A new technology to harvest drinkable water from diesel exhaust could help the U.S. military become more nimble and mobile as it engages in conflicts around the world.
Warfare is hot, dirty, and exhausting work that requires a steady stream of water to slake thirst, prepare meals and maintain healthy hygiene — up to nearly 7 gallons a day per person.
Supplying that water to soldiers increases vulnerability to military personnel and limits the tactical use of field troops, according to researchers at the Department of Energy's Oak Ridge National Laboratory who are developing the new technology.
Their solution is to use the fuel that the military burns to run its tanks, Humvees, generators and other machines that power field operations. When fuel is combusted, it gets oxidized and produces carbon dioxide and water.
"Theoretically, one gallon of diesel should produce one gallon of water," project leader Melanie Debusk explained to me Wednesday. While all of that water isn't recoverable, the system her team is developing should be able to get back between 65 and 85 percent of it.
"Considering how much fuel the military uses in the field that would be a significant contribution to the water issue," she noted.
For example, a Humvee, which has about a 25-gallon tank, could provide enough water for about three soldiers per tank of fuel burned.
Capillary condensation
The concept under development is based on the process known as capillary condensation, which contrasts to thermodynamic condensation — that is cooling the air so that water drops out of it.
"With capillary condensation, we've got tiny capillaries in our porous, tubular inorganic membranes," Debusk said, explaining that the system is like a hollow steel tube with porous walls. Water condenses by capillary action in the pores.
This liquid water is constantly drawn off from the outside of the tube, allowing more water to be condensed from the exhaust passing through the center of the tube.
"Based on the rules of capillary condensation, you should be able to condense more water out at a given temperature compared to if you cooled air directly to that temperature and were relying on thermodynamic condensation," Debusk added.
In addition, capturing water vapor in this way leads to approximately a 100-fold reduction in contaminants in the water because "you are condensing it in these tiny pores and you are displacing it continually," she said.
As a result, the contact time between water soluble gases such as nitrogen dioxide and the condensed water is eliminated.
Water shortage solution?
According to the team, this system is an improvement over an earlier technology proposed to convert diesel exhaust to water that was based on thermodynamic condensation, which was heavy, bulky and consumed too much energy to run heat exchangers.
The U.S. military deemed that system "undeployable," according to the Oak Ridge National Laboratory. The lab is pushing for full-scale development of its system within the next few years. The budget required to do so is about $6 million, according Debusk.
If it works at full scale, maybe this is a solution to help cope with looming water shortages? Feel free to weigh in with your comment below.
More stories on water solutions:
- Turning air into water? Gadget does just that
- Things you didn't know about water
- Re-using 'Graywater:' Next step in conservation
- Experts warn of severe water shortages by 2080
John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).