There is no reason why the United States cannot produce large quantities of synthetic fuels from coal and oil shale in the arid West if the plants are designed to recycle their water supplies, according to a Massachusetts Institute of Technology engineer.

"Every design I've seen of a synthetic fuels plant makes no allowance for reuse and recycle of the water needed to cool the plant down and flush away the mess the plants create," Dr. Ronald F. Probstein told the National Academy of Engineering last week. "By recycle and reuse, you cut water consumption to one-tenth what the designs say you need."

Synthetic fuel production has been a point of controversy in the West, where many people fear such production would take water needed for agriculture and commerce.

But Probstein said he believes the United States could produce from coal and shale the synthetic equivalent of 6 million barrels of oil a day, almost as much as the United States imports today from foreign oil producers.

"I'm talking about plants that would produce the equivalent of 1 million barrels a day in each of the five coal-bearing regions and in the single oil-shale region of the country," Probstein said. "Even in the most arid coal regions of the West, like New Mexico, these production figures are possible."

The MIT engineering expert said the designs he'd seen of synthetic fuel plants were extremely wasteful of water. Probstein said one popular plant design used an extraction technique that boiled away 1.5 million gallons of water every day and a flushing method that ended up with water being used for dust control on nearby roads.

"If you calculate the areas of dusty roads one of these plants would water in New Mexico," Probstein said, "you'd get the equivalent of 1,000 inches of rainfall a year."

Probstein insisted that even the most expensive technique of water recycle and reuse would increase the cost of the plant by lass than 10 percent. He said plants to extract synthetic liquids from coal could be built to recycle and reuse water at an added cost of 5 percent.

Calculations by Probstein showed that a plant producing 10,000 barrels of liquid synthetic fuel could do so using no more than 10 million gallons of water a day provided that the plant recycled its waste water and reused its clean water.

"You could go as low as 5 million gallons of water a day in some synthetic liquid plants," Probstein said. "Most estimates have synfuel plants that size using 100 million gallons of water."

Water is essential in the extraction of synthetic liquid and gas fuels from coal and shale, partly to cool down the furnaces and retorts needed to heat the coal and partly to flush away the wastes built up during the extraction process. More water is needed to extract gas from coal because water is used to make hydrogen during the gasification process.