The name “natural gas” might be a puzzle. After all, how could there be such a thing as unnatural gas?
The reason we call natural gas what we do has to do with history. There was a day that people made burnable gas by heating coal. The gases that came off the coal were piped around cities, where they did things like light street lamps and even power cook stoves in homes.
Coal gas, as it was known, had its downsides. For one thing, it often contained carbon monoxide. And it took energy to make the gas, so it never could be truly cheap.
Happily, geologists figured out that a gas from within the earth would burn well. Because it came from Mother Nature rather than being manufactured by people, folks called the new energy source “natural gas.” In time, natural gas replaced coal gas.
Natural gas is mostly made up of what a chemist would call methane. Methane is made of a carbon atom bound to four hydrogen atoms.
In recent years a lot more natural gas has come online in our country due to new mining methods, including hydraulic fracturing or “fracking.” Fracking allows the extraction of natural gas and sometimes petroleum from rocks such as shale.
But now there is an even newer development that may add a lot more natural gas to what people can burn each year.
Japanese researchers and engineers have now liberated the main ingredient of natural gas from what are called methane hydrates that lie on the seafloor. At a depth of over 3,000 feet, the Japanese tapped a vast reservoir of natural gas bound up in frozen water under high pressure on the seafloor.
The hydrates are made of methane molecules trapped in ice. Some call the hydrates “ice that burns” or “fire ice” because you can ignite it with a match.
The United States Geological Survey estimates worldwide resources of conventional natural gas are about 13,000 trillion cubic feet. It’s not so easy to estimate what methane hydrates on the seafloor and in permafrost may contain, but the USGS gives this resource the range of 100,000 to almost 300,000,000 TCF. Not all of the gas may be extractable, but clearly the total amount of methane hydrates in the world is immense.
Another way of thinking about the size of the resources that methane hydrates represent is to consider how much carbon is in the ice crystals. The USGS states that the volume of carbon in methane hydrates is estimated to be twice the carbon contained in all types of fossil fuels the world around, including in coal.
Like other energy resources, there are serious questions about environmental tradeoffs involved in using a lot of methane hydrates to meet our energy needs.
Methane that escapes from mining into the air is a powerful greenhouse gas, much more significant per molecule than carbon dioxide. And methane that’s corralled by us into pipelines and burned inexorably creates carbon dioxide, although in smaller quantities per unit of heat than what happens when we burn coal.
Still, the large estimates of how much methane hydrates are available may mean the period of time we rely on fossil fuels for many of our energy needs will be considerably extended — and that has implications for our climate concerns.
One thing, I think, is certain: we’ll be hearing much more about the ice that burns in the future.
E. Kirsten Peters, Ph.D., a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.