Clean tech startup Accelergy announced that its technology for turning coal into liquid fuel is ready for commercial application and that major energy companies in China, South Africa, and the U.S. plan to build plants using the startup’s products.

The energy companies, which have not yet been named but are purportedly some of the “biggest in the world,” have signed letters of intent to use Accelergy’s technology in “multibillion-dollar” plants to produce fuels at commercial scale, said Rocco Fiato, vice president for business development.

“You typically don’t get into this business by launching pilot scale projects,” he said. “You do it by launching world class projects.”

San Jose, California-based Accelergy was founded in 2004 to offer research services to energy companies. In 2006, the company retooled and hired several dozen employees from major energy companies such as ExxonMobile.

Now the startup has developed a proprietary technology for turning coal into a range of fuels, such as gasoline, diesel, and jet fuel. Backed with $37 million in venture financing, Accelergy says its technology produces lower unit costs and carbon emissions than its competitors.

Coal-to-liquid technology is not new, having been first developed by Nazi Germany and later improved by the South Africans under Apartheid. But as oil prices have risen and concerns over energy independence have intensified, energy companies have shown increased interest in the technology. Enthusiasm is especially high in those countries with large coal reserves, like Australia, China, South Africa, and the U.S.

Peter Hebert, managing partner of Lux Capital Management, which backs Accelergy, said that if all the coal in North America were converted into fuels using the startup’s technology, 1 trillion barrels of liquid fuels, or four times the proven oil reserves of Saudi Arabia, could be produced.

South Africa’s Sasol, now privatized but having got its start as a national company under Apartheid, produces almost 40 percent of the African country’s fuel needs by converting coal and natural gas into liquid fuel and chemicals. Energy giant Royal Dutch Shell has been working with Chinese companies since 2004 to apply its technology for producing liquid fuel from coal.

In August, Australian-American Energy, a subsidiary of energy giant Australian Energy, signed a deal with the American Indian tribe Crow Nation to build the first U.S. coal-to-liquids plant. The Many Stars plant, to be built in the state of Montana, is planned to initially produce 50,000 barrels a day of diesel and other fuels.

Other large-scale coal-to-liquids plants are proposed or underway in Ohio, West Virginia, and Wyoming, according to an article in The International Herald Tribune published in August.

The U.S. Department of Energy is funding research into what it calls “ultra clean” coal-to-liquids technology as part of its broader $62.4 million funding for clean coal research projects.

But interest in coal-to-liquids technology comes as the coal industry faces rising criticism over its role as a large source of greenhouse gasses. Some groups, such as the Natural Resources Defense Council, say that the total carbon emissions, including production and use, per gallon of petroleum-based fuels are about half that of total emissions from coal-derived fuels. The New York City advocacy group said that increased use of coal would mean more clear-cutting of forests and increased risk for groundwater contamination.

Mr. Hebert said Accelergy’s fuel was designed so that its carbon footprint is not greater than refined petroleum products.

“Accelergy’s technology yields energy-dense fuels from abundant resources—without adverse environmental impact,” he wrote in an email.

Accelergy initially intends to license its technology to companies building plants. But Mr. Fiato said the startup would not rule out participating in production in coming years.

“We have a deep bench of people from the energy industry,” he said. “We are building on that knowledge base.”

Accelergy is backed by Advent International, Goldman Sachs, Lux Capital, Mobius VC, Nth Power, Sequoia Capital, and Technology Partners.