Worlds of David Darling
Encyclopedia of Science
Home > Encyclopedia of Alternative Energy


A major fossil fuel. Although widely considered a dirty and antiquated source of energy, coal still has an important role to play in the global energy mix because of its widespread availability and stable price. According to the World Coal Institute, proven reserves of coal in 2005, based on current production levels were 164 years, compared with 67 years for gas and 41 years for oil. The hope among politicians and industry experts is that the development of "clean coal technology" will make the fuel environmentally acceptable.

Figures released by the International Energy Agency (IEA) in 2005 projected coal use to rise by 1.4% a year until 2030, when annual demand will reach nearly 7.3 billion ton – almost one billion ton more than present levels. This growth in demand is being driven by emerging economies. China, in particular, is building new coal-fired power stations at an unprecedented rate.

Clean coal technology (CCT)

CCT includes all the various strands of research and development aimed at improving the environmental performance of coal-fired plants. It's generally taken to mean the process by which coal is gasified (i.e. turned into a gas as opposed to the conventional method of burning the coal itself in a combustion boiler), burned to power a turbine, and the carbon dioxide and other emissions captured for storage away from the atmosphere. However, the efficiency of traditional boilers used in coal stations has also been steadily improving and can rival the efficiency of gasification plants.

Improving the efficiency of boilers used in coal-fired power stations cuts carbon dioxide emissions because less coal is needed to generate the heat energy that turns the steam turbines powering the electricity generators. Current systems, called advanced supercritical boilers, have an efficiency level of around 42% compared with the 30% efficiency of an old-style boiler. The latest boilers also allow biomass to be added to the fuel mix, which can further reduce emissions. Increase the efficiency of a plant and combining it with biomass/coal firing reduces emissions to a level similar to that as a gas-fired power plant.

Gasification systems, such as Integrated Gasification Combined Cycle (IGCC), can be used for poly-generation. This allows the gas (hydrogen) to be used either to power a gas turbine or to be piped elsewhere, for example in transport or in the chemical industry. This approach could become a key component role in a future hydrogen economy.

Most of the industrialised nations are investing a significant amount of money into research and development of clean coal technology. Japan, Australia and the EU all have their own CCT programs. The biggest is the US FutureGen program, a $1bn project that is attempting to demonstrate the commercial viability of near-zero emission coal-fuelled power. It will look at integrating an IGCC electricity plant with hydrogen production, carbon dioxide capture, and geological storage.

Related categories

   • FUELS