Many have been surprised by the "greening branches" of the U.S. military.

In May a report on climate change (PDF) was issued by the powerful MAB (Military Advisory Board), an organization of high-ranking U.S. military officials which not only acknowledged climate change (a dramatic about-face from the Bush years) but also detailed the many ways in which climate change could impact national security.

An initiative was recently put in place to track the U.S. military's carbon bootprint, and last week 12 military bases signed a deal with Enviance, a leading provider of carbon footprint tracking. Now the Navy is going hybrid.  

This is good news. The U.S. Department of Defense is the largest consumer of fossil fuels in the world, purchasing approximately $13 billion worth each year (at $40 barrel that's 325 million barrels of oil). So even slight efficiency improvements pay off big time.

A $33 million investment will upgrade the Navy's fleet of DDG 51 destroyers with a hybrid-electric drive. At lower speeds, an electric engine will kick in, reserving the fuel supply for higher speeds and increasing the overall fuel efficiency of the ship.

According to EcoGeek, the Navy estimates a 16 percent reduction in total fuel consumption or 12,000 barrels per ship per year. Some are skeptical about the performance increasing that dramatically -- after all the electricity is primarily created by an oil-powered generator -- but it does indicate the Navy's desire to go green, conserving money and the climate.

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