When it comes to lower-emission alternatives to diesel in long-haul trucks, natural gas has some positives.
In addition to being cleaner burning, the fuel is in abundant supply, and doesn't come with any severe range or performance shortfalls.
But the extra cost of natural-gas powered vehicles has largely kept fleet operators away.
Even though natural gas is often cheaper than diesel, operators still may not be able to amortize the higher purchase price over the operating life of a truck.
However, policy changes surrounding liquefied natural gas (LNG) could boost the appeal of natural gas with truckers, according to Navigant Research.
Unlike compressed natural gas (CNG), LNG is cooled until it transitions from a gaseous to a liquid form.
LNG is denser than CNG, and hence easier to transport by road in specially-equipped tankers. Gaseous CNG is generally transported via pipeline.
Earlier this year, President Barack Obama signed a bill that changed the tax code to give LNG fuel (along with propane), a more equal basis for taxation compared to diesel.
Previously, LNG was taxed by volume instead of energy content.
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Since a gallon of LNG has around 42 percent less energy by volume than a gallon of diesel, that made its effective tax rate much higher--bringing the retail prices of the fuels closer together.
The actual cost of natural gas fuel has dropped 50 percent since 2008, according to Navigant.
The research firm also expects the number of U.S. LNG fueling stations to double by 2020, to more than 210.
Natural Gas-powered Kenworth truck (Image: Flickr user TruckPR)
Analysts believe sustained low prices will encourage more fleet operators to install their own fueling infrastructure, and buy or convert more trucks.
Continued use of hydraulic fracturing ("fracking") to access shale oil deposits will likely keep natural gas readily available.
And if LNG does not catch on in North America, several infrastructure projects will make exporting it easier.
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The Quebec government recently approved construction of an LNG plant in Becancour, and the Goldboro LNG terminal in Halifax, Nova Scotia, recently received approval to export the fuel.
The U.S. Department of Energy has also reversed a previous policy, allowing the export of LNG and potentially increasing interest in LNG production.
Several U.S. LNG export terminals are reportedly being reopened, and new ones may open as well.