WASHINGTON -- The Navy plans to test-fly its main attack aircraft, the F/A-18 Super Hornet, on a biofuel blend this Earth Day, part of an ambitious push by the Pentagon to increase U.S. security by using less fossil fuel.

While deliberations grind on in Congress about how to shift the nation's energy away from fossil fuels, the Defense Department is putting plans into action with such things as electric-drive ships that save fuel costs, solar-based water purification in Afghanistan that reduces the need for dangerous convoys, and solar and geothermal power at U.S. bases.

The changes eventually could spread to civilian life. The size of the military's investment will create economies of scale that help bring down the costs of renewable energy, and military innovations in energy technologies could spread to civilian uses, just as the Internet did. In addition, military innovations could help reduce the nation's overall emissions of heat-trapping gases from fossil fuel use.

Navy Secretary Ray Mabus said the Defense Department looks at energy changes as "one of America's big strategic imperatives -- to reduce our reliance on foreign sources of fossil energy, to make us better war fighters and to get us more down the road to energy independence. We also feel the military can lead in this regard."

He said there also were added benefits -- "making us better stewards of the environment and helping our country move toward a different economy, which we cannot afford to fall behind in."

The Navy has changed energy sources before -- from sailing to coal in the 1850s, from coal to oil in the early 20th century and to nuclear power in the 1950s. Some people always warned against abandoning proven technologies for more costly ones, Mabus said. "Every single time they were wrong, and every single time it made our Navy and Marine Corps more efficient and better fighters. We're absolutely confident that will be the case again this time."

A report released Tuesday from a team of energy and security experts assembled by the Pew Charitable Trusts takes a broad look at what the military has done so far to move off fossil fuels. Some examples:

--The Army plans to have 4,000 electric vehicles in the next three years, one of the biggest electric fleets in the world.

--The Air Force plans to provide 25 percent of the energy at its bases with renewable energy by 2025 and use biofuels blends for half its aviation fuel by 2016.

--The Navy plans to launch a strike group by 2016 that runs entirely on non-fossil-fuel energy, including nuclear ships, combat ships that run on hybrid electric power systems using biofuels and aircraft that fly only on biofuels.

The Navy's first amphibious assault ship with a hybrid gas-electric drive was the USS Makin Island. On its first voyage last year from Pascagoula, Miss., around South America to San Diego, its home port, it saved nearly $2 million in fuel costs.

The Super Hornet is Navy aviation's largest energy user. It's being put through a series of tests, including the one planned Thursday at Naval Air Station Patuxent River in southern Maryland. The Navy is using an aviation biofuel made from the camelina sativa plant, a nonfood plant in the mustard family. The plant can be grown in rotation with crops such as wheat instead of letting fields lie fallow, so it provides farmers with another crop without taking land away from food production.