Natural Gas is often a blend of the lightest alkanes, hydrocarbons of the CnH2n+2 series, as it emerges from a production steel pipe. Most of the contaminants are removed during gas processing before the finished product, which is 95 percent methane, reaches customers. Natural Gas is abundant, inexpensive, easy to transport, and has minimal emissions and high combustion efficiency.
Natural Gas-fired heating furnaces have maximum efficiencies of 95 to 97 percent, and combined-cycle gas turbines now have overall efficiencies of little more than 60%. Although burning gas produces carbon dioxide, the energy-to-carbon ratio is excellent. Burning a gigajoule of Natural Gas creates 56 kilograms of carbon dioxide, which is about 40% less than bituminous coal’s 95 kilograms.
So far, everything has been green. However, methane is a potent greenhouse gas in its own right, with 84 to 87 times the global warming potential of carbon dioxide when measured over 20 years (and 28 to 36 times as much over 100 years). And some of it makes its way out. According to a 2018 assessment of the United States’ oil and Natural Gas supply chain, emissions were nearly 60% greater than the Environmental Protection Agency had projected.