The familiar building material cement is a growing source of CO2 emissions, especially in the developing world, where the demand for roads, dams, and housing is intense. The chemical reaction that creates cement—the binding agent that holds stones and sand together to make concrete—releases large amounts of carbon dioxide. And creating that reaction involves heating the materials to 1,500°C (about 2,700°F). That takes a lot of energy, much of which is generated by coal.
Cleaning Up Cement
China accounts for half of world cement consumption. But cement-manufacturing plants in the developing world tend to be newer, more efficient and therefore less CO2-emitting than those in North America, for example.