Unfortunately, the two conventional methods for extracting hydrocarbon fuels from coal (indirect and direct liquefaction) are extremely expensive to implement, consume large amounts of water, and produce unacceptable amounts of atmospheric CO₂ and other pollutants. For this reason DARPA’s Strategic Technology Office is interested in exploring alternative coal to liquid fuel conversion technologies that offer environmentally friendly, yet efficient, methods for extracting useful energy from our Nation’s coal resources.

—DARPA-BAA-08-58

The US Department of Defense (DoD) currently uses on average more than 300,000 barrels (12.6 million gallons US, 47.7 million liters) of petroleum-based liquid fuels per day. Given the estimated US coal reserves of 275 billion tons, existing CTL technologies could meet the DoD need for liquid fuels “for several thousand years”, according to DARPA.

However, the agency notes, there are economic and environmental challenges that prevent the implementation of existing CTL technologies for producing JP-8 aviation fuel. The current cost of implementing a 100,000 bpd CTL facility would be well over $6 billion, according to DARPA. In addition, the life cycle environmental cost of fuels derived from coal results in a net increase of 80% or more in terms of carbon dioxide emissions as compared to the use of petroleum-based fuels.

While the use of proposed carbon capture technologies might mitigate the increased carbon dioxide emissions, the scalability, reliability, and economics of these technologies are still very much unknown. Finally, existing CTL technologies rely on large amounts of water as a source of hydrogen. This is due to the fact that coal, while high in carbon content, is comprised of only 5% hydrogen. In contrast, JP-8 has closer to 15 % hydrogen composition by weight. Water is a natural source for hydrogen (11% hydrogen by weight); however the water based reactions for converting coal to liquid fuels (water gas shift, steam reforming, etc.) result in the excess carbon and oxygen reacting to produce the additional unwanted carbon dioxide that is a major disadvantage of existing CTL technologies.

The development and demonstration of an innovative approach to CTL fuels that overcomes the economic and environmental challenges of existing approaches would be a revolutionary advance in the DoD’s ability to meet its requirements for a secure energy source.

—DARPA BAA-08-58

FT-based CTL (indirect liquefaction) produces about 1.3 kg of CO₂ and 0.27 kg of oil, while consuming 1 kg of water, for every kilogram of coal processed. DARPA believes that innovative CTL concepts may exist that result in zero carbon dioxide emissions by avoiding the production of carbon dioxide, and that water consumption per kg of coal could be reduced to less than 0.5 kg.

Basic metrics for the solicited projects are:

• Capital cost < $15,000 barrels per day (bpd) capacity

• End user cost < $3 per gallon for JP-8 aviation fuel

• Scalable to 100,000 bpd

• Zero carbon dioxide emissions (up to the 100,000 bpd production levels)

• < 235 kg of water consumed for every barrel of fuel produced (equivalent to < 0.5 kg of water for every 0.27 kg of fuel)

DARPA cautions that incremental improvements to existing Fischer-Tropsch or other existing CTL processes are not appropriate for consideration under this BAA.

The opportunity is limited to one Government fiscal year’s worth of funding. DARPA is anticipating multiple awards, but the combined maximum amount of all awards will not exceed $4.56 million.

Proposals for first selections are due 12 November 2008.

The Defense Advanced Research Projects Agency (DARPA) is the central research and development organization for the US Department of Defense (DoD). It manages and directs selected basic and applied research and development projects for DoD.

Resources

• DARPA Broad Agency Announcement: Coal To Liquids (CTL) (DARPA-BAA-08-58)