Green Glossary

These are liquid fuels—for example, biodiesel and ethanol—that are derived from biomass (i.e., plant or animal material like corn, wood, vegetable oils, or animal fats). Unlike gasoline or diesel fuel, which are derived from petroleum, pure biofuels are considered renewable sources of energy. Presently, biofuels like biodiesel and ethanol are not typically available in their purest form; instead, they are often mixed with their petroleum-based cousins.
Refers to plant material or animal waste that can be used directly as fuel or converted into biofuels. This can include wood logs for a fire as well as remnants from other sources, such as bark and sawdust from a paper mill or the stalks and leaves that are left over after harvesting ears of corn.
Carbon Footprint
This term is used to describe the total impact a living creature, product, or service has on the environment in terms of the amount of carbon dioxide and other greenhouse gases it produces. Human activities such as heating a house, driving a car, and producing food and goods all emit some amount of carbon dioxide.
Carbon Offset
A carbon offset represents any action taken to lessen the impact of greenhouse gas emissions that have already been released. Because trees help to balance carbon dioxide levels, planting new trees can lead to the creation of offsets. Carbon offsets can also be purchased from companies and nonprofits who sponsor emissions-reducing endeavors. For measuring purposes, one carbon offset represents the reduction of one metric ton of carbon dioxide.
The average course of weather conditions in a large geographic area over a period of years; includes temperatures, wind velocities, and rate of precipitation.
Climate Change
This refers to any major and lasting alteration in the earth’s climate systems (temperature, wind, precipitation levels). Most recently, human activities that produce greenhouse gas emissions from the combustion of fossil fuels (for example, to produce electric power) have caused the climate change referred to as global warming.
Compact Fluorescent Light Bulb (CFL)
An energy-saving bulb that produces light in a different manner from a conventional incandescent bulb. CFLs must be disposed of properly because they contain small amounts of mercury.
Energy Star
A voluntary government program that helps individuals and families make energy-efficient choices and save money on utility bills by certifying that products meet high standards for energy efficiency. Energy Star is run jointly by the US Environmental Protection Agency and the US Department of Energy. For details, visit
Fossil Fuels
Organic substances used as sources of energy, fossil fuels are usually found underground, within the top layer of the earth’s crust, where they developed during earlier geologic periods. They are considered “nonrenewable” sources of energy because they are being depleted far faster than new ones can form. Examples are anthracite coal, methane, and liquid petroleum.
Global Warming
This is the gradual increase in temperature of the earth’s lower atmosphere. This climate change is occurring due to the increase in greenhouse gas emissions during this century.
Greenhouse Effect
This occurs when gases trapped in the earth’s atmosphere cause a change in the temperature of the planet because the gases absorb too much infrared radiation from the sun.
Greenhouse Gases
Substances (mainly carbon dioxide, methane, nitrous oxide, and water vapor) in the earth’s atmosphere that trap heat and help regulate climate at the earth’s surface. While these gases are essential to keeping the earth warm, when their levels increase too rapidly, too much heat is absorbed, and global warming occurs.
Green Roof
A roof that is planted with any kind of vegetation, either entirely or in part.
Hybrid Car
Vehicles that use both a traditional engine (combustion) and a rechargeable system (typically operated by a battery) to improve mileage, cause less pollution, and decrease need for gasoline.
Nonrenewable Energy
Energy (typically from a fossil fuel) that comes from a limited source that cannot be replenished and eventually will be depleted.
The process of making something new out of old materials (one example is returning used plastic bags to the store so that they can be made into new plastic bags, composite lumber, and playground equipment). Recycling requires energy to collect, process, and use the old materials to create new products. Compare with Reuse.
Renewable Energy
Energy produced by natural resources such as water, wind, or the sun or from a source that can be replenished naturally and on a regular basis. Renewable energy sources typically release smaller quantities of greenhouse gases than nonrenewable energy sources.
This occurs when a product does a job more than once or repeatedly with little or no modification. One example is returning to the store with the same plastic bags you used last week to pack the groceries. No extra energy is required in reusing a product. Compare with Recycle.
Source Reduction
This refers to a change in the design of products and packaging to decrease potential waste items before they are created.
This concept allows for the use of resources—and our planet in general—today at a rate that meets the present needs without jeopardizing the ability to accommodate the needs of future generations. Sustainable use can be applied to everything from the way we develop our cities to how we grow our food to how we treat our natural resources.
This term refers to the short-term, variable atmospheric conditions (such as temperature, precipitation levels, and cloud cover) in a prescribed area. Compare with Climate.