For the Defense Department, the largest consumer of energy in the United States, addiction to fuel has greater costs than the roughly $18 billion the agency spent on it last year.

    By some estimates, about half of the U.S. military casualties in Iraq and Afghanistan are related to attacks with improvised explosive devices on convoys, many of which are carrying fuel. As of March 20, 3,426 service members had been killed by hostile fire in Iraq, 1,823 of them victims of IEDs.

    "Every time you bring a gallon of fuel forward, you have to send a convoy," said Alan R. Shaffer, director of defense research and engineering at the Pentagon. "That puts people's lives at risk."

    Spurred by this grim reality, the Pentagon, which traditionally has not made saving energy much of a priority, has launched initiatives to find alternative fuel sources. The goals include saving money, preserving dwindling natural resources and lessening U.S. dependence on foreign sources.

    "The honest-to-God truth, the most compelling reason to do it is it saves lives," said Brig. Gen. Steven Anderson, director of operations and logistics for the Army. "It takes drivers off the road."

    Other than fueling jet engines, the largest drain on U.S. military fuel supplies comes from running generators at forward operating bases. The Pentagon says that the wars in Afghanistan and Iraq have required more fuel on a daily basis than any other war in history. Since the conflicts in Afghanistan and Iraq began in 2001 and 2003, respectively, the amount of oil consumption at forward bases has increased from 50 million gallons to 500 million gallons a year.

    To help reduce consumption, the Pentagon is using $300 million of the $7.4 billion it received from the economic stimulus package to accelerate existing programs for developing alternative fuels and saving energy.

    "In the overall scheme of the stimulus, it sounds small," Shaffer said. But he added that the relatively modest sum is being strategically targeted to make the most of it. "For $300 million, we have a lot of things that could be found."

    Garbage, for example, is a commodity never in short supply when the Army goes to the field. A battalion-size forward operating base generates a ton of trash a day. The Pentagon is developing mobile units - small enough to fit on a five-ton flatbed trailer - that use an anaerobic microbial process to convert garbage into oil.

    Two prototypes - known as the Tactical Garbage to Energy Refinery - were deployed to Iraq in the summer and were initially successful, converting field waste - paper, plastic, cardboard and food slop - into biofuel to power a 60-kilowatt generator. "We were able to get oil out of trash," Shaffer said.

    But the units were not particularly hardy and soon broke down. The stimulus money includes $7.5 million to develop a more rugged model.

    The Pentagon is also investing $15 million of the stimulus money into developing lightweight, flexible photovoltaic mats that could be rolled up like a rug and used at forward bases to draw solar power for operating equipment.

    "We think $15 million will let us build, develop and test one of these roll-out mats," Shaffer said.

    About $6 million is aimed at improving a program run by the Defense Advanced Research Projects Agency to convert algae into jet propulsion fuel 8, or JP-8, that could power Navy and Air Force aircraft.

    Other initiatives include $27 million to develop a hybrid engine the Army could use in tactical vehicles and $2 million to develop highly efficient portable fuel cells that could reduce the battery load carried by infantry soldiers.

    The Pentagon is also testing the use of solar and geothermal energy to provide power at installations. The Army, for example, is partnering with a private firm to build an enormous, 500-megawatt solar farm at Fort Irwin, Calif. The farm would supply the 30 to 35 megawatts needed to operate the installation, with the remaining available for sale to the California electrical grid.

    Fort Irwin's desert location is particularly well suited for solar energy, but the concept of using buffer land for energy production could be applied at many installations, said Keith Eastin, assistant secretary of the Army for installations and environment.

    "This buffer land could be used for solar farms, wind farms, whatever," Eastin said. "This would require almost no investment by the Army. This is a new way of thinking in the Army, to take advantage of the assets we have."

    For all the emphasis on new technologies at the Pentagon, one of the most successful initiatives involves decades-old technology: insulating thousands of tents in Iraq and Afghanistan with a two-inch layer of foam. The foam is sprayed like shaving cream from 55-gallon drums and hardens in about 20 minutes.

    A $95 million program to spray-foam tents in Iraq has dramatically reduced the amount of fuel needed for heating and cooling, saving $2 million in energy costs per day, Anderson said. It is also reducing the Army's logistical footprint, which includes roughly 900 trucks per day moving in and out of Iraq, he said.

    "We've already taken 12 trucks off a day," said Anderson, who previously served as deputy chief of staff for resources and sustainment for the multinational force in Iraq. "That may not seem like a lot, but it adds up pretty ... quickly. Those are some of the most dangerous roads in the world. I'm confident it has saved lives."

    A $29 million contract has been signed to insulate tents in Afghanistan, where vulnerable land supply routes pose serious challenges as the United States attempts to build up its forces.

    "If we're going to be in Afghanistan for a while, it behooves us to foam as many structures as we can," Anderson said.