One would want to migrate towards fuels with the lowest carbon and other emissions. 

A second consideration is the amount of fossil fuel and carbon emissions associated with the producing and delivering fuels to customers.  Some fuels are subsidized by government incentives, which can further mask the total cost of (in dollar or environmental terms) of a particular fuel source.

Electricity can power vehicles – with the underlying carbon footprint dependent on the source of power used to generate that electricity.  So electricity from renewable sources would have a nearly zero carbon footprint (except for the green house gas emissions associated with the manufacture of the vehicle and of the electric generation equipment) while electricity generated from coal can have a proportionately high carbon footprint.  Similarly, fuels like ethanol and bio diesel have a different carbon footprint when made from corn, verses switchgrass, vs algae (from greatest to least carbon footprint).

Check out how this 1983 Mercedes was converted to run on vegetable oil by clicking on the image.

An accurate comparison of fuel alternatives would include the total carbon footprint embedded in the production as well as the use of that alternative fuel, also known as a "full fuel cycle assessment.” 

Coal gasification is a technology for turning coal into gasoline that can be used in cars.  Proponents of this technology focus on the prevalence of coal in KY and the benefit of involving an established state industry into alternative fuels.  Detractors of coal gasification note the high carbon footprint when coal gasification’s full fuel cycle is assessed.

Click here to read more about sorghum-based ethanol - an alternative fuel that could have an impact on Kentucky.