Global Environmental Benefits

Environmental performance associated with production and use of fuels is increasingly important as emission standards tighten in the United States and worldwide. Notably, the reduction of CO2 emissions in response to global climate change is one of the major challenges facing industrial, transportation, and other significant energy-using sectors.

Although there are a number of different demonstrated process routes for production of liquid fuels (chiefly gasoline, diesel fuel, and jet fuel) from coal, not all of which involve coal gasification, many of the most important methods are based on production of synthesis gas (syngas) from gasification of coal, which is converted to liquid hydrocarbons or alcohol for use as fuel or fuel refining feedstocks. Since impurities such as sulfur and mercury are removed from the syngas prior to fuels synthesis, the result is ultra-clean liquid fuels that burn with lower emissions than conventional fuels. Even in the case of non-syngas-based methods (i.e. direct coal liquefaction), technology has been developed that produces fuels meeting current fuel specifications, and the results often rival conventional (petroleum-based) fuels in contaminant profiles.

The National Energy Technology Laboratory (NETL) has a history of research and development in the area of liquid transportation fuel production from coal. Many of the technologies developed for conversion of coal to transportation fuels can also be leveraged for the conversion of biomass-derived feedstocks, either independently or in conjunction with coal, which has particular advantages in reduction of life-cycle CO2emissions. This work continues in several projects found in the collection of current projects being performed under the Coal & Coal-Biomass to Liquids program.

A significant example of NETL’s work in this area is the following study from 2011:

"Production of Zero Sulfur Diesel Fuel from Domestic Coal: Configurational Options to Reduce Environmental Impact"

This study evaluated the economic viability and environmental impact of producing diesel fuel via Fischer-Tropsch (FT) synthesis using syngas from coal or coal supplemented with biomass in the form of switchgrass (which can be grown on marginal land unsuitable for food crops). The commercial-scale plant assumed in this evaluation would produce 50,000 barrels per day fuels (700 million gallons per year) using commercially available technologies. Study results indicate that diesel fuel can be produced from coal that has a lower life-cycle greenhouse gas (GHG) emissions profile than conventional petroleum-derived diesel fuel on a well-to-wheels basis, assuming that CO2 produced at the facility is sequestered, and possibly requiring methane mitigation practices in the case of certain bituminous coals which are particularly high in methane content. If sufficient biomass resources are available to co-convert with the coal, the GHG emissions profile of the diesel fuel can be significantly reduced at a minimal increase in cost. For example, replacing 15 percent of the coal feedstock with switchgrass will result in diesel fuel which produces up to 34% less life-cycle GHG emissions than petroleum-derived diesel.

Study results show that Fischer-Tropsch synthesis is a near-term technology pathway which could be leveraged to produce large volumes of transportation fuels from domestic coal and biomass at reasonable cost and with sustainability in relation to emissions including greenhouse gases. This pathway enables improvement of the United States’ energy security, and at the same time addresses climate change concerns.