Executive Order S-1-07, the Low Carbon Fuel Standard (LCFS) (January 18, 2007), calls for a reduction of at least 10 percent in the carbon intensity of California’s transportation fuels by 2020. It instructed the Secretary of the California Environmental Protection Agency to coordinate activities between the University of California, the California Energy Commission (CEC) and other state agencies to develop and propose a draft compliance schedule to meet the 2020 Target. This report is the first of two by the University of California in response. This first study assesses the low-carbon fuels options that might be used to meet the proposed standard, and presents a number of scenarios for mixes of fuels that might meet a 5, 10, and 15 percent standard. The second part of the study, to be released one month later, will examine key policy issues associated with the LCFS.