Going green has become tactical necessity for U.S. military

The air around Bagram airfield, the main U.S. base in Afghanistan, is thick with the smell of jet fuel, the roar of aircraft taking off on bombing missions and the constant drone of electricity generators. Outside the ramparts, a snakelike convoy of brightly colored trucks waits to unload fuel hauled from Pakistan and Central Asia. These are the modern equivalents of the pack mules that once carried military supplies.

The British army calculates that it takes 7 gallons of fuel to deliver 1 gallon to Afghanistan.

Modern warfare would be impossible without vast quantities of fossil fuel. It is needed to power everything from tanks to jets to generators that run the communications networks on which Western armies depend.

In the punishing climates of Iraq and Afghanistan, moreover, soldiers' accommodations must be kept cool in hot weather, and warm in the cold. U.S. forces use more than 1 million gallons of fuel a day in Afghanistan, and a similar quantity in Iraq.

Until recently, military planners had assumed that fuel would be plentiful and easily available. A Humvee with armor gets just 4 miles per gallon; an Abrams tank uses 4 gallons per mile, in some conditions. These days, though, the United States' armed forces want to reform their gas-guzzling ways.

What has changed? During the invasion of Iraq in 2003, Marines often found themselves outrunning fuel supplies. Supply convoys became a favorite target of insurgents. In July 2006, Gen. Richard Zilmer, then in charge of U.S. forces in western Iraq, sent an urgent request for solar panels, wind turbines and other devices to reduce the need for liquid fuels. And in 2008, the spike in oil prices played havoc with military budgets.

'Military necessity'

In Iraq and Afghanistan, about 40 percent of fuel is used to run generators. A quick fix to reduce energy consumption was to coat military tents with commercial insulating foam, covered with a sealant to protect it from ultraviolet light. Joseph Sartiano, a Pentagon official, says this treatment halves the energy needed for air-conditioning. If the generators on a base are linked in a "smart grid" system, which optimizes operation and distributes power to priority areas, a further 20 percent savings is possible.

Another idea, already being tried at Camp Victory, the main U.S. base in Baghdad, is to convert rubbish into electricity. A machine called the Tactical Garbage to Energy Refinery (TGER), heats solid waste to produce synthetic gas -- a mixture of carbon monoxide and hydrogen -- ferments food slops to produce alcohol, and chemically processes the two to make biodiesel that powers generators. TGER produces as much as 64 kilowatts of power -- enough to run a battalion command post.

Such measures should reduce the amount of fuel needed to produce electricity. Much of the Pentagon's fuel goes to the Air Force, however, and reducing the consumption of jet fuel is much more difficult. The Air Force is working to certify all its aircraft to use synthetic fuels made from gas derived from coal or biomass. By 2016, the service seeks to use a 50-50 blend of synthetic and ordinary jet fuel for half of its aviation requirements within America.

But the shift toward synthetic fuel has provoked criticism, because when such fuel is made from coal and then burned in an aircraft engine, more greenhouse gases are emitted overall than would be produced if the aircraft simply burned conventional fuel derived from oil. Nor does it help reduce demand in war zones.

'Fully burdened' cost

For the foreseeable future, clean technology will flow mainly from the commercial to the military sector. But over time, new technologies, such as "blended wing" aircraft and new composite materials, may come out of military-funded laboratories. At the very least, the armed forces could act as crucial early adopters for costly new green technologies.