On a US Navy submarine, every breath you inhale has been repeatedly exhaled from the mouths of about 120 other people. This isn't as suffocating, or gross, as it sounds, because submarines have ventilation systems that take the CO2 out of the air, and recirculate it with chemically catalyzed oxygen.

I take that back, the air is gross, because the chemical used to remove CO2 smells like old diesel mixed with a dash of sulphur, and it permeates everything on board. This chemical, called amine, is known by every submariner (I was one for 3 years), as well as every submariner's wife, husband, or anyone else who encounters that sailor's laundry. However, a new CO2-capturing nanomaterial could bring an end to this most notorious of submarine smells (trust me, there are others).

This is how the CO2-binding molecules coat the sand grain's pores. Look at 'em there, sucking up all that CO2! Pacific Northwest National Laboratory

Unlike amine, which is a liquid, the new material looks like sand. In fact, it is sand, except it is covered with tiny pores, each filled with molecules that selectively pull CO2 out of the airstream. Together, sand grain and molecule are called Self Assembled Monolayers on Mesoporous Supports, or SAMMS. The pores create nooks and crannies that let even a small amount of the material soak up an incredible amount of CO2—a teaspoon of the material has slightly less surface area than a football field. And it's reversible. "With a slight amount of heat, you can also open that molecule back up and release the CO2, making it possible to use the same material over and over again," said Ken Rappe, an engineer at Pacific Northwest National Laboratory who worked on SAMMS.

There are many different types of SAMMS, each designed to bind with a specific molecule. They were originally engineered to pull mercury and other contaminants out of industrial waste streams, Rappe says. The CO2-binding version was identified by accident over a decade ago, when a scientist accidentally dropped a sample of the stuff in a glass of water. The sample started fizzing. Some experiments showed that this fizzing was the water dissolving stored carbon. At the time, carbon capture and storage wasn't a huge research interest (besides, SAMMS likes its CO2 cool, and coal power emissions or automobile exhausts are too hot to capture), and the researchers searched for an application before a colleague pointed them to the problem of funky sub air.

Amine doesn't just stink, it's also highly corrosive and will ruin anything not made of stainless steel. This makes it a huge maintenance burden, as it needs to be flushed and moved into storage whenever it gets saturated with CO2. The sandy SAMMS would alleviate this, as it doesn't need special storage. "When you go from a liquid to a solid, you're able to get rid of all the pumps and tanks," said Jay Smith, an engineer at the Naval Ships Engineering Station, Naval Surface Warfare Center Carderock Division (NAVSSES) in Philadelphia who has been getting the SAMMS-based replacement ready for deployment. "It's also safer, and more environmentally friendly to dispose of," she said.

Changing out life support equipment on a submarine isn't trivial (no matter how reviled the piece of equipment). Rappe and his research partners spent years improving the material before turning it over to the Navy. Since then, Smith and her colleagues have been testing the prototype SAMMS ventilation system specifically for submarines. She says the prototype is currently going through long-term testing with lab-simulated sub air. It could then be deployed on future submarines joining the fleet. Smith also noted that the SAMMS technology has already been evaluated successfully at sea through small scale test units.

And as long as the Navy's switching out gear on the sub, how about a margarita machine in the crew's mess?