Biodiesel saw wider adoption in 2013 as use of ethanol blends slowed among biofuel users, according to a federal report released this week.

Soybean oil remains the leading feedstock in biodiesel in 2013, making up more than half of all biomass resources used to produce biodiesel, according to the U.S. Energy Information Administration.

Other biodiesel feedstocks fell into three categories including crop-based feedstocks, animal fat-based feedstocks, and recycled grease. The leading crop-based feedstock for biodiesel was corn oil followed by canola oil and palm oil. The leading animal fat-based feedstock was white grease and tallow followed by poultry fat. Recycled waste such as cooking oil (known as yellow grease) accounted for about 10 percent of biodiesel feedstocks.

Biodiesel consumption has seen incremental growth since the early 2000s and wider adoption since 2012, according to the EIA. When used to fuel vehicles, biofuels are mostly consumed as blended transportation fuels as either ethanol blended with gasoline or biodiesel blended with diesel fuel. Corn is the primary feedstock for ethanol.

Biodiesel production reached almost 1.1 billion gallons in 2012, which was up from the 25 million gallons produced in the early 2000s, according to the National Biodiesel Board.

The U.S. government's fleet spent $20.04 million on the B20 biodiesel blend of 20 percent biodiesel and 80 percent diesel fuel in 2012, according to the Federal Fleet Report. That was about $4.8 million less than the 2011 expenditure.

On average, about 60 percent of the energy in feedstocks can be converted to deliverable biofuels. Biodiesel can also be used as heating oil.