Clean Coal

clean coal

In the United States, clean coal is any technology that may reduce emissions of carbon dioxide and other greenhouse gasses that arise from the burning of coal for electrical power. Typically, the term clean coal is used by coal companies in reference to carbon capture and storage (CCS), which pumps and stores emissions underground, and to plants using an Integrated gasification combined cycle (IGCC), which is technology that turns coal and other carbon based fuels into synthesis gas (‘syngas,’ which can be used to produce diesel, or converted into methane or other fuels).

Historically, the term has been used to refer to technologies for reducing emissions of ash, sulfur, and heavy metals from coal combustion. Carbon capture and storage technologies are being developed primarily in response to regulations by the EPA—most notably the ‘Clean Air Act’—and in anticipation of legislation that seeks to mitigate climate change. Currently, the electricity sector of the United States is responsible for about 41% of the nation’s carbon dioxide emissions, and half of the sector’s production comes from coal-fired power plants.

The US Department of Energy works with private industry to develop CCS technologies. Several methods are available under this technology including pre-capture, oxy-fuel combustion, and post-capture CCS. Perhaps the most popular example of a coal-based plant using (oxy-fuel) carbon-capture technology is Vattenfall’s Schwarze Pumpe plant in Germany. However, it has not yet been demonstrated that carbon stored underground will be able to stay there indefinitely. Another problem is that for every ton of coal that is burned, 2.93 tons of carbon dioxide is created, meaning that for every train bringing coal to a CCS coal plant, three trains would be needed to remove the CO2.

A more recent technology being co-developed by Babcock-ThermoEnergy is the Zero Emission Boiler System (ZEBS). This system features near 100% carbon-capture and according to company information virtually no air-emmissons. Other carbon capture and storage technologies include those that dewater low-rank coals. Low-rank coals often contain a higher level of moisture content which contains a lower energy content per ton. This causes a reduced burning efficiency and an increased emissions output. Reduction of moisture from the coal prior to combustion can reduce emissions by up to 50 percent.

The UK government’s Department for Energy and Climate Change (DECC) is working towards a clean energy future and supports clean coal projects across the country. In 2010 UK based company B9 Coal announced a clean coal project with 90% carbon capture to be put forward to DECC in order to help the UK raise it’s profile among green leaders across the world. This proposed project gasifys coal underground and processes it to create pure streams of hydrogen and carbon dioxide. The hydrogen is then used as an emissions free fuel to run an alkaline fuel cell whilst the carbon dioxide is captured.

According to the United Nations Intergovernmental Panel on Climate Change, the burning of coal, a fossil fuel, is a significant contributor to 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. Sequestration technology has yet to be tested on a large scale and may not be safe or successful. Sequestered carbon dioxide may eventually leak up through the ground, may lead to unexpected geological instability or may cause contamination of aquifers used for drinking water supplies. There are also concerns that plans to pump some of the sequestered CO2 into certain oil and gas reserves, to help make the fuels easier to pump out of the ground, will lead to increased concentrations of CO2 in potential fuel supplies. This would have to be removed or released during the refining process. Technologies related to reducing the environmental impact of extracting energy from coal do not address environmental impacts of coal mining. Examples of environmental impacts of coal mining include the Kingston Fossil Plant coal fly ash slurry spill.

The byproducts of coal combustion are considerably hazardous to the environment if not properly contained. While it is possible to remove most of the sulfur dioxide, nitrogen oxides, and particulate matter (PM) emissions from the coal-burning process, carbon dioxide emissions and radioactive isotopes will be more difficult to address. Coal-fired power plants are the largest aggregate source of mercury: 50 tons per year come from coal power plants out of 150 tons emitted nationally in the USA and 5000 tons globally. In the US, neither the combustion products of oil, nor their associated solid or liquid waste streams, are considered to be major contributors to mercury pollution.

Whether carbon capture and storage technology is adopted worldwide will ‘…depend less on science than on economics. Cleaning coal is very expensive.’ Credit Suisse Group says $15 billion needs to be invested in CCS over the next 10 years for it to play an important role in climate change. The International Energy Agency says $20 billion is needed. The Pew Center on Global Climate Change says the number is as high as $30 billion. Those figures dwarf the actual investments to date. In the US, the Bush administration spent about $2.5 billion on clean coal technology. The ‘American Reinvestment and Recovery Act,’ signed in 2009 by President Obama, allocated $3.4 billion for advanced carbon capture and storage technologies, including CCS demonstration projects.

Environmentalists such as Dan Becker, director of the Sierra Club’s ‘Global Warming and Energy Program,’ believes that the term ‘clean coal’ is misleading: ‘There is no such thing as clean coal and there never will be. It’s an oxymoron.’ The Sierra Club’s ‘Coal Campaign’ has launched a site refuting the clean coal statements and advertising of the coal industry. Complaints focus on the environmental impacts of coal extraction, high costs to sequester carbon, and uncertainty of how to manage end result pollutants and radioactive material. Paleontologist and influential environmental activist Tim Flannery made the assertion that the concept of clean coal might not be viable for all geographical locations. Critics also believe that the continuing construction of coal-powered plants (whether or not they use carbon sequestration techniques) encourages unsustainable mining practices for coal, which can strip away mountains, hillsides, and natural areas. They also point out that there can be a large amount of energy required and pollution emitted in transporting the coal to the power plants. The ‘Reality Coalition,’ a green nonprofit organization, ran a series of television commercials in 2008 and 2009. The commercials were highly critical of clean coal, stating that without capturing carbon dioxide emissions and storing it safely that it cannot be called clean coal.

‘Clean coal’ was an umbrella term used to describe methods that have been developed to reduce the environmental impact of coal-based electricity, which accounts for nearly half of the United States’ electricity supply. These efforts include chemically washing minerals and impurities from the coal, gasification, treating the flue gases (gas exiting to the atmosphere via a flue) with steam to remove sulfur dioxide, carbon capture and storage technologies to capture the carbon dioxide from the flue gas, and coal de-watering technologies to improve the energy quality and thus the efficiency of burning coal for energy. Figures from the EPA show that these technologies have made today’s coal-based generating fleet 77 percent cleaner on the basis of regulated emissions per unit of energy produced.

While the term ‘clean coal’ is today commonly used to describe carbon capture technologies, the earliest use of the term can be traced back to U.S. Senate Bill 911 in 1987: ‘The term clean coal technology means any technology…deployed at a new or existing facility which will achieve significant reductions in air emissions of sulfur dioxide or oxides of nitrogen associated with the utilization of coal in the generation of electricity.’ And before that, in a speech to mine workers in 1918; at that time, clean coal referred only to mining of coal ‘free of dirt and impurities.’ In the early 20th century, prior to World War II, clean coal (also called ‘smokeless coal’) referred to anthracite and high-grade bituminous coal, used for cooking and home heating.

It was in the late 1980s and early 1990s that the U.S. Department of Energy (DOE) conducted a joint program with the industry and State agencies to demonstrate these technologies large enough for commercial use. The program, called the ‘Clean Coal Technology & Clean Coal Power Initiative,’ has had a number of successes that have reduced emissions and waste from coal-based electricity generation. Moreover, the Program has met regulatory challenges by incorporating nitrogen oxide control technologies ‘into a portfolio of cost-effective regulatory compliance options for the full range of boiler types.’ This portfolio has positioned the U.S. as a top exporter of clean coal technologies such as those used for nitrogen oxide.

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