From spray-on insulation for tents in Afghanistan to solar-powered water purification systems and biofuel for jets, the U.S. military is working on a variety of fronts to reduce its use of fossil fuels.
The Air Force hopes by 2016 to use biofuel blends for half of the aviation fuel it burns. The Army plans to get rid of 4,000 gasoline-powered vehicles and replace them with electric vehicles by 2013. And the Navy is preparing to launch the "Great Green Fleet" in 2016 - an aircraft carrier strike force fueled by nuclear power and alternative fuels.
The world's mightiest military hasn't suddenly become a troop of tree huggers. The main reason to reduce reliance on fossil fuels "is to make us better war fighters," Navy Secretary Ray Mabus said.
Efforts by the three U.S. services to save energy and switch to alternative energy sources won praise from the Pew Research Center, which said April 20 that "the military is, in many respects, leading the way and helping to re-energize America's future."
For the services, though, alternative energy and conservation is more a matter of saving money and lives.
Consider, Mabus said, what it takes to deliver a gallon of gasoline to a Marine unit in Afghanistan. The gas is shipped across the Pacific Ocean, then trucked across Pakistan and into Afghanistan.
"It's very expensive to do that, and very dangerous," Mabus said. It requires Marines, who Mabus oversees, to protect truck convoys, "some of the most dangerous duty that Marines and sailors perform today."
In combat in June 2008, 44 vehicles and 220,000 gallons of fuel were lost in attacks or other events, according to the Pentagon.
Moreover, convoy duty "takes Marines away from what they should be doing," such as fighting or rebuilding Afghanistan, Mabus said.
When the cost of shipping and guarding is included, the cost of delivering gas to a base in Afghanistan is estimated at up to $400 a gallon, according to the Pew Project on National Security, Energy and Climate.
The military is by far the largest U.S. government consumer of energy. The three services burn 330,000 barrels of oil per day, about 300,000 of that in the form of liquid fuels that power ships, aircraft, combat vehicles and forward-deployed generators, the Pew study says.
In addition, the military uses 3.8 billion kilowatt hours of electricity per year to operate its bases and facilities.
The goal is to obtain 25 percent of the military's energy from renewable sources by 2025.
There's an even more ambitious goal for some military bases. The Army, for example, plans to build a 500-megawatt solar power generating plant at Fort Irwin, Calif., that would end the base's dependence on local power supplies, which are vulnerable to interruptions.
Ultimately, Fort Irwin is to become a "net-zero plus" base, meaning that it produces all of the power it needs - and surplus that can be sold to local utilities.
The Army is also working on geothermal energy, on converting biomass to fuel and on improving energy efficiency, Pew reports.
Mabus said the Navy wants half of the energy it uses in 2020 to come from nonfossil sources. And he said the service's fleet of 50,000 noncombat vehicles - trucks and cars used on bases, for example - can be traded in over the next five years for vehicles that don't run on petroleum.
Energy costs the Air Force $10 million a day, and 84 percent of that is spent on jet fuel. Despite cutting energy consumption at facilities by 20 percent, the Air Force's energy costs have tripled as the price of oil has increased, according to Pew. The Air Force is counting on biofuel blends for its aircraft to bring that cost curve under control.
The Navy, too, is turning to biofuels. The Navy flew its "Green Hornet" April 22 on fuel made from camelina, a plant in the mustard family.
Mabus said camelina offers a distinct advantage over corn for producing biofuel. It "can be used in rotation with things like wheat instead of letting the land lie fallow. So it doesn't take food out of the supply chain, but it does provide American farmers with another crop they can grow."