Renewable Diesel

Renewable diesel is a hydrocarbon produced most often by hydrotreating, processed to be chemically the same as petroleum diesel. It meets the ASTM D975 specification for petroleum diesel in the United States, can be used in existing infrastructure and diesel engines, and can be run as a full replacement or blended with petroleum diesel in any amount.

It is a different product from biodiesel and the distinction is the entire point. Biodiesel is a mono-alkyl ester made by transesterification, which is why it carries blend limits and its own cold-weather and storage handling. Renewable diesel has neither, because as far as the engine and the tank are concerned it is diesel.

That makes it the least disruptive emissions step available to a diesel fleet, which is an unusual thing to be able to say. There is no equipment to buy, no specification to rewrite, no operator training and no vehicle to take out of service. The constraints are supply and price rather than compatibility, and availability is strongly regional, so the practical question for most agencies is whether a supplier can actually deliver it to their tank at a defensible cost.

It is worth naming precisely in a specification or a fuel contract, because a document that says only “renewable” or “biodiesel” can be met with a product that behaves quite differently in a yard tank.