cycle energy and global CO2 emissions. Twenty percent of natural gas feed is assumed to be associated with flared gas in Scenario 1. Flared gas is a large potential resource for fuel production. Many oil companies and some countries such as Nigeria have instituted policies to eliminate natural gas flaring. In Scenario 2, no credit for flared gas is attributed to FTD or methanol production with the assumption that the credit for flaring could be equally attributed to oil production.
Table 3-11: Natural Gas Transportation Assumptions for FTD and Methanol Production
Flared Gas Feedstock
Natural Gas Transport Distance (mi)
45% gas turbines
45% gas turbines
50% gas turbines
Many methanol plants are currently operating and under construction. With the apparent reduced use of MTBE, production capacity may exceed demand. Some methanol plants could be converted to produce FTD so the feedstock assumptions for the year 2010 are the same.
3.6.2 Synthetic Diesel Fuel Production
Synthetic fuels can be produced from the catalytic reaction of CO and hydrogen. The Fischer Tropsch (FT) process is one process that has been developed for fuel production. In recent years, developments in catalysts have allowed for the production of fuels in the diesel boiling point range. Synthetic diesel and Fischer Tropsch Diesel (FTD) are categorized together as all approaches for producing synthetic diesel are conceptually similar and result in the same emissions impact in California.
The FT process was originally developed in Germany in the 1920s to produce diesel from coal. FT plants are also operating in South Africa to make synthetic gasoline from coal. The FT process has three principal steps. First, a feedstock must be converted to synthesis gas, a mixture of carbon monoxide and hydrogen. Potential feedstocks include coal, biomass, and natural gas. A catalytic reactor converts the synthesis gas to hydrocarbons in the second step. The mixture of hydrocarbons consists of light hydrocarbons and heavier waxes. The majority of the hydrocarbons are saturated. In the third step, the mixture of hydrocarbons is converted to final products such as synthetic diesel fuel.
The FT process consists of three conversions:
Feedstock to a synthesis gas, a mixture of CO and hydrogen
Synthesis gas to hydrocarbons by use of a catalytic reactor