What is a Carbon Footprint?
“Carbon footprint” is another term for greenhouse gas inventory. Greenhouse gas inventory is the total amount of greenhouse gases produced to support human activities. It is the sum of all greenhouse gas emissions which were created as a result of an entity’s activities during a given time frame. The principal greenhouse gases that enter the atmosphere because of human activities are:
Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle.
Methane (CH4): Methane is 20 times more effective in trapping heat in the atmosphere than carbon dioxide (CO2). Methane is emitted via a number of natural sources and human activities, for example: the production and transport of coal, natural gas, and oil, livestock and other agricultural practices, and by the decay of organic waste in municipal solid waste landfills.
Nitrous Oxide (N):Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes.
Fluorinated gases: Fluorinated gases are sometimes used as substitutes for ozone-depleting substance(i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”). (Source: Environmental Protection Agency, Greenhouse Gas Emissions website)
When reporting a carbon footprint, the above-listed greenhouse gases are reported as metric tonnes of "carbon dioxide". The Greenhouse gases are converted using a conversion factor called a Global Warming Potential (GWP). A GWP is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming.