Glossary

Biomass: Generally includes plant materials, such as crops, crop residues, algae, wood waste materials from timbering and lumbering operations, construction and demolition waste, municipal solid waste and sewage sludge (or biosolids). The specific definition of biomass can depend upon state laws or regulations.

Biomass Gasification: The conversion of biomass or biosolids (sewage) into a gas that can be used to produce electricity and products. Biomass gasification differs in several aspects from traditional gasification. The plants are generally smaller in scale, use air instead of oxygen (or use plasma gasification) and require that the biomass be dried before being gasified.

Btu: British thermal unit. Btu is a measure of the heating value of a fuel. It is the amount of heat required to raise one pound of water one degree Fahrenheit at atmospheric pressure. The higher the number of Btu's per pound of feedstock, the higher the heating value. For example, the heating value of bituminous coal is typically 10,000-12,500 Btu per pound, while municipal solid waste is in the range of 4,000-5,500 Btu per pound. Gasifiers are typically designed or rated by the heat input in Btu per hour.

Carbon Capture: Separating out the carbon dioxide (CO2) and concentrating it so that it can be compressed, transported and stored. CO2 capture technologies are commercially proven. Gasification plants manufacturing ammonia, hydrogen, fuels or chemical products routinely capture CO2 as part of their process. See more about CO2 capture on the Gasification and CO2 page.

Combustion: Burning or incineration of a fuel using excess air or oxygen. When carbon-based materials (like coal or biomass) are combusted, the reaction produces carbon dioxide and heat, in addition to criteria air pollutants. Gasification is a different type of process, producing a gas. It is not combustion and provides a less costly means of capturing CO2.

Criteria Air Pollutants: Under the authority of the Clean Air Act, the U.S. Environmental Protection Agency has established ambient air quality standards for common air pollutants, such as carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. EPA regulates these air pollutants on the basis of information (criteria) on the health and/or environmental impacts of these pollutants. Criteria pollutants are the only air pollutants with national ambient air quality standards that define the allowable concentrations of these substances in the air.

Feedstock: The material fed into a gasifier and converted into a synthesis gas (syngas). Any carbon-containing material, (solid, liquid or gas), can be used as a feedstock for a gasifier. Traditional feedstocks include coal and petroleum coke (or other residues of petroleum refining). In addition, biomass, biosolids, municipal solid waste, industrial wastes, and natural gas are used as feedstocks. The feedstock itself is not a "fuel" in gasification, since it is not combusted. Rather, it is converted into a gas (syngas), which has value as hydrogen, or transportation fuels that can then be combusted externally.

Gasification: Gasification is a thermo-chemical process that converts carbon-containing materials, such as coal, petroleum coke (petcoke), biomass, waste, or other materials, with little or no oxygen present and at high temperatures, into a synthesis gas (syngas). The syngas can then be used, to produce electric power, and valuable products such as chemicals, fertilizers, substitute natural gas, hydrogen, steam, and transportation fuels. Gasification is very different from combustion, in that the carbon-containing materials (feedstocks) are not burned or incinerated; they are converted into the syngas. Read more at the Gasification Process page.

Gasifier: A vessel where the gasification reactions take place. In the gasifier, the feedstock reacts with oxygen (or air) and water (or steam) at high temperatures. Temperatures in gasifiers range from 900-3,000 degrees Fahrenheit, depending technologies. Under these conditions, the gasifier breaks apart the chemical bonds of the feedstock, forming syngas.

Integrated Gasification Combined Cycle (IGCC): An IGCC power plant combines the gasification process with an efficient "combined cycle" power generator (consisting of one or more gas turbines and a steam turbine). Clean syngas is combusted in the gas turbines to generate electricity. The excess heat from the gasification reactions r is then converted into steam. This is combined with steam produced from the gas turbines, and sent to a steam turbine generator to produce additional electricity. Read more at the Products and Applications page.

Industrial gasification: Large scale gasification operations used by industry, such as the chemical, paper, and fertilizer industries. Typical products from industrial gasification are gases, chemicals, fertilizers, and transportation fuels. Read more at the Products and Applications page.

Municipal solid waste (MSW): Residential and commercial materials that are used and then discarded. These materials include paper, yard waste, food waste, and containers (such as plastic bottles and cans), tires and electronics. MSW may include recyclable materials, depending on the amount of recycling provided by the local government.

Partial oxidation: Partial oxidation is a chemical reaction. It occurs in a limited oxygen environment - in a pressurized vessel with heat, feedstock (such as coal) and limited oxygen creating a syngas consisting primarily of hydrogen and carbon monoxide.

Plasma: Often called the fourth state of matter (the other three are solid, liquid, and gas). Plasma is created when an electrical charge passes through a gas. The resultant "flash" of lightning is an example of plasma found in nature.

Plasma gasification: The use of plasma, generally in the form of a plasma "torch" or "arc" to provide the heat energy needed to initiate a gasification reaction. Plasma torches and arcs can reach temperatures of 5,000 - 10,000 degrees Fahrenheit. The most typical use of plasma gasification is to convert various materials, such as municipal solid waste and hazardous waste, into a clean syngas used to produce electricity and other products.

Slag: A glass-like byproduct of the gasification process. Slag is carbon or inert material such as ash that was not converted to synthesis gas in the gasifier. It is inert, non-hazardous and can be used in roadbed construction, roofing materials and other applications.

Syngas or synthesis gas: The gas produced as the result of the gasification reactions of feedstock, oxygen (or air) and water (or steam). Syngas consists primarily of hydrogen and carbon monoxide. Depending on the type of gasification technology, quantities of nitrogen, methane, carbon dioxide, hydrogen sulfide and water vapor are also present in the syngas. These can be removed and reused using conventional gas cleaning processes.

Waste- to-Energy gasification: The process of using gasification to convert various types of waste streams, such as municipal solid waste, hazardous wastes or other industrial and commercial wastes into a synthesis gas that can be used to produce electricity and other valuable products. This differs from burning or incinerating the waste, which involves combustion, not gasification. Combustion produces carbon dioxide and heat, but not the syngas produced by gasification.

Information with thanks to the "Gasification Technologies Council"

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