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What are greenhouse gas emissions?

Greenhouse gasses are gasses that trap heat in the atmosphere much as a layer of glass or translucent plastic traps heat in a greenhouse used for growing plants.  The term greenhouse gas emissions typically refers to gasses that are released from anthropogenic (human-influenced) sources, such as the burning of fossil fuels.

What are the most common greenhouse gasses?

To understand how to reduce greenhouse gasses, we must first understand what they are and how they enter the atmosphere. 

Most Common Greenhouse Gasses

Carbon dioxide (CO2)

Carbon dioxide is emitted from the burning of fossil fuels for transportation, heating, energy generation, etc.

Methane (CH4)

Methane is not as abundant as CO2 in the atmosphere but, with a global warming potential approximately 30 times higher than that of CO2, it is much more potent. Some methane is naturally released by decaying vegetation and by the bacteria in wetlands and swamps. But since 1750, the amount in the earth’s atmosphere has doubled due to human activity, primarily due to the oil and gas industry, agriculture, and landfills.

Here’s how methane emissions occur:

OIL AND GAS INDUSTRY The fossil fuel industry generates a third of all methane emissions. The gas leaks from pumps, pipelines and wells as oil and natural gas are extracted and transported. There is also growing evidence that the decomposition of petroleum-based plastic discarded in landfills and in oceans is responsible for methane emissions. 

AGRICULTURE (especially livestock) As they digest their food, farm animals release methane (primarily in the form of burps, but also flatulence and manure).  According to the United Nations’ Food and Agriculture Organization, livestock — including cows, pigs, sheep and other animals — are responsible for about 14.5%of global greenhouse gas emissions, with cows the primary offenders.  There are currently an estimated 1.3 to 1.5 billion cows on the planet, and each animal releases an average of 30 to 50 gallons of methane gas per day.

LANDFILLS Methane is emitted from landfills as organic matter such as food waste, wood and paper decompose.

Nitrous oxide (N2O)

Nitrous oxide is emitted from agricultural practices (primarily chemical fertilizer use), the combustion of fossil fuels, solid waste, wastewater treatment systems and other industrial activities.

Fluorinated gasses (F-gasses)

The gasses in this category (including Hydrofluorocarbons - HFCs, Perfluorocarbons - PFCs,  Sulphur hexafluoride, or SF6, and others) are emitted from technological innovations such as refrigeration systems, LCD (Liquid Crystal Display) panels, certain types of solar panels, chemical lasers and electrical transmission systems during their lifetime, and also from industrial processes such as semiconductor manufacturing, aluminum production and magnesium production.

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The Maine Climate Science Portal was envisioned and developed by Maine Climate Action Now. Content development, to date, has been a largely-volunteer effort. Click here to see a full list of contributors.

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