How is Biodiesel Different than Renewable Diesel?

Renewable diesel is a hydrocarbon diesel fuel produced from renewable feedstocks. Today, all renewable diesel on the market is, like biodiesel, produced from fats and oils. The way these fats and oils are reacted into fuels is the defining difference between biodiesel and renewable diesel. As discussed above, biodiesel is primarily made through esterification. Renewable diesel is produced by hydroprocessing of fats and oils. Hydroprocessing produces alkanes, which are chemically identical to some of the compounds found in conventional diesel fuel. The properties of renewable diesel are also different from biodiesel. Like biodiesel, renewable diesel has near-zero aromatic content and very low sulfur content. It typically has a very high cetane number and a cloud point more like conventional diesel fuels. When used as a neat fuel (RD100), RD100 qualifies as an EPAct alternative fuel, while lower blends, such as RD20, do not.

The only way to determine if diesel fuel has been blended with renewable diesel fuel is through carbon dating using ASTM D6866. In this method, the isotopic ratio of fossil to biological carbon is quantified. Petroleum diesel will be wholly fossil carbon, while the renewable diesel (or biodiesel) content will be identified as biogenic carbon.