Which Natural Gas Liquid is That?

A natural gas plant, at work in the Middle East. (image: Suncor Energy via flickr.com)

From Texas to West Virginia to the New York Stock Exchange, the term “natural gas liquids” has been popping up in recent headlines. These NGLs, which include propane, are a family of chemically-related organic gases, and are part of the haul from the country’s gasfields — or more precisely, the “wet” fields. And what links the NGLs together? They are all hydrocarbons, made up of hydrogen and carbon atoms. (Think: hydrogen + carbon = hydrocarbon.)

That said, they differ in their exact ratio of the two elements, which affects their chemical and physical properties. And the impact of changing the ratio of hydrogen to carbon can be profound. For example, coal and oil have essentially the same elemental make-up as natural gas and propane, just different combinations of the two molecules. But the differences between propane and oil is a story for another blog post. Today, we’re looking at five basic NGLs that typically come from the gas fields, and are later distilled out at a processing plant.

Methane

Methane is the smallest and simplest of this gaseous family, with one carbon surrounded by four hydrogens (CH4). It is the main component of natural gas, and is a key energy source. Unburned, it is a powerful greenhouse gas, over 20 times as strong as CO2 when it comes to trapping heat. As you may have heard, it is a by-product of digestion — especially cow digestion — as well as being found below the earth. So yes, cow flatulence contributes to global warming.

Ethane

Ethane is the simplest hydrocarbon with more than one carbon; its formula is C2H6, or 2 carbons to 6 hydrogens. It is used mostly as an ingredient for making other materials, like plastic, and not for fuel.

Propane

Our favorite, propane, is C3H8 — 3 carbons to 8 hydrogens — and can call itself a common and flexible fuel. Easy to transport and store, as well as clean-burning and non-toxic (though you can’t actually breathe it any more than you can breathe water), this gas is used for cooking, home heating, hot water, appliances, generating electricity, and running vehicles ranging from small forklifts to school buses.

Butane

Getting to more complex molecules, butane’s formula is CH3CH2CH2CH3, or 4 carbons and 10 hydrogens in a chain. Butane is used for cooking, for cigarette lighters, as a propellant in some aerosol sprays, and also as a component in making other chemicals and substances. Unlike propane, butane is toxic, and so less safe to use.

Pentane

As any fan of werewolf movies knows, “pent” means five. (The pentagram that provides protection from werewolves is a five-pointed star.) Pentane has 5 carbons and 12 hyrdogens. It is used primarily as a chemical building block or ingredient — it is used to make certain foams as well as refrigerant — and not primarily as a fuel.