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."
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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."