Challenges in determining the renewable content of the final fuels after co-processing biogenic feedstocks in the fluid catalytic cracker (FCC) of a commercial oil refinery

•FCC co-processing has been commercialised using oleochemical feedstocks.•A new method based on step change mass balance has been developed to quantify the impact of adding biogenic feedstocks.•A C14 approach require an acceptable physical mass balance from the processing unit.•Combining the C14 and step change mass balance approach is recommended. The long-distance transport sector will be difficult to electrify and will likely require lower-carbon intensive, drop-in fuels if the sector is to effectively decarbonize. Policies such as the low carbon fuels standard (LCFS) have proven to be particularly effective in encouraging oil companies to produce lower carbon intensity (CI) fuels that the long-distance transport sector can use. One way to reduce the carbon intensity of the fuels is to co-process lower carbon intensive feedstock at various insertion points within a refinery (e.g. the hydrotreater or the fluid catalytic cracker (FCC)). However, to obtain “credits” from the appropriate regulator the carbon intensity of the final fuel and the renewable content must be determined. To date several processes, such as material balance and C14/C13-tracking, have been used to determine the renewable content of the final fuels, with each of these methods having their own strengths and weaknesses. As described here, challenges such as the lack of consistent terminology, through to variations in the “background noise” encountered in typical refinery operation, have complicated carbon intensity and renewable content determinations. However, when a co-processing approach is used in a routinely operating refinery, a multiple regression-based mass balance approach (based on observed yield) combined with C14 analysis is able to determine the renewable content of the final fuels.