Think China’s coal-fired power plants are dirty? You haven’t seen anything yet.

The country plans to build up to 40 massive projects to convert coal to synthetic natural gas (SNG), a process that would dramatically increase China’s greenhouse emissions, and emit huge volumes of toxins while consuming vast quantities of water, according to a study released today by Duke University.

Given China’s recent pledge to cut coal consumption, what gives? In short, China has become a voracious consumer of natural gas—the largest in the Asia Pacific region—and is seeking to lessen its dependence on overseas suppliers of liquefied natural gas (LNG). And while the Chinese government wants to clean up urban air pollution that shrouds cities like Beijing in toxic smog, it doesn’t really care about greenhouse gas emissions. Most of the approved SNG projects will be built far from Chinese metropolises.

So far the government has approved nine SNG projects to produce 37.1 billion cubic meters (1.31 trillion cubic feet) of synthetic natural gas a year. According to Duke University researchers Robert Jackson and Chi­Jen Yang, SNG emits seven times the greenhouse gases of natural gas. If it is burned to generate electricity, the carbon spew is up to 82% greater than a coal-fired power plant. Tailpipe emissions from a SNG-powered vehicle are twice those of a conventional car.

Bottom line: Over the 40-year life of China’s nine approved SNG plants, their carbon-dioxide (CO2) emissions would hit 21 billion tonnes, compared to three billion tonnes from a “natural” natural gas plant. If China builds the 40 planned SNG plants, their emissions would skyrocket to 110 billion tonnes of greenhouse gases over 40 years. China’s total CO2 emissions in 2011 were 7.7 billion tonnes (pdf).

It gets worse. Most of the nine approved plants would be built in desert regions and consume more than 200 million tonnes of water a year. To produce a cubic meter of SNG requires 6 to 12 liters (1.6 to 3.2 gallons) of water compared to 0.1 liters to 0.2 liter of water for a cubic meter of natural gas. “The water consumption for SNG production could worsen water shortages in areas already under significant water stress,” states the report, published in the journal Nature Climate Change.

Despite the Chinese leadership’s new power policies, coal still remains king, Jackson told Quartz. “China has abundant coal resources, and local and provincial interests push the system to use the coal,” he said in an email. “In my view, developing shale gas in China would be much smarter than making natural gas from coal, but unconventional energy extraction in China is still developing.”

The Duke scientists suggest Chinese officials study the US’s failed experiment with SNG. In the 1980s, the US Department of Energy provided a $2 billion loan guarantee to build the Great Plains Synfuels Plant. The plant went online in 1983 and within two years its operator filed for bankruptcy. The US Department of Energy bought the project for $1 billion and subsequently sold it for $85 million.

“Using coal to make natural gas may be good for China’s energy security,” Jackson, a professor of environmental sciences, said in a statement, “but it’s an environmental disaster in the making.”