06.23.11

Turning Diesel Fuel into Drinking Water

Through the process of capillary condensation, Oak Ridge National Laboratory researchers are able to extract water from exhaust fumes.

"For the first time in my life, I appreciated fully the motion picture cliché of a man on a desert crying, "Water, water."—wrote Corporal Eugene Sledge in "With the Old Breed, at Peleliu and Okinawa," a memoir of his time fighting during World War II in the Pacific.

Click to enlarge photo. Enlarge Photo

Boxes of water being offloaded from the back of a military helicopter into a field with 4 soldiers waiting to unload U.S. Army photo by Pfc. Aubree Rundle/Released

A U.S. Soldier offloads pallets of bottled water, mail and MREs from the back of a CH-47 Chinook helicopter onto a poppy field in an undisclosed area of Afghanistan May 8, 2007, during a resupply mission in Regional Command-South.

Corporal Sledge wrote those lines about his service in "Hell's Cauldron," the desperate battle he and his fellow Marines from 1st Marine Division fought on the Pacific island of Peleliu during World War II. Called "The bitterest battle of the war for the Marines," it was fought in 115-degree heat in full combat gear for several days with no reinforcements or supplies. Even the most basic necessity, water, was scarce…and it was contaminated by oil.

Today's military has also faced many logistical challenges in transporting water to arid areas in Iraq and Afghanistan. On average, a soldier needs 7 gallons of water a day for cooking, bathing and drinking, and so one 25-gallon Humvee water tank provides a day's supply for up to three soldiers. Multiply that 7 gallons per person times the 10 to 15 thousand soldiers in a single division, and you have a sense of the logistical challenge involved.

In fact, at the height of Operation Iraqi Freedom, 130,000 troops consumed more than 45 million 1.5-liter bottles of water per month—enough water to fill 27 Olympic-size swimming pools. At one point, transporting fuel and water to forward deployed units—those operating within the sound, and range, of the enemy's guns—made up 80 percent of Army cargo. Convoys are vulnerable to roadside bombs and other attacks. In an effort to minimize the risk of those supply missions, the Army built seven bottling plants in Iraq and tried to make its bases more fuel-efficient.

Yet even today, convoy missions are often the only way for forward deployed units to receive water. To help overcome the challenge of getting water to troops, researchers at Oak Ridge National Laboratory (ORNL) are developing a method to produce potable (drinkable) water…from diesel fuel.

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A US soldier in the foreground looking over a large cargo truck carrying cases of water U.S. Navy photo by Photographer's Mate 1st Class Arlo K. Abrahamson/Released

U.S. Army soldier in Iraq looks on while a truck loaded with fresh water arrives from Kuwait.

That sounds strange until you look at the science. During combustion, diesel fuel is broken down into carbon dioxide and water. In fact, for a gallon of diesel fuel that is burned, a gallon of water is produced. When that happens, water and carbon dioxide normally go straight into the atmosphere as exhaust, but ORNL scientists found a way to trap that water, and then condense it for use with a device called the Membrane Water Recovery System.

The Membrane Water Recovery System consists of a series of tubular nanoporous membranes—which condenses and purifies the water. The device also uses water's natural strength to move it back into the bottle. Water doesn't look sticky when it is splashing in a pool, but it actually has positive and negative ends, which grab together a bit like tiny magnets. This accounts for surface tension. ORNL scientists used that natural stickiness to pull the water through the pores using a process known as capillary condensation, without taking energy from the engine.

Through capillary condensation, ORNL researchers have been able to recover 65 to 85 percent of the exhaust water at high purity, and they hope to apply it to Humvees, diesel generators and other machines. Since most military bases run on diesel generators, the need to transport water through convoys could be reduced, or even eliminated. That will be a little while yet—ORNL researchers hope to have a functional system for the Army within a few years.

But hopefully one day soldiers will not have to worry about when their next convoy will arrive with a fresh bottle of water, thanks to the scientists at ORNL. This project was funded with seed money from ORNL's Laboratory Directed Research and Development program.

For more information on the efforts at ORNL, please go to http://www.ornl.govExternal link.

And for more information on the Office of Science, please go to: http://www.science.doe.gov/.

Bryan Wheeler is a contributing writer for the Office of Science

Last modified: 3/15/2013 5:23:53 PM