WASTE POWER GENERATION TECHNOLOGIES
A power-from-waste plant (also commonly known as a waste-to-energy or WTE plant) is a power station fueled with urban waste. As already indicated, such a facility may have as its primary function waste disposal. Nevertheless, the technologies employed will be traditional power generation technologies as used in combustion plants. Combustion systems include grate burners, some fluidized-bed burners, and more recently gasification and pyrolysis. Heat generated in these combustion systems is used to raise steam and drive a steam generator.
Within the broad outline above, power-from-waste plants vary enormously. Much depends on the waste to be burned, its energy content, the amount of recyclable material or metal it contains, and its moisture content. Waste may be sorted before combustion or it may be burned as received. Emission control systems will vary too, with toxic metals and dioxins a particular target, but nitrogen oxide, sulfur dioxide, other acidic gases, and carbon monoxide emissions must all fall below local limits. Carbon dioxide emissions may need monitoring to comply with greenhouse gas emission regulations.
Once the waste has been burned, residues remain. Power-from-waste plants will generally reduce the volume of waste to around 10% of its original. A way must then be found to dispose of this residual ash. If it is sufficiently benign, it may be used as aggregate for road construction. Otherwise, it will probably be buried in a landfill. Other residues from emission control systems will have to be buried in controlled landfill sites too.
Northern Europe has been the traditional home of waste incineration plants for power generation and it continues to house the largest concentration of such plants. Altogether there are around 440 WTE plants in the EU producing 30 TWh of electricity and 55 TWh of heat in 2009.4 Japan has also made extensive use of waste combustion, though not always for power generation, with around 100 plants in operation, while the United States has a similar number. In 2011 there were about 800 WTE plants in operation in 40 countries around the world. These plants were estimated to have treated 11% of MSW generated globally.
Europe has also developed the most widely used waste combustion technology based on waste incineration. Two companies, Martin GmbH based in Munich, Germany, and Swiss company Von Roll, accounted for close to 70% of the market for the dominant technology called mass-burn at the end of the 20th century.5 The rest of the market is divided among a number of smaller companies, mostly based in either Europe, the United States, or Japan. The dominant European technology has also been widely licensed. It was the source of the technology used in most U.S. power-from-waste plants built in the late 1970s and early 1980s. More recently several developing countries of Asia have taken interest in power-from-waste and European technology has been modified for use in China, for example.
At the same time newer technologies based on gasification and pyrolysis are being developed by a variety of companies. These are based on technologies from other industries such as petrochemicals.