Can you guess what single organization consumes the largest amount of fuel in the world — more than any airline, more than any shipping firm and more than dozens of small nations? I am talking about the U.S. Department of Defense (DoD), which has really felt the pain of $100 oil as it conducts missions around the globe.

A convoy or army vehicles traversing Afghanistan is just one example. A whole raft of extra fuel-guzzling vehicles must line up at the front and the end of these moving supply chains just to provide extra security. Or think about a fighter pilot going up in the air to log his weekly practice hours. Each time, he’s burning dozens of gallons of pricey jet fuel.

The various U.S. missions really add up. Consider that the DoD burns 135 million barrels (4.2 billion gallons) of oil every year. To keep the lights on and run the computers, the DoD also must spend scarce dollars to generate 30 million MegaWatt hours of electricity each year. The total annual energy tab: $20 billion.

Thankfully, Washington has woken up to the problem. During the past decade, a series of programs have been launched to help find ways to sharply cut the DoD’s fuel bill. A handful of companies stand to benefit, and there is a clear opportunity for investors to profit.

Key goals of these programs include:

•  Sharply boosting energy efficiency at the DoD’s 300,000 buildings by installing lower-power lighting, and better Heating, Ventilation and A/C (HVAC) systems.

• Identifying and implementing clean energy sources at both fixed and mobile locations.

• Advanced building automation that controls light and temperature more precisely.

• Implementing micro-grids, which are self-contained islands of power generation and transmission. This is especially important for mobile camps where soldiers are far from the nearest base and any power grid.

• Supporting research to find ways to make jet fuel from biofuels, that at scale, promise to be cheaper that crude oil-based jet fuel.

You haven’t been hearing a lot about these efforts in recent years because the DoD has mostly been laying the groundwork to make these major changes. But in the next few years, as the DoD’s budget sharply shrinks, look for energy savings programs to scale up quickly.

Here’s a broad (buy by no means comprehensive) look at the types of efforts underway, and the companies that stand to benefit.

Solazyme (Nasdaq: SZYM)
There has been a raft of companies looking to create fuels out of abundant organic materials (instead of crude oil). Solazyme’s approach is getting the attention of the U.S. military because it’s algae-based approach can be modified to produce gasoline, diesel and jet fuel, all of which are used on base and in battle.

As an example, the U.S. Navy has been testing the company’s “Soladiesel.” The Navy and other branches of the military are coordinating their efforts to help test and develop the biofuels industry under its “green strike” initiative. Perhaps of greatest importance, Solazyme has partnered with a range of firms, including Tyson Foods (NYSE: TSN), Chevron (NYSE: CVX), Bunge (NYSE: BG), Unilever (NYSE: UN) and others. These partners are expected to cultivate a range of end-market opportunities for Solazyme that complement the current pursuit of military contracts.

Oshkosh (NYSE: OSK)
Shrinking defense budgets have pushed this stock down from $60 in 2007 and $40 in 2010 to a recent $23. The army is looking to shrink the number of rugged trucks in its fleet, which pushed Oshkosh’s sales down 23% in fiscal (September) 2011 to around $7.6 billion. Analysts don’t expect sales to rebound in fiscal 2012 or 2013, either.

Yet Oshkosh is working to break out of the rut by developing vehicles that carry fully-developed power systems onboard, enabling troops to plug into it when deployed in the field. “Most military trucks these days, including the ubiquitous Humvees — function as makeshift command centers, weapon launchers, ambulances, electronic jammers, and perform other roles, all of which require loads of electricity to run a smorgasbord of hardware,” notes a blogger for National Defense Magazine.

Oshkosh has already upgraded many of its vehicles to handle 400-amp alternators, and current research is aimed at delivering 1,000 amp units. Oshkosh focuses on medium-sized trucks (known as 7-ton trucks) and not the Jeeps and Humvees that most people recognize. Meanwhile, shares have been oversold on the impact of near-term defense spending cuts, according to Merrill Lynch. The firm suggests shares will rebound back to $30 as investors start look out beyond 2012.

Ultralife Batteries (Nasdaq: ULBI)
This provider of mobile communications and power systems for soldiers in the field struggled in recent years in the face of erratic sales and profits. The arrival of GE (NYSE: GE) veteran Michael Popielec at the end of 2010, however, should help stabilize results and, eventually, garner rising sales. His cost-cutting efforts have already taken root, and it appears to boosting results. Gross margins rose nearly three percentage points in 2011, to 30%. That gain came despite a pullback in sales that would normally impede margins from reduced manufacturing efficiencies.

A delay in battery orders was a key setback, though the military has resumed its purchasing, and Ultralife expects sales to rise by double-digits in 2012. Based on management guidance, this should help operating profits rise 50% this year. To back up the bullish outlook, Popielec recently bought roughly 40,000 shares at an average price of around $4.80.

Risks to Consider: If Washington gets gridlocked again in the next year, then defense spending may take even deeper hits than are currently anticipated. That would hamper the military’s ability to support these energy efficiency programs.

Action to Take –> These companies are pursuing projects that could be worth hundreds of millions of dollars in annual contracts. As these contracts take shape, investors are likely to seek the most investable angles in these key programs. You should keep tabs on these programs yourself and be ready to invest in your favorite angles whenever you think the time is right.

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