This report is the first of two by the University of California in response to Executive Order S-1-07, the Low Carbon Fuel Standard (LCFS) (January 18, 2007), which calls for a reduction of at least 10 percent in the carbon intensity of California’s transportation fuels by 2020. 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.