The estimated $45m agreement will come into force when Rock Mountain completes construction of its $5m refinery next summer in Fort Morgan, northeast of Denver.

The refinery will initially produce 4.5 million gallons a year of biodiesel, equivalent to 0.5% of annual petroleum diesel fuel consumption in Colorado.

“We are excited to be working with Gray Oil, a premier fuel distributor in the Rocky Mountain region, and market leader in the adoption and promotion of biofuels,” says Aaron Perry, chief executive of RMSE.

RMSE’s