Most greenhouse gases are released when stuff burns or rots. The rest are chemicals that accidentally escape.
Whenever something rots or burns it releases varying quantities of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The majority of human greenhouse gas emissions come from burning fuels like oil, coal, or wood. Some also come from the decomposition of trash in landfills, grain in cows’ stomachs, and sewage in wastewater systems. Deforestation, especially in the tropics, is a third major source of emissions—not only does it prevent forests from absorbing carbon as they grow, it releases carbon that was stored in the soil, and if the trees are burned it releases all the carbon stored in their wood.
Some of the chemicals we use are themselves greenhouse gases. These tend to be released in relatively small quantities, but can be extremely potent – some have global warming potentials thousands of times greater than carbon dioxide. The most common are fluorocarbons, which gradually leak from the air conditioning systems in our houses and cars. Other potent greenhouse gases are used as pesticides, electrical insulators, fire retardants, and in various other industrial applications.
We split your personal emissions into four categories based on the activities that cause them: shelter, transportation, consumables, and government.