Behind the Grid: Natural Gas (Methane)

Natural Gas (Methane)

(Published, 05/01/2020, Ruralite)

Natural Gas Refinery
Natural gas tanks in the Refinery industry

More electricity is generated by natural gas than any other energy resource in the United States. For over 100 years, coal had been the top source. Is natural gas an ideal solution or just a short-term fit?

What is natural gas?
Natural gas is a fossil fuel formed from decomposed plant and animal matter. The primary ingredient is methane gas (CH4) with several other trace gases and impurities that must be processed, removed, and used separately. Byproducts of natural gas refining include propane and butane gas. Natural gas is mined via underground petroleum wells, gas wells, or through hydraulic fracturing (fracking).

How is it used to generate electricity?
Generating electricity is the process of converting one form of energy to another. In the case of natural gas, it is burned in a turbine which causes a generator to spin. Modern (combined-cycle) turbines are then able to capture the hot exhaust from the turbine to boil water and that high-pressure steam is then used to spin the turbines of electric generators. This means the fuel was essentially used twice, resulting in a highly efficient use of its energy.

What are the challenges and problems with natural gas?
First, natural gas is a finite resource. Like all fossil fuels, it must be mined from the earth and those sources will eventually be depleted. Estimates on when that happens vary greatly from 50 years to 250 years. New finds, new extraction methods and fluctuations in demand heavily impact those estimates.

Extracting natural gas through drilling or fracking directly impacts water, land, and air quality. The US Geological Survey connects fracking to earthquakes but other government organizations do not recognize this claim. Mining and burning natural gas produces pollutants and greenhouse gases including CO2 exhaust, escaped methane, and several others.

Considering the drawbacks, why has natural gas grown to be the top source for generating electricity?
Methane (the main component of natual gas) is among the most energy dense fuels on earth. Burning it releases massive amounts of heat. It is also lighter and easier to transport than coal or petroleum. Among fossil fuels, natural gas is the cleanest. It produces 40% less CO2 than coal. Coal also creates a lot of ash and natural gas does not. It is also very versatile and once it is processed, it can be used at an electrical generation plant or used directly to heat homes, as vehicle fuel or in various industrial applications.

The United States produces more natural gas than any other nation. 90% of domestic consumption is produced here and the US is also a major exporter. That makes it easier and more cost-stable for electric generating stations to depend on a fuel that is not connected to any foreign entities.

Of all natural gas processed in the United States, approximately 35% is used to generate electricity and 65% is used as “end-use” fuel. Meaning, people burn it to heat their homes, desalinate water, or power machinery.

Energy Density of Fossil Fuels:

  • Natural Gas — 54
  • Propane — 50
  • Gasoline — 46
  • Diesel — 45
  • Crude Oil — 42
  • Coal — 26

Values listed in MJ/kg