What is renewable diesel fuel (R99)?

Often called “green diesel” or “second generation diesel,” it refers to petrodiesel-like fuels derived from biological sources that are chemically not esters and thus distinct from biodiesel.

Renewable diesel (R99) is chemically the same as petrodiesel, but it is made of recently living biomass. The term ‘renewable diesel’ means fuel derived from biomass (as defined in section 45K(c)(3)) using a thermal depolymerization process that meets (A) the registration requirements for fuels and fuel additives established by the Environmental Protection Agency under section 211 of the Clean Air Act (42 U.S.C. 7545), and (B) the requirements of the American Society of Testing and Materials D975 or D396. The IRS’s ruling refers to any biomass process using heat as “thermal depolymerization” and the processed fuel is eligible for the $1-per-gallon blender’s tax credit.

Renewable diesel blends follow the same nomenclature as biodiesel. Renewable diesel in its pure form is designated R100 while a blend comprised of 20% renewable diesel and 80% petrodiesel is called R20. Because renewable diesel is chemically the same as petrodiesel, it can be mixed with petrodiesel in any proportion, but users may need to add an additive to address the lubricity issue associated with compounds with no oxygen.