A different kind of truck stop is coming soon to Atlanta. Greg Roche, vice president for infrastructure at Clean Energy Fuels, is presently scouting locations to build one of the California-based company's natural gas fueling stations for long-haul trucks by the end of this year. With fracking techniques freeing more and more natural gas in the U.S., the alternative fuel is suddenly much cheaper than those made from petroleum.

"A trucker can save one third of his energy spend by switching to natural gas," Roche notes, thanks to the historically low prices for the gaseous fuel occasioned by the boom in U.S. shale gas development via hydraulic fracturing. "It's also good for the environment because it's the cleanest fuel available for big-rig trucks."

Clean Energy Fuels already operates six fueling stations dispensing liquefied natural gas (LNG) to the big trucks that ply the nation's highways, ranging from San Diego to Seville, Ohio. Truck stops that pump LNG can be distinguished by their tall, thin storage silos—capable of keeping up to 68,000 liters of this fuel at low temperatures and high pressures. The LNG, trucked in from big liquefying plants much like diesel fuel is trucked in from refineries, then powers the trucks over hundreds of kilometers. Such a station in the port of Long Beach, Calif., already can handle 1,200 trucks a day. 

"Trucks that you're making here at this plant run on natural gas, and that makes them quieter, it makes them better for the environment, it makes them cheaper to fill up," President Barack Obama said during a March 7 speech to announce his administration's expanded alternative vehicle efforts at a Daimler truck factory in North Carolina. "But, at the end of the day, it doesn't matter how much natural gas or flex-fuel or electric vehicles you have if there's no place to charge them up or fill them up."

That's the problem Clean Energy Fuels hopes to solve with "America's Natural Gas Highway," a bid to build more than 150 fuel stations from "coast to coast and border to border," as Roche says, at a cost of $1.2 million or more per station. "The competition is for people to keep doing what they've always done and keep using expensive foreign oil."

Locally compressed
Big rigs running on diesel fuel can cover roughly 1,900 kilometers between pit stops. Liquefied natural gas is the only other fuel that can begin to approach that kind of range, enabling truckers to cover more than 1,200 kilometers before refueling. Depending on the cost of diesel, switching to natural gas can save as much as $2 per gallon of fuel. That means the additional roughly $30,000 cost of natural gas trucks can be paid back in two years or less (assuming the trucks cover more than 95,000 kilometers a year).

At present, although the Daimler truck factory has built more than 1,000 natural gas-fueled trucks, engine options from the major truck manufacturers are limited. "Building a natural gas engine isn't that difficult," argues physicist Nicholas Cizek, a fellow at the Advanced Research Projects Agency–Energy (ARPA–E) who has worked on its Methane Opportunities for Vehicular Energy, or MOVE, project.

In fact, natural gas vehicles of all types are already popular in countries such as Argentina, India and Italy, among others. All told there are more than 13 million natural gas vehicles on the road worldwide. Gasoline taxes typically are used by national governments to promote the use of the alternative fuel. The idea is that natural gas, because it burns more cleanly than other liquid fuels and emits less carbon dioxide, reduces overall greenhouse gas emissions and other air pollution. In fact, Argonne National Laboratory estimates that natural gas vehicles emit 40 percent less CO2 than those that burn gasoline (pdf). But methane, the primary molecule in natural gas, is itself a potent greenhouse gas, and some studies have found that if significant amounts of unburned methane leak, whether during drilling, piping or fueling of natural gas, its emissions benefits may trickle down to none.

In the U.S. natural gas use has largely been confined to large institutional fleets, whether buses or garbage trucks, that return to local depots at night to refuel. The fleet vehicles are commonly fueled with compressed natural gas (CNG), which comprises the same methane molecules, albeit stored at lower pressures, which result in less dense fuel. Burning the compressed gas helps reduce pollution from these vehicles, and Clean Energy Fuels already operates nearly 300 stations dispensing CNG nationwide.

But compressed natural gas won't work for big rigs. "It's a simple physical problem," explains chemical engineer Patrick Davis, program manager for vehicle technologies at the U.S. Department of Energy, which also encompasses ARPA–E. "You can't package enough CNG on board a truck. It has to be LNG for no other reason than the density of the fuel. It's required for long haul."

Made in the U.S.A.
In a bid to wean the U.S. from the roughly $1 billion a day spent on importing oil, the Energy Department is funding a variety of efforts to develop natural gas–based alternative fuels. Miami-based start-up Vehicle Production Group also received an Energy loan guarantee for production of its minivan that runs on compressed natural gas burned in an engine built by Ford. For its part, MOVE is currently gathering applicants for $30 million in funding to explore better ways to store natural gas at both high and low pressures as well as opportunities to create affordable home refueling technology that might enable natural gas to become a fuel for the cars and trucks driven every day by Americans. The idea is to either find materials that can soak up methane like a sponge and store it at low pressures or to build a better (and cheaper) high-pressure storage tank.

Of course, one of the main reasons that natural gas itself remains cheap is that there are currently limited options for using it in the U.S. Either it must be burned in a power plant to create electricity or used in the chemical and fertilizer sector. Already, the federal government has approved plans to export liquefied natural gas as well as to begin to use it in vehicles—both of which would ultimately drive up its price, thereby making it less economically attractive as an energy alternative.

But if the U.S. were able to develop technologies to better use natural gas in vehicles, the nation could both reduce its trade deficit and potentially find a competitive advantage for the future. "If we can evolve robust technologies here and develop them for our domestic market, we can then export them to other places," Cizek argues.

And liquefying natural gas is only one of the ways to turn the gaseous molecule into a liquid fuel. "If we can convert it into a drop-in liquid fuel, that would be a great solution also," Cizek notes of alternative fuels that would not need pressurization and could directly substitute for petroleum-derived gasoline, diesel or jet fuel. "That's something we're investigating."

That would be a solution for the nation's largest single user of petroleum: the U.S. Department of Defense. "Natural gas won't work for us," Secretary of the Navy Ray Mabus said March 20 at the Bloomberg New Energy Finance Summit, because it would require retrofitting the armed forces' many engines. "We need drop-in fuels."

It will also take time for such an energy transition—from diesel to liquefied natural gas—to occur, requiring the build-out of refueling infrastructure, new vehicles and new plants to convert natural gas to liquid fuel. "I'm not aware of a current LNG engine product that completely gives you the performance of a diesel engine product, allowing a loaded class 8 truck to go over the Rocky Mountains in the same way a diesel would," DoE's Davis notes. "It is something that is going to take quite a bit of time, but we believe investments in LNG technology could yield substantial benefits in terms of using domestic energy sources and reducing our dependence on foreign oil."

Already, engine manufacturers such as Navistar have promised a full range of natural gas–burning engines, up to 450 horsepower, by mid-2013. And large-truck fleet owners are beginning to make the switch, ranging from Waste Management, which now buys almost exclusively natural gas–powered trucks, to parcel delivery companies. In part of its bid to reduce the company's use of six million liters of petroleum annually, FedEx plans to have its first prototype long-haul trucks burning LNG on the road this summer.

When it comes to the personal vehicle market, any natural gas cars would have to compete with electric cars such as the Chevy Volt, but the two alternative fuel options may be more similar than different. "An EV is a kind of natural gas vehicle," noted Edwin Feo, a managing partner at USRG Renewable Finance, at the Bloomberg summit on March 21. "It's just turned to electricity first."

In the meantime Clean Energy plans to invest with partners some $450 million in building its network of 150 natural gas refueling stations, including two in Atlanta. Georgia will also host natural gas refueling stations in Dalton and Tifton. "We will be at truck stops on the Interstate," Roche says, noting that the company also owns two plants in California and Texas that can create around 1.3 million liters of LNG per day. "The goal is to give [truckers] the same experience as when they get diesel fuel."