China is the world’s largest producer of coal and its largest consumer. The country relies on coal for 70 percent of its energy use. And China's appetite for energy is ravenous. The country is expected to build as many as 500 new coal-fired power plants over the next decade. But coal is the dirtiest of fossil fuels. It is responsible for the vast majority of greenhouse gas emissions in China. So the country is trying to modernize its coal-fired power plants to make them cleaner and more ...