written 7 January 2024
published 14 January 2024
Natural gas, named originally to distinguish itself from "rock gas" formulated from coal, is mostly methane, CH4. With four hydrogen atoms for each carbon atom, natural gas has the highest hydrogen to carbon ratio of all fossil fuels, and has been billed as a "cleaner" energy source for decades. Globally, natural gas produces 23% of all the electricity and is 24% of all energy sources in total.
Being gas at room temperature and pressure, it is more difficult to store and ship than the other two fossil fuels: crude oil and coal. When the natural gas sources are relatively close to where it is consumed, pipelines are used. The US has over 3 million miles of high-pressure line, operating at as much as 100 times atmospheric pressure.
Over time, age and gas flow erodes the pipes, causing local disasters, such as PG&E's 2010 San Bruno explosion and fire. In 2015, the Southern California Gas underground natural gas storage near Los Angeles blew out, producing the largest methane leak in US history.
Global natural gas consumption is expanding. China, and others, are shifting away from domestic coal and expanding gas imports. The recent invasion of Ukraine resulted in sanctions against Russian natural gas imported into the EU, further stimulating overseas natural gas shipping. Increasing demand raises prices. A few years ago, PG&E announced that they will no longer expand their domestic natural gas system, in part because global gas prices are fluctuating too much.
To make overseas shipping possible, the gas is liquified. Liquified natural gas (LNG) is cooled to -163°C, taking only 1/600 of the volume, but requiring about 10% more energy to cool it, and further energy to reformulate back to gas at the consumer end. LNG facilities only make financial sense if they operate for 30 years.
The climate crisis comes from increased atmospheric heating, resulting from changing chemistry in the atmosphere. Because some chemicals, such as carbon dioxide, are relatively transparent to light, but absorb heat radiated back from the surface of the Earth, they are called greenhouse gases (GHG). As with all fossil fuels, natural gas combustion produces carbon dioxide as a by-product. Because this carbon was sequestered millions of years ago, it adds to the current atmospheric carbon dioxide problem.
Natural gas is even worse as a greenhouse gas than just the carbon dioxide addition, because methane is over 80 time more potent a GHG than carbon dioxide. Even though methane breaks down in the atmosphere within a decade, becoming carbon dioxide, it has massive short-term impact. With the climate crisis entering into an explosive expansion phase, this becomes increasingly problematic.
All natural gas systems leak methane into the atmosphere. Since it is colorless and odorless (the smell of natural gas is added), leaks throughout the industry are numerous and generally unnoticed. As LNG is shipped, some heats back to gas and is vented to the air.
The global economy adds 38 billion tons of CO2 each year, and 135 million tons of methane, of which 15% comes from natural gas production. The heating impact from methane is equal to another 11 billion tons of CO2 each year.
Beginning in 2005, US production of natural gas leaped. As conventional oil depleted and production began to taper off, producers were forced to expand into more expensive unconventional oil resources, mostly deep ocean and fracking, to meet global demand. Fracked wells now account for 1/2 of the oil and 2/3 of the natural gas produced in the US.
Fracking is a type of tertiary recovery method, required where fossil fuel reserves are thinly located in rock, like marbling in beef. Consequently, fracking is very energy intensive, using high pressure to crack open the rock, injecting sand to keep it open, and then pumping out the thin layer of oil and gas. Because the resources are very dispersed, production from a fracked well begins to deplete rapidly, declining about 50% in just the first year, so new wells have to be drilled continually. This means the cost of oil and gas has to remain high enough to keep production profitable, and the most economical areas are already being depleted.
Natural gas is expensive, and the prices will continue to rise. Combustion adds to the atmospheric CO2problem, and methane leaks are powerfully worse. However, the push is on to move past natural gas, if we want a habitable planet for our descendants.
