Determine the physical characteristics and properties of all the fuels and feedstocks
Evaluate the chemical compositions of the fuels, feedstocks, and their storage vapors as well as the products of combustion of fuel production equipment
Outline scenarios for the production and distribution of fuels
Determine the emissions of NOx, CO, CO2, CH4, and NMOG for the processes involved with each scenario
Develop per-gallon fuel-cycle emissions estimates
Estimate vehicle fuel economy
Compare fuel-cycle emissions on a per mile basis
In this study, fuel-cycle emissions are first determined per unit of fuel, which allows for better comparison with other studies and provides better insight into the origin of the emission estimates. Thereafter, the emissions are related to fuel economy to determine gram per mile emissions. This approach allows other values for fuel economy to be investigated more readily.
1.4 Report Scope
Table 1-1 summarizes the fuel/feedstock combinations that were considered in this study. As indicated in the table, several fuel/feedstock combinations are complicated by the fact that several products are made from the same feedstock and many fuels can be produced from several feedstocks. Different mixes of feedstocks are also used in fuel production. For example, a variety of crude oil sources make up the feedstock for California refineries, and this mixture will change in the future. Methanol is currently produced from natural gas, while production from biomass has been considered as an option for the future. Natural gas is produced from gas fields as well as a byproduct of oil production, and the gas can be used for many purposes, including the manufacture of synthetic liquid fuels or methanol. LPG is produced during oil refining and derived from natural gas liquids, a product of natural gas production. Electricity can be produced from a myriad of feedstocks, which range in CO2 impact from solar energy to coal.
The alternative fuels listed in Table 1-1 are used to a limited extent in California. Many vehicles have been converted to operate on LPG and manufacturers are beginning to offer purpose built vehicles. Several thousand flexible fuel methanol vehicles (FFV's) have been built as production vehicles for operation in California. FFVs are capable of operating on either M85, gasoline, or any mixture of these fuels. Prototype fuel cell cars and buses and over 300 transit buses have also been operated on M100. Electric vehicles will make up a significant portion of California's vehicle fleet as part of ARB's Low-Emission Vehicle program. Expanded use of electric vehicles (EVs) has also been considered as a means of reducing emissions to meeting federal Clean Air Act emission requirements. The feedstocks in Table 1-1 may not all be used in the short term. The significance of feedstock options and combinations of fuels and feedstocks that are