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Anthracite is a type of coal that has the highest carbon content and the lowest moisture and ash content. Anthracite burns slowly and makes a good heating fuel for homes.


Bituminous is a type of coal that contains very little moisture and has high heat value. It is used to generate electricity and to produce coke, a coal residue used in the steel industry. Bituminous coal is the most plentiful type in the United States.


Btu is an abbreviation for British thermal unit, the standard for measuring the energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Cap and Trade

Cap means there is a 'set ceiling' on the total amount of certain greenhouse gases that can be emitted from factories, power plants and other installations in the country. Companies receive emission allowances which can be sold or bought from one another as needed. One allowance is equivalent to each tonne of CO2 that a holder is allowed to emit. At the end of each year, each company must surrender enough allowances to cover all its emissions. If a company has excess allowances it can sell it to its peers who are short of allowances. The EU ETS has put a price on carbon emissions and shown that it is possible to trade in greenhouse gas emissions. Thus 'Cap and Trade' provides a platform for carbon trading.

Carbon capture and storage

The practice of capturing CO2 emitted from industries (especially power plants) and sequester in geological formations like depleted oil & gas fields, coal bed methane and saline aquifers is known as carbon capture and storage. There are different methods of capturing carbon dioxide. They are pre-combustion, post-combustion and oxy fuel method. The captured CO2 is compressed to liquid form and transported through pipelines and tankers to the sequestration site. The captured CO2 can also be used in the manufacturing of products like cement, gasoline, plastics, methanol and other chemicals.

Carbon Cycle

The biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere, and atmosphere of the earth is termed as carbon cycle. The movement of carbon and the exchanges between the different reservoirs occurs due to chemical, physical and biological processes.

Carbon Offset
Carbon offset refers to set of activities or processes that offset or mitigate the amount of greenhouse gases emitted into the atmosphere. The options available for carbon offset are carbon capture and sequestration using CCS technologies, planting of trees in large numbers and adopting renewable energy resources.

Carbon Sink

A carbon sink is a reservoir that store carbon containing compounds like carbon dioxide for an indefinite period thereby offsetting carbon emissions. There are two types of carbon sinks-natural and artificial. Artificial sinks are those created by man to capture and store carbon dioxide to prevent the accumulation of the same in the environment. Examples of artificial carbon sinks are underground geological formations like depleted oil and gas fields, coal bed methane and saline aquifers, while terrestrial plants and trees that absorb CO2 through the process of photosynthesis is a perfect example for natural carbon sinks.

Carbon Trading

Carbon trading is a mechanism that involves trading in carbon permits as a part of a initiative to reduce carbon emissions. Trading involves buying or selling of carbon permits in the open market. Firms are given certain allowance for carbon emissions into the atmosphere. When they exceed their legally permitted limit, these firms are bound to buy carbon permits from the market. The organizations that don't use their full quota can trade the excess quantity in the market. This provides a financial incentive to those organizations that are very keen on reducing their carbon emissions and thereby contributing to the reduction of greenhouse gases in the atmosphere.

Certified Emission Reduction (CER)

CER's are carbon credits issued by CDM executive board for the CDM projects aimed at reducing greenhouse gases in the atmosphere. One CER is equivalent to 1 ton of CO2 avoided. CERs can be held by private entities or governmental organizations in electronic accounts with the United Nations.

Clean Air Act

The Clean Air Act is a strict air pollution control law that was passed in the USA in 1970.

Clean Development Mechanism

CDM stands for Clean Development Mechanism which is a mechanism defined in Article 12 of the Kyoto protocol to achieve the following objectives. To assist countries developing countries) in contributing to the sustainable development which is to prevent climate change. 2. To assist Annex I countries in achieving compliance with their greenhouse gas reduction commitment. Under CDM, the developed countries that have a commitment to reduce greenhouse gas emissions under Kyoto protocol can invest in green projects in developing countries. In this process they can claim the carbon credits equivalent to the reduction in the amount of CO2 emissions.

Clean Coal Technology (CCT) program

The CCT program refers to a number of technological advances that make the burning process of coal cleaner by removing pollutants such as sulfur, nitrogen, and fly ash that can contaminate the air and water.

Climate Change

Change in average temperature of earth's surface is termed as climate change. Climate change is a natural phenomenon but post the industrial revolution period, human activity is cited as the important trigger for change in climatic condition on the earth. Anthropocentric activities increase the greenhouse gas concentration in the atmosphere that traps more amount of heat, leading to global warming and thus contributing to climate change. Some of the consequences of climate change predicted by researchers are:
1. Melting of glaciers and thereby increase in mean sea level
2. Submergence of coastal areas
3. Increased risk of droughts, and floods
4. Disappearance certain species of plants and animals

CO2 Scrubber

CO2 scrubber is a device used to remove carbon dioxide from waste streams of industries to prevent it from entering atmosphere. Some of the methods of carbon dioxide scrubbing are Absorption Algae based carbon capture Solvents and sorbents Afforestation Activated carbon


Coal is a burnable carbonaceous rock that contains large amounts of carbon. Coal is also a fossil fuel—a substance that contains the remains of plants and animals and that can be burned to release energy. Coal contains other elements such as hydrogen, oxygen, and nitrogen; has various amounts of minerals; and is itself considered to be a mineral of organic origin.

Coal gasification

Coal gasification is the process that changes coal into a gas that has the same heating value as natural gas and that is cleaner than burning coal itself.


Cogeneration is a single process that produces both heat and power simultaneously. This is a highly efficient process producing electricity and heat from the same energy source. Thermal energy produced in the system can be used directly for certain applications or indirectly to produce steam, hot air for drying or chilled water for process cooling. Some of the benefits of cogeneration are as follows: Increased efficiency of energy conversion. Lower emission of greenhouse gases mainly CO2. Large cost savings, providing additional competitiveness for industrial and commercial users while offering affordable heat for domestic users also. Provides an opportunity to move towards decentralized forms of electricity generation.


Coke is a substance made by heating coal to very high temperatures. Coke is used in the iron and steel industry.

Combined-cycle system

In a combined-cycle system, gas from heating coal operates a combustion turbine connected to a generator, and the exhaust gases from this turbine heat water that, in turn, operates a steam-powered generator.

Continuous miner

A continuous miner is a machine with large, rotating cutters that break into the coal and with arms that scoop the coal onto a built-in conveyor.

Deep Mining

See Underground mining.

Electrostatic precipitator

An electrostatic precipitator is a device that gives coal dust particles an electric charge so they can be attracted to a collector plate. Electrostatic precipitators help prevent air pollution.


A flue is a pipe through which gases and smoke escape from burning coal.

Flue gas desulfurization system

A flue gas desulfurization system, or scrubber, is a device that removes more than 90 percent of the sulfur dioxide emissions from the burning process of coal.

Fluidized-bed combustion (FBC)

FBC is a process of burning coal in which the coal is inserted in a bed of particles that are suspended in the air and that react with the coal to heat the furnace more cleanly. In FBC, coal is burned at a slightly lower temperature, which helps prevent some nitrogen oxide gases from forming.

Fly ash

Fly ash refers to the fine particles contained in the gases that are released when coal is burned.

Fossil fuel

A fossil fuel is a fuel formed from the remains of organic materials. Fossil fuels include coal, oil, and natural gas.


A generator is a machine that turns mechanical energy into electric energy.


Igneous is one of three types of rock. Igneous rock forms when magma, molten rock material within the earth, forces its way to the surface and cools.

Land reclamation

Land reclamation is the process of protecting, restoring, and possibly even improving the land before, during, and after surface mining. As coal is removed from one section of a surface mine, the land at another part is returned, regraded, and replanted. In the end, this means that the land is preserved, nature has been protected, water and soil are conserved, and the land can be turned into productive farmland, forests, and lakes.


Lignite is a type of coal that contains a lot of moisture and ash and breaks apart easily. Of the four types, lignite has the lowest carbon content and heating value. Also called brown coal, lignite is used mainly at electricity-generating plants.

Longwall mining machine

A longwall mining machine is a cutting machine that works along walls of coal up to 1,000 feet long to cut coal and drop it onto a conveyor belt.


Metamorphic is one of three types of rock. Metamorphic rock is rock whose minerals and texture have been changed by high temperatures, water, and pressure.

Nonrenewable energy

Nonrenewable energy is the energy supplied by fossil fuels—coal, oil, and natural gas. Fossil fuels are limited in supply.


Overburden is the material that is removed from the earth's surface to uncover the coal. Overburden includes layers of earth and rock.


Peat is a soggy, spongelike material that forms from plants and trees after they die. Peat from plants and trees that died about 300 million years ago became buried and compressed under the earth's surface over a long period of time. Over millions of years and through the forces of heat and pressure, the compressed peat became coal.

Recoverable coal

Recoverable coal refers to the amount of coal that can be removed. There are approximately 275 billion tons of recoverable coal reserves in the United States.


Sedimentary is one of three types of rock. Sedimentary rock forms from mineral fragments deposited by wind, water, or glaciers.


Sludge is the muddy waste that is produced during processes to remove sulfur from coal.


A slurry is coal that is ground to a powder and mixed with water. In this form, coal can be pumped through a pipeline.

Slurry pipeline

A slurry pipeline is a pipeline that transports coal that has been ground to a powder and mixed with water. A coal slurry pipeline connects a mine in Arizona with a power plant in Nevada.


Subbituminous is a type of coal that is dull black and has less moisture than lignite. Subbituminous is generally used to produce steam for electricity generation. Reserves of subbituminous coal are found mostly in western states and Alaska.

Surface mining

Surface mining is used when coal is found close to the surface or on hillsides. It involves removing the topsoil and subsoil and setting them aside while the coal is removed.

Surface Mining Control and Reclamation Act (SMCRA)

The SMCRA, enacted in the late 1970s, is the first comprehensive national surface-mining law. Under the law, each state that establishes federally approved enforcement programs has the primary responsibility for enforcing mining regulations in the state. If a state lacks these programs, the Office of Surface Mining Reclamation and Enforcement in the U.S. Department of Interior implements the federal law.


A turbine is an engine that spins around, causing the heat energy of burning coal to become mechanical energy.

Underground mining

Underground mining is used to extract coal that is deep beneath the surface or in seams exposed on hillsides. It involves drilling two openings called shafts into the coal bed—one to transport miners and equipment and the other to bring coal to the surface.

Carbon Capture

The process of separating relatively pure carbon dioxide gas as a byproduct of industrial processes (including synthetic ammonia production, hydrogen production and limestone calcination) and electricity generated from fossil fuels, such as coal and natural gas.

Clean Coal Technology

Technologies – both pre- and post-combustion – that improve the environmental performance of coal-based electricity plants. Many of these technologies increase the operational efficiency of power plants, as well as reduce emissions.

Carbon dioxide (CO2)

A colorless, odorless, nonpoisonous gas that is a normal part of Earth's atmosphere. It is an unavoidable product of the combustion of carbon in fossil fuels (hydrocarbons) and biomass (carbohydrates). Carbon dioxide is a greenhouse gas, along with water vapor, methane and others such as chlorofluorocarbons.

Coal Gasification

The process of converting coal into synthetic gas by a process using incomplete combustion to create carbon monoxide (CO). The CO is transformed into a substitute natural gas through chemical interaction with a catalyst for use as a fuel or further processing and concentration into an industrial feedstock or liquid fuel.

Carbon Sequestration

The fixation (or storage) of carbon dioxide in a geologic or biologic sink.

Flue Gas

Emissions from fossil fuel combustion that are directed into the atmosphere through a chimney or stack. In power plants, the flue gas first is directed through a series of devices designed to rid the gases of specific pollutants (e.g., sulfur dioxide, nitrogen oxides, particulate matter and mercury) before the flue gas is released into the atmosphere.


A private-public partnership to design, build and operate the world's first coal-fueled, near-zero emissions power plant. The facility's design is intended to support the testing of commercial-scale carbon capture and sequestration.

Greenhouse Gas

Any one of a group of gases such as carbon dioxide, methane, water vapor (clouds) and a variety of man-made chemicals that trap the sun's radiant energy and prevent it from passing back out through Earth's atmosphere and into space.

Integrated Gasification Combined Cycle (IGCC)

A technology for generating electricity that utilizes coal gasification to produce a synthesis gas. The "syngas" undergoes a cleaning process that removes particulate matter and sulfur compounds. The gas is then converted into electricity using a combustion turbine. Waste heat from the gasification process is utilized by additional turbines to generate supplemental electricity (a combined cycle), thereby increasing the efficiency by which coal is converted into electricity. The process integrates coal gasification with a combined cycle.

Nitrogen Oxides (NOx)

Compounds of nitrogen and oxygen produced by the combustion of fossil fuels.

Particulate Matter

Very small particles of solid or liquid matter that remain dispersed in the atmosphere. PM can be aerosol, dust, fumes, mist, smoke or spray.

Pilot Project

An activity planned as a test or trial.


Post-combustion technology that utilizes a chemical reaction to remove air pollutants, typically sulfur dioxide present in flue gas, prior to release into the atmosphere.

Sulfur Oxides (SOx)

Compounds containing sulfur and oxygen, such as sulfur dioxide (SO2), created when coal is combusted.

Clean Coal Acronyms

ARD&D - Analysis, Research, Development, and Demonstration

ASU - Air Separation Unit

BACT - Best Available Control Technology

CAIR - Clean Air Interstate Rule

CAMR - Clean Air Mercury Rule

CCS - Carbon Capture and Storage

CFB - Circulating Fluid Bed

CGE - Computable General Equilibrium

COE - Cost of Electricity, ¢/kWe-h

CSLF - Carbon Sequestration Leadership Forum

EPPA - Emissions Prediction and Policy Analysis Model

EPRI - Electric Power Research Institute

ESP - Electrostatic Precipitator or Precipitation

FGD - Flue Gas Desulfurization

F-T - Fischer-Tropsch

GHG - Greenhouse Gas

HHV - Higher Heating Value, kJ/kg

HRSG - Heat Recovery Steam Generator

ICE - Injectivity, Capacity and Eff ectiveness

IECM - Integrated Environmental Control Model

IGCC - Integrated Gasifi cation Combined Cycle

LAER - Lowest Achievable Emissions Rate

LLV - Lower Heating Value, kJ/kg

MMV - Measurement, Monitoring, and Verifi cation

NAAQS - National Ambient Air Quality Standards

NPV - Net Present Value

O & M - Operating and Maintenance Costs, ¢/kWe-h

PC - Pulverized Coal

PDU - Process Demonstration Unit

PM - Particulate Matter

PRB - Powder River Basin

RD&D - Research, Development, and Demonstration

SC - Supercritical

SCPC - Supercritical Pulverized Coal

SCR - Selective Catalytic Reduction

SNCR - Selective Non-Catalytic Reduction

SUBC - Subcritical

TCR - Total Capital Required, $/kWe

TPC - Total Plant Cost, $/kWe

USC - Ultra-Supercritical