A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Methane produced in BioStar facilities replaces methane derived from fossil fuels. The carbon in the biodegradable waste is part of a carbon cycle and, as such, the carbon released from the combustion of biogas can be thought of as having been removed by plants in the recent past, for instance within the last decade, but typically within the last growing season. If these plants are re-grown, as is the case with crops, it can be argued that the systems can be considered to be carbon neutral. This contrasts with carbon in fossil fuels that have been sequestered in the earth for many thousands of years.