"Coal-Derived Fuel’s Advantages
Coal-derived liquid fuels are zero-sulfur paraffinic hydrocarbons that are similar to diesel. Because of its paraffinic nature, coal-derived diesel has a very high cetane number (about 75) compared to petroleum diesel (about 45). A high cetane number is necessary for efficient operation in diesel engines. The high paraffin content and low (less than 2% by volume) aromatic content also reduces particulate emissions. A test comparing coal-derived diesel with petroleum diesel on a 6.5-liter diesel engine for tactical vehicle applications showed that hydrocarbon emissions can be reduced by almost 50% compared to petroleum diesel. Carbon monoxide emissions were reduced by 50% and particulates by about 30%.
A potential approach to reducing CO2 emissions is to blend biomass with the coal feedstock. By doing so, the CO2 produced by the biomass fraction during production of the coal-derived fuel offsets the CO2 that was used up by the biomass during its growth phase by photosynthesis. Unfortunately, the logic cannot be extrapolated to a 100% biomass feed because of its low energy density and high moisture content (in comparison with coal) that leads to excessively high production and processing costs.
A recent study showed that by blending 15% to 30% biomass (by weight) with coal, the associated emissions can be 10% to 20% lower than the petroleum-derived fuel baseline.
In addition to environmental benefits, coal-derived liquid fuels have a high degree of thermal stability, which provides enhanced system performance for military aircraft. The DOD’s use of coal-derived liquid fuels could build public confidence and facilitate the introduction of such fuels into the private sector vehicle fleet."
We interrupt the excerpt so that we can emphasize the concluding paragraph:
"Overall, converting coal to liquid fuels is one element of an integrated approach that is needed to address fuel security. At least in the near term, it could bring a higher level of stability to world oil prices and to the global economy. Over the long term, it could serve as insurance for the U.S. (or any other oil-importing nation) against artificial or unwarranted price hikes from oil-producing countries."
It's difficult to state the benefits of coal conversion much better than that, except to offer the reminder that coal-to-liquid conversion technologies can be adapted to accept additional, renewable and CO2-recycling, biologically-based feed stocks, and be integrated with Sabatier-type processors for the direct capture and conversion of CO2 into even more hydrocarbon fuels and chemical manufacturing raw materials.