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Clean coal technology is a collection of technologies being developed to mitigate the environmental impact of coal energy generation. When coal is used as a fuel source, the gaseous emissions generated by the thermal decomposition of the coal include sulphur dioxide, nitrogen dioxide, carbon dioxide, and other chemical byproducts that vary depending on the type of the coal being used. These emissions have been established to have a negative impact on the environment, contributing to acid rain and climate change. As a result, clean coal technologies are being developed to remove or reduce pollutant emissions to the atmosphere. Some of the techniques that would be used to accomplish this include chemically washing minerals and impurities from the coal, gasification (see also IGCC), treating the flue gases with steam to remove sulfur dioxide, carbon capture and storage technologies to capture the carbon dioxide from the flue gas and dewatering lower rank coals (brown coals) to improve the calorific value, and thus the efficiency of the conversion into electricity.
Clean coal technology usually addresses atmospheric problems resulting from burning coal. Historically, the primary focus was on sulfur dioxide and particulates, since it is the most important gas in the causation of acid rain. More recent focus has been on carbon dioxide (due to its impact on global warming) as well as other pollutants. Concerns exist regarding the economic viability of these technologies and the timeframe of delivery, potentially high hidden economic costs in terms of social and environmental damage, and the costs and viability of disposing of removed carbon and other toxic matter.
Coal, which is primarily used for the generation of electricity, is the second largest domestic contributor to carbon dioxide emissions in the USA. The public has become more concerned about global warming which has led to new legislation. The coal industry has responded by running advertising touting clean coal in an effort to counter negative perceptions and claiming more than $50 billion towards the development and deployment of "traditional" clean coal technologies over the past 30 years; and promising $500 million towards carbon capture and storage research and development.
The world's first "clean coal" power plant went on-line in September 2008 in Spremberg, Germany. The plant is owned by the Swedish company Vattenfall and has been built by the German firm Siemens. The plant is called Schwarze Pumpe power station. The facility captures CO2 and acid rain producing sulfides, separates them, and compresses the CO2 into a liquid. Plans are to inject the CO2 into depleted natural gas fields or other geological formations. This technology is considered not to be a final solution for CO2 reduction in the atmosphere, but provides an achievable solution in the near term while more desirable alternative solutions to power generation can be made economically practical.
According to United Nations Intergovernmental Panel on Climate Change, the burning of coal, a fossil fuel, is a major contributor to global warming. (See the UN IPCC Fourth Assessment Report). As 25.5% of the world's electrical generation in 2004 was from coal-fired generation (see World energy resources and consumption), reaching the carbon dioxide reduction targets of the Kyoto Protocol will require modifications to how coal is utilized.
Some in the coal industry[who?] and the U.S. Department of Energy[who?] refer to carbon capture and sequestration (CCS) as the latest in "clean coal" technologies. The "clean coal" terminology is generally not endorsed by professionals in CCS, and is actively opposed by environmental organizations that favor CCS. CCS is a means to capture carbon dioxide from any source, compress it to a dense liquid-like state, and inject and permanently store it underground. Currently, there are more than 80 carbon capture and sequestration projects underway in the United States. All components of CCS technology have been used for decades in conjunction with enhanced oil recovery and other applications; commercial-scale CCS is currently being tested in the U.S. and other countries.[by whom?] Proposed CCS sites are subjected to extensive investigation and monitoring to avoid potential hazards, which could include leakage of sequestered CO2 to the atmosphere, induced geological instability, or contamination of aquifers used for drinking water supplies.
Supporters[who?] of clean coal use the Great Plains Synfuels plant to support the technical feasibility of carbon dioxide sequestration. Carbon dioxide from the coal gasification is shipped to Canada where it is injected into the ground to aid in oil recovery. Supporters[who?] admit that carbon sequestration is expensive.