The effect of used cooking oil composition on the specific CO₂e emissions embodied in HEFA‐SPK production

Abstract

In this study, the correlation between the composition, hydrogen/carbon (H/C) ratio, and hydrogen/oxygen (H/O) ratio of a used cooking oil (UCO) and the specific emissions embodied in the derived hydroprocessed esters and fatty acids synthetic paraffinic kerosene (HEFA‐SPK) is investigated. It is shown that HEFA‐SPK produced from UCOs with low concentrations of C18:1, high concentrations of C18:2, and low H/C ratios utilize less energy and more hydrogen during Fuel Production. Hence, HEFA‐SPK produced from such UCOs will embody higher gCO2e for fossil hydrogen utilization scenarios, and lower gCO2e for green hydrogen utilization scenarios compared with other UCOs. Conversely, it is shown that HEFA‐SPK produced from UCOs with high concentrations of C18:1, low concentrations of C18:2 and high H/C ratios utilize more energy and less hydrogen during Fuel Production. Hence, HEFA‐SPK derived from such UCOs will embody lower gCO2e for fossil hydrogen utilization scenarios, and higher gCO2e for green hydrogen utilization scenarios compared with other UCOs. Monte Carlo simulation gives the emissions embodied in Fuel Production a 95% confidence interval for all UCO‐derived HEFA‐SPK, showing a similar uncertainty for all compositions. A maximum of +1.1 gCO2e/MJSAF and −1.0 gCO2e/MJSAF is obtained for the upper and lower bounds respectively for the emissions embodied during HEFA‐SPK production from UCO. The application of the correlations founded in this study allows for the prediction of the specific emissions embodied in the feedstock‐to‐fuel conversion of any UCO, providing the C18:1 concentration, C18:2 concentration, H/C ratio and H/O ratio of the UCO is known.