Exporting U.S. coal to South Korean power plants could cut greenhouse gas emissions by 21 percent compared to burning it at less efficient U.S. plants, according to researchers at Duke University . The strategy could also generate more than $25 billion in economic activity in the U.S. and cut emissions of sulfur dioxide, nitrogen oxide, and particulate matter, the researchers say. For those benefits to occur, however, U.S. plants would need to replace the exported coal with natural gas, and South Korea must use the imported coal to replace dirtier sources of coal. South Korea’s coal-fired power plants are newer and significantly more efficient than those in the U.S. — efficient enough to offset emissions associated with shipping the coal across the globe, the researchers say. However, they also caution that further studies are needed to assess the scenario’s full environmental impacts, including water use, land use, and the degradation of vital habitats.