A prototype coal liquefaction plant in Lexington has successfully converted slurry - consisting of coal and tar sands - into a quality crude oil substitute, University of Kentucky officials said.

The pilot plant, located at University of Kentucky's Center for Applied Energy Research, was the site of successful tests run earlier this year, proving the feasibility of a "co-processing" liquefaction technology, the university said.The work is part of a fossil fuel liquefaction science consortium consisting of University of Kentucky, the University of Utah, the University of Pittsburgh and Auburn University. The consortium is funded by the U.S. Energy Department and participating universities.

While conventional liquefaction involves the processing of coal slurry only, co-processing involves coal slurries with a heavy coal liquid substitute, such as petroleum residue or hydrocarbons recovered from tar sands.

Co-processing offers several advantages over conventional liquefaction, center spokesman Burt Davis said. The quality and quantity of the end product can be improved, waste is minimized and the plant is used more efficiently because the coal has to pass through the process only once, rather than three times.

Also, co-processing makes efficient use of low-value products, such as pertroleum residue from oil refineries or tar sands from locations such as western Kentucky.

"The quality of the end product is at least as good as most crude oil," Davis said.

The product could be refined in the usual way to make motor fuels, chemicals and other products. Like other synfuels, the product is more expensive than crude oil available on today's market.

"Synfuels are not as popular today as they were 10 years ago," said Davis. "But it's safe to say every petroleum company will say prices must go up. At some point it will be difficult enough to recover oil so that liquefaction will become economically attractive."