There's rising interest in the role of renewable fuels to help reduce greenhouse gases. By capturing solar power, a plant that’s turned into fuel for a conventional engine has a measurable impact on a machine’s carbon footprint.

Renewable fuels include ethanol and biobased diesel — the latter comes in two types, biodiesel and renewable diesel.

Allen Schaeffer, executive director of the Diesel Technology Forum, says the "differences in biodiesel and renewable diesel have more to do with processing of the feedstock."

He explains that biodiesel fuel is derived from soybean oil, is chemically a fatty acid methyl ester and meets ASTM standard D6751. In making biodiesel, the process breaks the bond between fatty acids and glycerol, and replaces it with a methanol bond. Glycerin is a byproduct.

The fuel can be drop-in ready for a diesel engine at rates up to 20%; however, 100% biodiesel can be used in some instances. It cannot be moved by pipeline and can cause moisture to build up in fuel tanks. However, millions of miles have been racked up by trucks and tractors using the fuel with little problem.

Renewable diesel

Renewable diesel is also made from vegetable fats, often soybean oil, along with used restaurant grease and other products. Schaeffer says this is chemically known as a non-esterified renewable diesel, or NERD.

"Renewable diesel undergoes a more conventional petroleum industry, refinery-like processing that results effectively in a drop-in hydrocarbon," he says.

Renewable diesel meets ASTM standard D975, which means it is similar to petroleum-based diesel, can be moved over pipelines and can be a drop-in replacement for conventional diesel.

Paul Winters, public affairs director for the National Biodiesel Board, says as a paraffinic fuel, renewable diesel can be upgraded to jet fuel, meeting that ASTM standard.

Also, “both biodiesel and renewable diesel can substitute for heating oil," he adds.

Heating oil has become a more popular market for biobased diesel, as cities and states look at their greenhouse gas emissions.

Opportunities ahead

Winters says the United States in 2020 used 2 billion gallons of biodiesel and about 1 billion gallons of renewable diesel. "There have been several high-profile announcements about planned U.S. renewable diesel production recently," he adds. "U.S. renewable diesel capacity could grow by another billion gallons in the next few years and essentially catch up to biodiesel capacity, if all the announced plans come to fruition."

One example, announced recently, is an agreement between Shell Rock Soy Processing in Iowa and Phillips 66. Shell Rock will supply soybean oil for sustainable fuel production, including renewable diesel.

Winters says the National Biodiesel Board believes the U.S. market for both forms of biobased diesel will double to 6 billion gallons by 2030, providing growth opportunities for the entire industry. "That could include growth in demand for cleaner home heating oil, as well as transportation and sustainable aviation fuel. But the overall driver is for low-carbon fuels," he says.

The good news for farmers is that both forms of biobased diesel use similar feedstock that can help keep demand pressure up on soybean oil for the future.