The primary ingredient in natural gas is methane. There are three types of methane:
- Thermogenic methane: This methane is created when sediment and mud pressurize the putrefied remains of plants and animals over millions of years. This happens at high temperatures — hotter than it takes to make oil — and it takes place 1 to 2 miles (1.6 to 3.2 kilometers) beneath the surface of the Earth.
- Abiogenic methane: Over the course of millions of years, hydrogen-rich gases and carbon molecules rise to the surface. They combine into the proper molecular proportion to create abiogenic methane (one carbon atom to four hydrogen atoms), which then settles into large, subterranean deposits.
- Biogenic methane: Microorganisms called methanogens feed on decaying organic matter. What goes in must come out, and the fecal matter excreted by the methanogens is methane. Methanogens live wherever there is organic material to eat. That includes landfills and the intestines of cows.