Coal-powered synthetic natural gas plants currently being planned for construction in China would produce seven times more greenhouse gas emissions than conventional natural gas plants, according to a new study.

In the largest investment in coal-fueled synthetic natural gas plants in history, the Chinese government recently approved the construction of nine large-scale plants that, together, would produce more than 37 billion cubic meters of synthetic natural gas annually, according to the authors of the study.

Meanwhile, private companies are planning to build an additional 30 other plants that combined would produce as much as 200 million cubic meters of natural gas annually, or far more than China's current demand for natural gas.

Such energy security, however, comes at a steep price, the scientists warn.

"If all nine plants planned by the Chinese government were built, they would emit 21 billion tons of carbon dioxide over a typical 40-year lifetime, seven times the greenhouse gas that would be emitted by traditional natural gas plants," Robert Jackson, the director of the Duke Center on Global Change and lead author of the study, said in a statement. "If all 40 of the facilities are built, their carbon dioxide emissions would be an astonishing 110 billion tons."

According to the analysis, should the gas produced by the new plants be used to generate electricity, the total lifecycle greenhouse gas emissions would be 36 percent to 82 percent higher than pulverized coal-fired power; if used to fuel vehicles, the lifecycle greenhouse gas emissions would be twice that produced by gasoline-fueled vehicles.

"Using coal to make natural gas may be good for China's energy security, but it's an environmental disaster in the making," Jackson said.

Based on their findings, Chi-Jen Yang, co-author of the study and a research scientist at the Center on Global Change, stated: "At a minimum, Chinese policymakers should delay implementing their synthetic natural gas plan to avoid a potentially costly and environmentally damaging outcome."

Though, he said, "An even better decision would be to cancel the program entirely."