Scientists Announce New Method to Pull Potable Water From Tank Exhaust

By Patrick Morgan | April 20, 2011 1:24 pm

What’s the News: Scientists have developed a new process that condenses diesel fuel exhaust into water. If implemented on the battlefield, it would allow soldiers to produce drinkable water from burnt fuel in tanks, generators, and Humvees, freeing them from carrying quite so many heavy water-filled containers. “Theoretically, one gallon of diesel should produce one gallon of water,” project leader Melanie Debusk told MSNBC.

How the Heck:

  • The new process involved is called capillary condensation, and as Debusk told MSNBC, the set-up resembles a “hollow … tube with porous walls.”
  • As the exhaust funnels through an array of porous ceramic tubes, the microscopic pores on the side of the tube condense the water via capillary action.
  • As liquid water is extracted from outside the tube, it frees up room for the pores to fill up again, allowing a person to continue producing water.

What’s the Context:

  • The military has experimented with producing water from exhaust before, but they only tried thermodynamic condensation, wherein you have to cool the exhaust in order to condense it. They ditched this method because the equipment required to cool the exhaust was too bulky and heavy, defeating the purpose of finding a lighter alternative to lugging water.
  • Since the capillaries separate the water from water-soluble gases, the process results in water that’s pure enough that upwards of 85% of it is potable, say the researchers.
  • On average, a U.S. soldier requires seven gallons of water a day. A single Humvee’s 25-gallon gas tank could potentially provide “enough water for about three soldiers per tank of fuel burned.”

The Future Holds: If Debusk’s lab gets a $6 million budget, she says she’d like to develop the system to its full capacity in the “next few years.”

Image: flickr / Nikhil Verma

CATEGORIZED UNDER: Environment, Technology
MORE ABOUT: gadgets, Technology, water
  • Angus

    What the hell is each soldier doing with seven gallons of water a day? A gallon to drink (maybe), a gallon to wash (which doesn’t need to happen every day), and less than a gallon in food. Maybe that should be the priority.

    Also, there’s no way in hell to get a gallon of water out of a gallon of diesel. The very fact that combustion produces by-products other than water (like CO2 and soot) render that impossible.

  • Papabear

    Angus-the soldiers are carrying anywhere from 50-100 lbs of gear and up and often operating in temperatures exceeding 100 degrees. I know from my own experience I had no problem emptying a 3 1/2 gallon water jug when I worked construction in college during the Texas summers. That was only drinking water for a 10 hour shift. I wasn’t wearing body armor, or carrying any gear either. 7 gallons is perfectly reasonable.

  • humble reader

    .

  • humble reader

    @angus – actually one gets about 1.3 gallons of H2O per gallon octane after condensing the product. Cetane/diesel would be expected to yield even more.

  • Daniel J. Andrews

    Some times I think if it wasn’t for the military not a whole lot of conservation-effort related things would get invented. I can see various politicians saying, “Why the hell do we want to spend all that money on making water when we can just turn on the tap?” [/tongue-in-cheek--partially]

  • MT-LA

    I’m wondering about the back-pressure: These tubes would need to be inserted into the exhaust stream and the exhaust would be forced through in order for the water to condense. It effectively puts a throttle point in the exhaust (like a car’s muffler), and this increases back pressure. Any increase in back pressure would drop the power of the engine, thus reducing war-fighting capability.

    I think a little drop in horse power would be a welcome trade off for the ability to produce water on-board. However, it *is* a trade off that should be acknowledged and dealt with.

  • http://DiscoverMagazine Templar 7

    Sounds like whoever is doing the research here is being very broad in their standards of whats “Water”.

  • Brian

    Angus, a gallon is a unit of volume. One gallon of one thing can produce many gallons of other stuff after undergoing a chemical reaction. The total space those atoms and molecules take up can change depending on their new forms.

  • Chemist

    Combustion of a hydrocarbon uses the oxygen in the air to provide the O in H2O. 8/9 of the mass of the water produced is oxygen. Only 1/9 of the mass comes from the fuel. The density is secondary in the calculations. The chemistry we took in school really does apply to the real world.

  • Scientists have developed

    Combustion of a hydrocarbon uses the oxygen in the air to provide the O in H2O. 8/9 of the mass of the water produced is oxygen. Only 1/9 of the mass comes from the fuel. The density is secondary in the calculations. The chemistry we took in school really does apply to the real world.

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    this is nice post

  • Geack

    @ MT-LA -

    You’re basically right, but with two caveats: 1. There’s nothing that states the exhaust in the filter is under any pressure – they might be collecting it into some container and then letting it flow through the filter, or the filter may be sufficiently porous that the backpressure is negligible. 2. “From here on out it’s just engineering” – that line is a running joke with engineers, but there’s truth behind it – once the basic science is worked out, modern engineers are astonishingly good at putting theory into practice. With a tech as well-developed as diesel engines, it’s safe to assume that any problems from added backpressure will be resolved with little difficulty.

  • Geack

    @ Daniel J. Andrews -

    Amazing what can be done with a huge publicly-funded research budget and no political interference. Seems like we ought to try that more often :-)

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