But it's also one of the dirtiest with the world's 2,300 coal-fired power stations contributing around 40 percent of all man-made emissions, according to the World Coal Institute. Their continued use enrages many environmentalists who argue that we should be phasing coal out. But the coal industry is pinning its hopes on the rather oxymoronic-sounding "clean coal," which has become the umbrella term for a range of new technologies that share the aim of cleaning up coal in the 21st century. Earth's Frontiers takes a look at the options:

The Second International Exhibition of Energy Efficiency and Environment Hanoi (ENTECH Hanoi 2010), a large exhibition of this kind for the north will be held from May 27-30 at the Giang Vo Exhibition Center in Hanoi.

According to Nguyen Trong Thu, the secretary general of the Bat Trang Ceramics Association, there used to be about 700 traditional coal kilns that were in continuous operation, which caused serious environment pollution.

New energy-saving products and technologies used in daily life are gaining in popularity. CCTV reporter takes us to the Beijing International Energy Saving and Environmental Protection Exhibition to show us the latest in green technology.