Even as developed countries close or limit the construction of coal-fired power plants out of concern over pollution and climate-warming emissions, coal has found a rapidly expanding market elsewhere: Asia, particularly China.

At ports in Canada, Australia, Indonesia, Colombia and South Africa, ships are lining up to load coal for furnaces in China, which has evolved virtually overnight from a coal exporter to one of the world’s leading purchasers.

The United States now ships coal to China via Canada, but coal companies are scouting for new loading ports in Washington State. New mines are being planned for the Rockies and the Pacific Northwest. Indeed, some of the world’s more environmentally progressive regions are nascent epicenters of the new coal export trade, creating political tensions between business and environmental goals.

Traditionally, coal is burned near where it is mined — particularly so-called thermal or steaming coal, used for heat and electricity. But in the last few years, long-distance international coal exports have been surging because of China’s galloping economy, which now burns half of the six billion tons of coal used globally each year.