Glossary: A to C
A-C | D-F | G-I | J-L | M-O | P-R | S-U | V-Z
A
Acid rain: Sulfur dioxide (SO2) and nitrogen oxides (NOx), along with other chemical compounds, are released during the combustion of fossil fuels. When these gases react in the atmosphere with water, oxygen, and other chemicals, they form acidic compounds. Sunlight increases the rate of most of these reactions. The resulting substances are wet (acid rain, snow, or fog) or dry (acidic gases or particulates) and may drift far from the original source before falling to the earth. The negative effects of these acidic deposits include damage to forests, soil, and aquatic ecosystems, damage to infrastructure and human health, and reduced visibility.
Ampere (amp): A unit of electrical current or rate of flow of electrons. One volt across one ohm of resistance causes a current flow of one ampere. Amperes are used by utilities and electrical engineers to measure electrical flow.
Anaerobic digestor gas: Anaerobic digestion is the breakdown of organic material without the use of oxygen (as opposed to aerobic digestion). When anaerobic digestion occurs, it produces gas that can be used to generate energy. The creation of landfill gas is a common form of anaerobic digestion.
Area network system: A section of the electrical grid typically found in small areas of major cities and designed to provide high reliability to a group of customers. An area network system, as opposed to a spot network or radial system, consists of multiple wires interconnected with each other and a group of customers. This provides multiple paths on which electricity can flow, to prevent loss of power if one piece of the network stops working. Because it is not currently possible to interconnect generation to an area network, clean energy development in these areas can be difficult.
B
Bioenergy: Energy or electricity produced using biomass as a fuel.
Biodiesel: Biodiesel is a type of biofuel made by combining animal fat or vegetable oil (such as soybean oil or recycled restaurant grease) with alcohol and can be directly substituted for diesel as a stand-alone fuel (called B100, for 100% biodiesel) or be used as an additive (called B20, for 20% bio-diesel). Biodiesel can be used in vehicles (newer cars, usually 1994 or later, are required for B100) and is beginning to be used in on-site electricity generation and heating applications.
Biofuel: Biofuels are renewable liquid fuels made from plant matter rather than fossil fuels. Today’s primary biofuels are ethanol and biodiesel. Biofuels can help reduce air toxics emissions, greenhouse gas buildup, and dependence on imported oil, while supporting United States agriculture.
Biomass: A type of renewable fuels that includes trees and other crops and residues, solid waste, sewage, and liquid fuels derived from agricultural products. Some of the common energy sources derived from biomass are landfill gas, anaerobic digester gas, methane, and biofuels including biodiesel, bio-oil, and ethanol. Biomass gasification is an emerging clean energy technology. See the Bioenergy section of the MTC website for more details.
Biomass gasification: This is a highly efficient process for converting woody biomass (wood chips, pellets, and other wood residues) into energy that can then be converted into electricity.
Bio-oil: Solid biomass can be converted into a carbon-rich liquid which can be used to produce chemicals and fuels. This liquid, or bio-oil, is produced through a process called pyrolysis, in which the biomass is broken down into liquid in an oxygen-free, high-temperature environment.
C
Carbon dioxide (CO2): Carbon dioxide is one of the most common greenhouse gases in the atmosphere and is regulated through the natural carbon cycle, where carbon dioxide is emitted into the air and reabsorbed by vegetation and water. This cycle is upset by the emission of additional carbon dioxide from human activities. Because natural cycles cannot absorb these additional emissions, a large portion of carbon dioxide remains in the atmosphere and increases climate change. The primary human source of carbon dioxide is the burning of fossil fuels for electricity, heat, and transportation.
Carbon monoxide (CO): This gas is created when the carbon in fossil fuels is not entirely burned during combustion and can have serious impacts on human health. The majority of carbon monoxide emissions come from the use of fossil fuels in transportation. Lesser quantities come from electricity production and natural events like forest fires. Improperly-adjusted gas stoves can also release high levels of indoor carbon monoxide. When released into the air, carbon monoxide can exacerbate heart disease and damage the human nervous system. Carbon monoxide also has an indirect effect on global climate change, and is a criteria pollutant.
Certified forest product: A forest product that is certified as sustainable/suitable for use in a green building is from a managed forest that has passed rigorous guidelines for responsible harvesting (rather than over-harvesting), ecosystem management and conservation, and long-term sustainable resource management. The Scientific Certification Systems’ Forest Conservation Program employs the principles of the Forest Stewardship Council to ensure that certified forests meet standards for sound forest management.
Chain-of-custody certification: A product certified through chain-of-custody has met certification requirements from production through distribution and sales. For a forest product, this means the wood has been extracted from the forest according to guidelines for sustainability, and that the process through which it is distributed to consumers is monitored to ensure that a product is certified as claimed. Learn more about chain-of-custody certification from Scientific Certification Systems.
Chemical energy: Chemical energy is generated from chemical reactions in which the chemical bonds of a substance are broken and rearranged to form new molecules that can provide energy. Chemical energy can be transformed into thermal energy, mechanical energy, and electrical energy. Respective examples of these conversions include burning wood, digestion of food, and the chemical process used in nuclear power plants.
Clean energy: Clean energy can be generally defined as energy from renewable sources such as biomass, wind, or solar power. The goal of clean energy is to have a low environmental impact, with low or zero emissions, and a minimal impact on the physical surroundings. Hydropower can be defined as clean energy due to zero emissions, but today's hydropower still often has substantial impacts on aquatic ecosystems. Waste-burning and wood-burning plants that capture emissions can be clean energy generators. Fossil fuels do not provide clean energy because of their emissions and environmental impacts. Learn more about clean energy technologies.
Coal: Coal is a fossil fuel that currently provides about half of the country’s electricity. Coal power plants create more emissions per unit of generated electricity than other fuels, and are required to install pollution control devices to curb pollution. Like natural gas and oil, coal is a nonrenewable resource because it cannot be replenished on a human time scale.
Compact fluorescent lamp (lightbulb): Compact fluorescent lamps (CFLs) use an advanced technology that uses much less energy than incandescent or standard fluorescent light bulbs. They come in a range of styles and sizes, and electric utilities often provide instant or mail-in rebates for CFL purchases.
Concentrating solar power (CSP): Concentrating solar power plants collect the sun’s energy through different mirror configurations, converting the high-temperature heat collected into electricity through use of a generator. There are three different types of CSP systems: trough systems, power tower systems, and solar dish/engine systems. Each system uses a different method for collecting solar energy. To learn more about CSP, visit the U.S. Department of Energy’s Concentrating Solar Power website.
Criteria pollutants: These are man-made pollutants such as carbon monoxide, nitrogen oxides, nonmethane volatile organic compounds (NMVOCs), and sulfur dioxide, that have indirect effects on global warming. They are primarily emitted as byproducts of fossil fuel and biomass combustion. Lead and particulates are also criteria pollutants. Although these pollutants only remain in the atmosphere for a short time, the chemical reactions that remove carbon monoxide, NMVOCs, and nitrogen oxides from the atmosphere promote the formation of ozone, which is harmful to people and animals at ground level.