The U.S. military has been talking about going green for years, and not just by consolidating the many colors of camouflage . In many respects, it’s the leader of the federal government’s renewable energy efforts.

In part, that’s of necessity. The Department of Defense is responsible for close to 80% of the federal government’s energy consumption. To move the needle towards Obama’s goal of having 20% of the federal government’s energy come from renewable sources by 2020, the DOD has to be onboard.

They are, and then some. The Navy is actually shooting for 50% clean energy by 2020, which is 2.5 times the goal for the government as a whole.

As Bloomberg reports, though, the effort isn’t all top-down politics. For the U.S. Army’s field operations, renewable energy is about safety.

There were 338 casualties in Iraq and Afghanistan in 2007, including one for every 24 fuel convoys, according to a report by the Army Environmental Policy Institute, the last one in which the military provided details on how soldiers were injured or killed. About half the materiel sent by convoy in 2008 was fuel and 20 percent was water.

To reduce casualties on the supply line, why not reduce the supply lines? Initiatives range from smarter to water recycling showers to easy-cooling tents.

With renewable energy, “there is no supply chain vulnerability, there are no commodity costs and there’s a lower chance of disruption,” Richard Kidd, the deputy assistant secretary of the Army in charge of energy security, said in an interview. “A fuel tanker can be shot at and blown up. The sun’s rays will still be there.”

The military still uses plenty of fossil fuels, of course. But their sheer size gives them power to move the market.

“At the installation level, the Department of Defense is the biggest energy buyer,” says Judy Marks, president and CEO of Siemens Government Technologies, which earlier this year developed the U.S. Army’s largest solar power system. “Larger than Walmart, larger than anyone else.”