Biodiesel consumption reached a peak level in 2015 with nearly 2.1 billion gallons reducing carbon emissions by at least 18.2 million metric tons, according to the National Biodiesel Board.

Fuel companies produced 2.09 billion gallons of biodiesel during the year, an increase from the 1.97 billion gallons produced in 2014, according to the board, which cites data from the U.S. Environmental Protection Agency.

"We're seeing it take hold across the country," said Joe Jobe, chief executive for the board and the industry's trade association. "Consumers are seeking out cleaner alternatives to fossil fuels and they see biodiesel as a high-performing, cost-competitive alternative to petroleum diesel. These numbers also show without question that the Renewable Fuel Standard is delivering significant volumes of advanced biofuel to the American people. They prove that the RFS is absolutely working."

The board cited a "trouble trend" of "predatory imports" of biodiesel. Domestic biodiesel production remained flat at about 1.42 billion gallons, compared with about 1.47 billion gallons in 2014 and 1.50 billion gallons in 2013. Meanwhile, imports rose from 510 million gallons in 2014 to an estimated 670 million gallons in 2015, a jump of more than 25%.

The board has urged Congress to reform the $1-per-gallon biodiesel tax incentive from a blender’s credit to a producer’s credit. Under the existing blender’s structure, biodiesel produced overseas and blended in the U.S. is increasingly taking advantage of the incentive, sending U.S. tax benefits to foreign producers, according to the board.

Biodiesel is a renewable, clean-burning alternative fuel that replaces petroleum-based fuel in diesel engines. It's made from a mixture of resources such as recycled cooking oil, soybean oil and animal fats. It qualifies under the EPA's definition of an advanced biofuel, meaning that it reduces greenhouse gas emissions by more than 50% over petroleum diesel.

The data release comes on the eve of the 2016 Biodiesel Conference and Expo from Jan. 25 to 28 in Tampa, Fla.