Plum will supply LNG to the mine haul vehicles, producing cost efficiencies and saving fuel.

Alpha Coal West began testing LNG technologies developed by GFS Corp in trucks at the Belle Ayr mine in 2012, starting a pilot program of the world's first LNG-powered mine haul trucks.

After 18 months of daily operation, Alpha Coal West decided to proceed with the conversion to LNG of its 16 Caterpillar 793 haul trucks at the nearby Eagle Butte mine.

The company expects the alterations to the trucks, each of which is capable of hauling 240 short tons of coal, or the equivalent of two railroad cars, to be completed by the end of 2014.

Plum's LNG plant at the Eagle Butte mine is due to come online in March next year and will be able to produce 28,500 gallons (107,884 litres) of LNG a day.

Plum has also designed an LNG refuelling station that will be constructed onsite at Eagle Butte, which will be capable of refuelling eight trucks simultaneously.

Plum CEO Kirt Montague said the project would also help solidify supply lines for other LNG users in the Powder River Basin.

Alpha Natural Resources president Paul Vining added that the construction of the LNG plant fitted with ongoing efforts to control costs.

“Switching the Alpha Coal West fleet to the combined use of LNG and diesel will also lead to more efficient operation and longer engine life for the trucks," Vining said.

Alpha Coal West's demand for LNG is expected to be about 6400 gallons a day to fuel its trucks.

As the plant grows, excess product can be sold to other companies in the area as they convert their haul trucks and other equipment to the lower emission and cost-efficient LNG.

Alpha Natural Resources is one of the largest and most regionally diversified coal suppliers in the US, with affiliate mining operations in Virginia, West Virginia, Kentucky, Pennsylvania and Wyoming.

It supplies metallurgical coal to the steel industry and thermal coal to generate power to customers on five continents.