Under the LCFS, fuel producers are encouraged to report a slightly higher CI than they calculate to account for uncertainty in biorefinery performance (because they are penalized if the actual fuel CI is determined to be higher than what they report to the program). Uncertainty was considered for all life cycle stages (except fuel combustion; detailed in SI Tables ) (1) to provide a more accurate estimate of the total fuel CI and (2) to illustrate the potential range of fuel CIs that are currently unaccounted for under program provisions. Latin hypercube sampling was used to generate samples for Monte Carlo simulation. Ten-thousand samples were generated for the analysis.