National Geographic Article Natural Gas For Long Haul Trucking

Here's the article. Over the last year Clean Energy Fuels has built 70 fueling stations in 33 states.

Clean Energy Fuels is already the largest supplier of natural gas for transportation in the United States. But most natural gas vehicles on U.S. roads today are cars, buses, and small trucks burning a form of natural gas known as CNG-compressed natural gas. In the U.S., these vehicles typically run "point-to-point" or round-trip routes in city bus systems, municipal car fleets, and local delivery services.

But CNG tends to be unsuitable for long trips because it has a relatively low energy density, a measure of how much energy can be stored in a given tank size. In practice, this means impossibly large volumes of the stuff would be required to power a vehicle for more than 150-300 miles (240-480 kilometers) between fill-ups. By contrast, a diesel truck of average efficiency can cover 900 miles (1,450 kilometers) on the fuel held in a single 150-gallon (570-liter) tank.

Enter liquefied natural gas. Known as LNG, this super-chilled and compressed form of natural gas has about 60 percent of diesel's energy content by volume, and it is significantly more energy dense than CNG. As a result, heavy trucks equipped with thermos-like cryogenic tanks can haul freight long distances—often 400 miles or more—between LNG fill-ups.

LNG is currently selling for about $2.92 per diesel gallon equivalent. Diesel is about $4.16 per gallon. The price premium for LNG trucks is about $40,000 to $80,000, but that cost is recouped within three years without any government subsidies.

Although the burning of natural gas produces 30% less carbon dioxide than burning diesel, methane leakage during the production of natural gas reduces the advantage natural gas has to only about 6% to 11%.

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