Clean coal technology is an umbrella term used to
describe technologies being developed that aim to reduce the environmental
impact of coal energy generation. These include chemically washing minerals and
impurities from the coal, gasification, treating the flue gases with steam to
remove sulfurdioxide, 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 onsulfur 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, as well as by putting more than $50 billion towards the development
and deployment of clean coal technologies, including carbon capture
and storage. The expenditure has been unsuccessful to date in that there is not
a single commercial scale coal fired power station in the US that captures and
stores more than token amounts of CO2.
The world's first "clean
coal" power plant went on-line in September 2008 in Spremberg, Germany. The plant is state-owned and has been
built by the Swedish firm Vattenfall. The plant
is state owned because of the high costs of this technology, since private
investors are only willing to invest in other sources such as nuclear, solar
and wind. The facility captures CO2 and acid rain producing sulfides, separates them, and compresses the CO2 into a
liquid state. 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 the United
Nations Intergovernmental Panel on Climate Change, the burning of coal, a
fossil fuel, is a major contributor to climate change and global warming. As
25.5% of the world's electrical generation in 2004 was from coal-fired
generation, reaching the carbon dioxide reduction targets of the Kyoto Protocol
will require modifications to how coal is utilized.
Some in the coal industry and
the U.S. Department of Energy refer to carbon capture and sequestration (CCS)
as the latest in"clean coal" power plant technologies. The
"clean coal" terminology is generally not endorsed by professionals
in CCS, and is actively opposed by environmental organizations that favorCCS. 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. 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 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
acknowledge that economics can be problematic for carbon sequestration.