Natural gas (methane), we are endlessly told, is a clean fossil fuel. This claim is based on lower carbon dioxide emissions compared to other fossil fuels. Emissions are indeed lower, but natural gas under the best conditions is far from a truly clean source of energy.

Coal is our standard for the dirtiest fossil fuel. Burning coal creates 0.37 kilograms (kg) of carbon dioxide emissions for every kilowatt-hour (kWh) of energy released.

Burning gasoline creates 0.27 kg of carbon dioxide emissions (CO2) per kWh of energy. That’s 73% as much carbon dioxide as coal, for the same energy released.

Diesel fuel is a little “cleaner” than gasoline. It creates 0.24 kg CO2 per kWh; 65% of the emissions of coal.

Methane creates 0.23 kg CO2 per kWh. This is 62% of the emissions of coal, and only a little better than diesel fuel (Methane emissions are 96% of diesel fuel CO2 emissions). If we were going to label methane as “clean,” we should in fairness recognize diesel fuel is a very close second.

In reality, if we had four children we thought were dressed for school, and then discovered one was covered from head to toe in dirt while the other three had managed only to keep their shirts halfway clean, we would not call any of them “clean.” That’s how it is with fossil fuels. None of them are clean, though some are dirtier than others.

Let’s say we start with an extreme case – an economy run entirely on coal. CO2 emissions are too high, so we convert that economy to run entirely on methane. OK, now that we are running on clean fuel, we can grow the economy at a respectable 4% per year. Only 13 years later, our CO2 emissions will be higher than they were when we were running entirely on coal.

The simplest sort of analysis makes it clear that methane from any source is not a long-term solution for excess carbon dioxide emissions. It is better than coal, and a little better than oil-based fuels, but certainly not a solution.

There are considerable variations in the quality and energy content of coal. The figures used above, which are average values for grades of coal and other fuels typically used in the United States, are taken from “The Engineering Toolbox,” freely available at http://www.engineeringtoolbox.com/. The specific table used is located at http://www.engineeringtoolbox.com/co2-emission-fuels-d_1085.html.

Coal, of course, has other problems besides carbon dioxide emissions: soot, mercury, sulfur, destruction of the landscape by mining operations and so on. All the fossil fuels have similar issues. In particular, methane produced by fracking, with or without horizontal drilling, could be worse for our environment than coal mining.

If we imagine that natural gas is “clean,” and if we can be persuaded that environmental damage can be minimized, then we might believe allowing fracking makes sense. Once we know that natural gas has only managed to keep his shirt halfway clean, while his pants are just as filthy as those of his brothers, that argument is much less convincing.

Art Myatt

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