionally means adding acids, bases or additional energy, or using high temperatures. Some of these catalysts can be toxic and polluting. This new process, by contrast, simply needs the aluminum alloy nano-powder and a water-based liquid—water, sports drink, urine, saliva. The nano-powder is made of tiny grains of aluminum and other metals arranged in a nano-pattern.

“We have no catalyst, our byproducts are inert and nontoxic, and it’s very efficient,” Grendahl says.

The team is currently in the process of patenting their invention. The next steps will be optimizing the process and scaling up. The team can currently make the powder in kilogram quantities, and expects it will be relatively simple and inexpensive to make larger amounts. After that, other ARL teams will get involved to work on applications. There has also been interest from universities and private industry. This isn’t surprising, given how useful on-demand cleanly-produced hydrogen could be for things like hydrogen-powered cars. But, as experts caution, it’s not clear yet how the process will work outside of the lab.

If it’s successful, the soldier of the future may be powering his or her flashlights and communication devices with nothing but empty soda cans and pee. Talk about recycling. 

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