The Armed Forces are going green.

The Army and Air Force are developing technology to turn trash into gas — and therefore cash — for the Department of Defense, the largest consumer of energy in the United States.

According to Pentagon figures, the Defense Department spent $13.6 billion for energy in 2006. It uses 340,000 barrels of oil a day, or 1.5 percent of the total energy consumed in the U.S.

Pentagon officials consider that dependency on oil — much of it produced abroad — not only a huge expense, but a national security risk as well.

The Armed Forces use 1.2 million barrels of oil each month in Iraq alone, and former CIA director James Woolsey, an energy adviser to the Pentagon, has estimated that it costs the U.S. $100 for every gallon, when the cost of maintaining supply lines and security is taken into account.

In December 2005, then-Secretary of Defense Donald Rumsfeld directed his department to “do all it can” to save energy. He set up a task force headed by his deputy, Gordon England, and former Defense and Energy Secretary James Schlesinger.

The Air Force took the lead, winning an Environmental Protection Agency “Green Power” award in 2006 as one of the top 25 purchasers of green power.

It has since won four more energy awards, and is now the leading purchaser and user of wind energy in the United States.

Nellis Air Force Base in Nevada is powered by the largest solar-power array in the Americas — saving the government an estimated $1 million a year.

Dyess, Minot, and Fairchild Air Force bases purchase 100 percent of their electricity from renewable sources of energy.

Airmen and their families have been using biomass fuel at Hill Air Force Base in Utah since 2004, thanks to a 1.3 megawatt landfill gas project. In other words, they are creating gas from the air base’s trash.

But saving money isn't the only reason for going green. Maj. Gen. Richard Zilmer noted that 70 percent of U.S. military vehicles traveling on roads in Iraq's volatile Anbar province were oil tankers providing fuel for the troops, easy targets for roadside bombs. He requested that the Pentagon send generators that could convert trash into fuel to generate electricity, so that fewer oil trucks would be on the road.

Defense Life Sciences, based in McLean, Va., was given a contract to come up with a solution. It teamed with a group of researchers at Purdue University and developed two 4-ton “tactical bio-refineries” that they are preparing to send to Iraq next month. Each can run for 20 hours on a ton of trash — enough electricity to power a small village.

Organic garbage is fed into a reactor, in which it is fermented into ethanol. Then plastic, cardboard and other paper items are burned to create propane or methane. These elements are then combusted in a modified diesel engine to power a 60 kilowatt generator.

The prototype costs $1 million and is now ready to be tested in a war zone.

Tune in to Fox report at 7pm EST for more on this story.

Jennifer Griffin currently serves as a national security correspondent for FOX News Channel . She joined FNC in October 1999 as a Jerusalem-based correspondent. You can follow her on Twitter at @JenGriffinFNC.