Section 3. COPRODUCTION

(a) In general . Fuel produced from biomass (as defined in § 45K(c)(3)) and petroleum feedstocks using a thermal depolymerization process is a renewable diesel mixture if such fuel—

(1) Has been registered by the EPA under section 211 of the Clean Air Act (42 U.S.C. 7545); and

(2) Meets the requirements of ASTM D975 or D396.

(b) Amount of renewable diesel in mix- ture . If fuel is treated as a renewable diesel mixture under section 3(a) of this notice, only the portion of the mixture attributable to biomass qualifies as renewable diesel used in the production of a renewable diesel mixture. A taxpayer claiming a credit or payment with respect to fuel treated as a renewable diesel mixture under section 3(a) of this notice must use generally accepted scientific practices to establish the portion of the fuel that is attributable to biomass.