PERU, Ind. (AP) — The U.S. Department of Defense has an annual energy budget of approximately $20 billion, which accounts for nearly 80 percent of the federal government's total energy consumption, according to a recent study by The Pew Charitable Trust.

U.S. military bases alone rack up a $4 billion energy bill annually.

It's an astronomical chunk of change, but it's a number that has shrunk a little thanks to energy-saving initiatives launched at Grissom Air Reserve Base.

"The DOD is definitely looking at becoming more green," Tech. Sgt. Mark Orders-Woempner with the 434th ARW Public Affairs office told the Kokomo Tribune. "Every base has its own unique mission sets, and every facility has its own characteristics. But across the board, the DOD is looking for innovative ways to save money and protect the environment."

One of the most innovative and groundbreaking projects at Grissom was the recent installation of a $100,000 geothermal heating and cooling system. It's the first unit of its kind ever installed on an Air Force Reserve Command base.

Geothermal energy uses the earth's natural heat to help heat and cool buildings.

Engineers drilled 28 wells 300 feet into the earth to install a closed-loop, geo-exchange system that's now heating a nearly 15,000-square-foot facility at a fraction of the cost.

Geothermal systems wouldn't work on every base, but a study conducted by engineers revealed it would work at Grissom.

It was Sam Pier, 434th Civil Engineer Squadron mechanical engineer, who first looked into a geothermal unit. Grissom was renovating the facility, and Pier had some experience with geothermal exchanges. He said he wanted to incorporate the technology into the renovation design.

"When we knew the building was going to be renovated, Wayne Raby, 434th CES project manager, and I sat down and thought about what type of systems we wanted to utilize in the 14,900-square-foot facility," Pier said. "I had experience with residential-type geothermal units and wanted to see if there was a way to incorporate that technology here."

Now, Orders-Woempner said the system will pay for itself in around 10 years and start cutting back the base's energy bill immediately.

Other energy-saving upgrades include the installation of low-flow plumbing, better HVAC controls, energy efficient lighting, and infrared heating systems. Grissom spent more than $900,000 last year on those projects.

The base also dramatically reduced its fuel consumption last year after it purchased a $3 million virtual training system.

The new boom operator weapons system trainer, or BOWST, opened in September and allows KC-135 Stratotanker boom operators to undergo vital training necessary for in-flight refueling missions in a virtual environment.

A boom operator is part of a KC-135's three-person aircrew and uses a large boom to establish a connection between the tanker and the receiver aircraft to transfer fuel.

With boom operators stepping out of the airplane and into the simulator, the base is saving around $3 million a year on fuel costs by reducing the number of flight hours in a KC-135 Stratotanker while still offering the required training to get a boom operator certified.

"It's a money saver, because it costs about $300 per hour to run the BOWST, and it costs almost $7,000 an hour to fly the airplane," said Gary Beebe, a site manager with a contract company that operates and maintains Grissom's BOWST and KC-135 cockpit simulator. "It's almost a 20-to-1 ratio, and it has cut down on the number of flying sorties that it takes to get a boom operator initially qualified."

Just like the geothermal system, Grissom is the first Air Force Reserve Command base to have a BOWST.

On top of the cost-saving benefits, Grissom's virtual system also allows for enhanced training with emergency procedures and makes it easier for boom operators to train on all types of receivers.

"It allows us to train boom operators in abnormal and emergency processes that we can't safely recreate in the air," said Beebe. "You also don't have to fly to get to a different receiver. Just flip a switch and a fighter becomes a C-17."

Eventually the simulators will be able to link with other Air Force simulators around the world, allowing for receiver and tanker crews to perform complete aerial refueling operations in a virtual environment.

Besides energy-saving initiatives, Grissom also started maintaining nearly 3 acres of protected wetlands last year. Crews installed hiking paths through the area, and workers at the base now use it as a recreational site.

"We've got all sorts of gorgeous wildlife that live on base," Orders-Woempner said. "Our environmental specialist works hard to keep it the way nature intended it. The land is where we train. The environment is where we train. We don't want to train on an environment that's polluted and tainted."

The base's recycling program also continues to grow each year, he said. Last year, Grissom recycled 174 tons of material, including 91 tons of scrap metal, 48 tons of cardboard, 29 tons of paper and 2 tons of used tires.

The recycling program brings in more than $20,000 annually, which is used in future conservation efforts.

"Recycling has truly become a way of life around Grissom," Orders-Woempner said. "It's a culture. You can't walk 20 feet without running into a recycling bin somewhere."

The initiatives at Grissom are part of a larger push by the DOD to ensure access to reliable sources of energy. According to the Pew study, reliable, renewable energy is important for mission assurance, cost savings and compliance with laws and regulations.

But Orders-Woempner said maybe the biggest reason for the upgrades at Grissom is this: It's the right thing to do.

"It saves money, which is great, as the Air Force continues to look to cut back," he said. "But it's just the right thing to do. We want to be good stewards of the land that we've been given by the American taxpayer . If you're protecting the U.S. from all enemies, then environmental pollution is just as much a threat as anything else, in my opinion."