The “clean” fossil fuel, natural gas is often mistakenly thought to have very little environmental impact. But newer extraction methods and the sheer quantity of natural gas consumed make it one of the largest greenhouse gas contributors globally.
Oil’s sibling is natural gas. Methane, the primary constituent of natural gas, is formed by the breakdown of organic material. In landfills, the rapid breakdown of organic material in the absence of oxygen creates a mix of gases that includes methane; under the Earth’s crust the breakdown of prehistoric plankton forms both oil and natural gas. To form natural gas, the plankton is simply “cooked” at higher temperatures and pressures for longer periods of time than for oil, breaking the molecules into shorter chains of carbon atoms. But since the pressure and temperature can vary even within one hydrocarbon reservoir, oil and natural gas are often found together.
Global natural gas production equals 3,139 billion cubic meters annually, which is the energetic equivalent of 21 billion barrels of oil per year—roughly two-thirds the energy content of all the oil produced in the world. Global proved reserves of conventional natural gas are distributed widely, with the largest shares belonging to Russia (24 percent), Iran (16 percent), and Qatar (14 percent). The United States is currently the world’s top natural gas producer, followed by Russia.
Natural gas is a highly coveted resource; it can have a high energy density (when pressurized into a liquid form), and it produces fewer greenhouse gas emissions at the burner tip than oil and coal. While natural gas is traded globally, its transport by sea in the form of liquefied natural gas (LNG) requires significant specialized infrastructure, making it more of a regional resource compared to oil. In the United States, natural gas is used prominently in the electricity sector to meet peak demand, as well as in a variety of functions in the industrial and manufacturing sectors. Natural gas also serves as the main heating and cooking fuel for much of the United States and world.
Conventional natural gas has the lowest greenhouse gas emissions per unit of energy of all the fossil fuels, but since it is used in such high quantities it accounts for over 20 percent of U.S. carbon dioxide emissions. Hydraulic fracturing (or “fracking”) is now being used to produce harder-to-access shale gas deposits, and this may increase considerably the greenhouse gases per unit of energy from natural gas. Recent studies suggest that this increase may nullify any potential savings in greenhouse gas emissions from burning natural gas instead of oil or coal. Some climate and energy experts argue, however, that with strong regulation of the industry, including standards on preventing unburned methane leakage systemwide, significant greenhouse gas reductions can be achieved from burning natural gas rather than coal.