Natural Gas: From Ancient Fires to the Fuel of the Modern Age

Natural gas is a fossil fuel composed primarily of methane (typically eighty to ninety-five percent), with smaller proportions of ethane, propane, butane, and other hydrocarbons, as well as non-hydrocarbon gases including nitrogen, carbon dioxide, and sometimes hydrogen sulfide. It is formed by the same geological processes that create oil — the accumulation and burial of organic matter over millions of years, followed by transformation under heat and pressure — and is found both in association with oil deposits (associated gas) and in reservoirs containing little or no oil (non-associated gas or dry gas).

Natural gas is the fastest-growing major energy source in the world and has become the preferred fuel for electricity generation in many markets, displacing coal on economic and efficiency grounds. It is the dominant residential fuel for heating and cooking in most of the developed world, the primary industrial feedstock for nitrogen fertilizer production, and the fuel of choice for the most efficient combined-cycle power stations. Its combination of high energy content, clean combustion (producing significantly less carbon dioxide, sulfur dioxide, and particulate matter than coal or oil per unit of energy), ease of distribution through pipelines, and competitive cost has driven its rise to become the second or third largest energy source in the global primary energy mix.

The geopolitics of natural gas differ importantly from those of oil. Because natural gas is more expensive to transport than oil — it is less energy-dense than oil by volume, and either requires compression into pipelines or liquefaction and specialized tankers (LNG, or liquefied natural gas, ships) for transportation — natural gas markets were historically regional rather than global. European countries depended on gas from nearby deposits in the North Sea or from pipeline imports from Russia; Asian countries depended on LNG imports from Indonesia, Malaysia, Australia, and the Middle East. The United States was essentially self-sufficient in natural gas for most of the twentieth century. Only with the shale revolution and the expansion of LNG trade has natural gas become a more genuinely global commodity, with prices in different regions becoming more correlated.

The history of natural gas as a commercial energy source is substantially shorter than that of coal or oil — commercial natural gas production did not begin until the mid-nineteenth century — but its use in certain applications (eternal fires, gas seeps, early gas wells) extends back thousands of years.

Ancient Encounters with Natural Gas

Natural gas seeps to the surface in many parts of the world where subsurface gas deposits are under pressure and can find pathways through rock fractures. These seeps have been observed and, in some cases, deliberately exploited since ancient times.

The most culturally significant natural gas seeps in history were those in the ancient Near East that gave rise to the "eternal fires" of Zoroastrian religion. The Zoroastrian eternal fire at Baku on the western shore of the Caspian Sea — at the site now occupied by the Ateshgah Fire Temple — burned continuously for centuries, fed by natural gas venting from shallow deposits. The temple was a place of pilgrimage for Zoroastrian priests from Persia and Hindu pilgrims from India who came to worship the sacred eternal flame. The Baku eternal fire was still burning when Russian engineers arrived in the nineteenth century to begin commercial oil and gas extraction.