Slow-motion methane disaster

Aliso Canyon has leaked more greenhouse gases in two months than a coal mine does in a year.


In the hills above suburban Los Angeles, a man-made natural disaster of sorts has been unfolding for nearly two months. One can't see it or hear it, and it's not leaving a trail of dead animals and plants in its wake. It's potentially catastrophic, nonetheless.

On October 23, workers at the massive Aliso Canyon subterranean natural gas storage facility north of the L.A. suburb of Porter Ranch noticed that one of their old wells was leaking. When the usual fixes didn't take, the workers surmised that the leak must be originating far underground, near the natural gas reservoir, itself. And fixing that would be a long, drawn out challenge.

Two months has gone by, and the leak is still leaking. Big time.

Not long after the disaster began, residents of Porter Ranch were able to smell the rotten-egg odor of the mercaptons, which are added to natural gas in order to make it detectable. The additives caused some folks to suffer from burning eyes, nausea, headaches and other health issues, forcing dozens to leave their homes.

The long-term impacts might be even more serious. Natural gas is mostly made up of methane, which is about 87 times more potent in terms of global warming than carbon dioxide over a 20 year period. Because methane breaks down in the atmosphere over time, the potency drops to about 34 times that of carbon dioxide over a 100 year span (the EPA sticks with 25 times the warming potential over 100 years, an outdated figure).

And since it began, the leak has been emitting methane at a rate ranging from 36,000 to 58,000 kilograms per hour, according to the California Air Resources Board. That adds up to a total of some 62,000 metric tons of methane emitted as of Dec. 16  about four times what had been lost nationwide in natural gas transmission pipeline "incidents" all year. And the number keeps growing.

With just two months of emissions under its belt, the Aliso Canyon facility has already leaked enough methane to put it in the number two spot in the West for the entirety of 2014. Measurements for the San Juan Basin Geologic seeps only include the portion of the Basin in Colorado on non-Ute land.
Graph: Jonathan Thompson. Data: California Air Resources Board, EPA, LT Environmental.

Natural gas burns far more cleanly than coal, emitting about half the carbon dioxide per unit of energy generated, making it a climate-friendly replacement for coal. Leaks like this one, however, undermine the advantages of natural gas. Various studies show that when as little as 3 to 4 percent of the total natural gas produced is lost to leakage, it becomes worse for the climate than coal.

For some perspective, consider the emissions thus far from the leak:

  • 1,128: Metric tons of methane emitted from the Aliso Canyon leak per day.
  • 775: Number of households that amount of natural gas could heat for an entire year.
  • 62,000: Metric tons of methane emitted from leak as of Dec. 16, 2015.
  • 2.1 million: Metric tons of carbon dioxide equivalent (assuming a 100-year impact) emitted from leak as of Dec. 16, 2015.
  • 2.8 million: Metric tons of carbon dioxide emitted by the Navajo Generating Station in Page, Arizona, over the same period of time.

It could be months before a final fix is found for the Aliso Canyon leak. And as long as it keeps spewing, it will continue to raise questions as to how "clean" natural gas really is.

UPDATE: The graph was updated on 12/29/2015 to reflect new emissions data for the Aliso Canyon leak and to correct an error in the data for the San Juan Basin geological seeps.

Jonathan Thompson is a senior editor of High Country News. Homepage photograph of Aliso Canyon leak courtesy Environmental Defense Fund. 

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