The scarcity of fossil fuel resources is causing considerable worldwide unrest, and current practices of energy production are unsustainable. The ability to make liquid fuels from domestic resources is therefore highly desirable, particularly given that the U.S. has abundant coal and natural gas.
Although methods to convert coal and gas to liquid fuels exist, standard processes are expensive and environmentally damaging. Current methods involve adding hydrogen (extracted from large quantities of water) to a costly, large-scale gasifier system. The synthesis gas is then catalytically converted to liquid fuels, but this process not only generates wax that must be recycled, it also emits carbon dioxide, a greenhouse gas.
With funding from the Defense Advanced Research Projects Agency, SRI developed a novel technique that enables the green and economical conversion of coal to liquid fuels. The process uses natural gas as the source of hydrogen that drives the reaction. By co-gasifying coal in this manner, SRI researchers have demonstrated the proof of principle for a process that is ideal for methanol production.
The technique, coupled with a commercial methanol-to-diesel conversion process, facilitates the transfer of all of the carbon in coal and methane to the desired liquid base. A process intensification step allows the use of a relatively small gasifier, which reduces initial equipment expenditures. The result is a cost-effective liquid fuel production method that uses no water and eliminates coal-associated carbon dioxide emission.