How Bad is the Aliso Canyon (Porter Ranch) Gas Leak?

A huge underground natural-gas storage field located under the northern San Fernando Valley in Los Angeles has sprung a leak. The California Air Resources Board estimates that the Aliso Canyon leak is releasing about 30,000 kilograms of methane per hour. Los Angeles County Supervisor Michael Antonovich characterized the leak as a “mini Chernobyl.” Erin Brockovich called it the “BP spill on land.”

Methane has about 60 times the global-warming effect of CO2, but it persists a much shorter time than CO2 in the atmosphere – only about 12 years. The EPA, combining these factors, concludes that a pound of methane in the atmosphere has between 28 and 36 times more global warming potential (GWP) than a pound of CO2.

We should be using the higher numbers, 60X and more, in formulating policy. We will eventually reduce GHG emissions to a sustainable level, i.e. the level at which natural processes remove GHGs from the atmosphere at the same rate we emit them. Atmospheric GHG concentrations will continue to increase until we arrive at that point. To reduce the worst effects of global warming, we need to get to the equilibrium point as quickly as possible, so that the peak GHG concentration is as low as possible.

The largest component of our long-term solution to climate change will be the elimination of fossil fuels as energy sources. We will have to stop burning coal, oil, and natural gas, in electric power plants and our homes. In the next decade or two we will have to dismantle our natural-gas distribution infrastructure. This means Southern California Gas Co. will stop using the underground reservoir in which it stores natural gas for Los Angeles, the source of the Aliso Canyon leak.

Re-tooling our energy system is a huge, long-term project. In the meantime, we continue burning fossil fuels, increasing GHG concentrations, increasing the planet’s temperature. We can help minimize the peak long-term GHG concentration by focusing now on short-term GHGs while the longer-term project is being undertaken. As Yale University’s Climate Institute sums it up, “with the world already flirting dangerously with the two degree warming threshold, mitigation of short-lived greenhouse gases offers one of the only opportunities to actually reduce radiative forcing in the near term, so ‘buying time’ to control and begin reducing emissions of long-lived greenhouse gases.”

In this context, the Aliso Canyon mega-leak is an environmental disaster. 30,000 kilograms (30 metric tons or MT) of methane per hour is 262,800 metric tons per year, or 15.8 million MT/year of CO2 equivalent (CO2E), using the 60X methane/CO2 conversion factor. The average car emits 4.7 MT of CO2E/year, so the GHG effects of the leak are equivalent to 3.4 million cars. Another way to appreciate the leak’s huge scale is by comparing it to emissions from coal-fired power plants, which average 1.21 pounds of CO2 per kWh of generated energy. The leak’s GHG emissions are the equivalent of the GHG emissions from coal-fired power plants generating 25 Gigawatts of electricity, which is pretty close to California’s total electric-power usage. Any way you look at it, the Aliso Canyon leak is an environmental disaster, significant on the national scale.

After getting the Aliso Canyon leak under control, we need to examine what potential there is for other large methane leaks, and make sure we have better means of controlling them, should they occur. The gas company detected the Aliso Canyon leak on Oct. 23, 2015, and estimates that it may take until March 2016 for the leak to be plugged. This five-month delay in staunching the leak is unacceptable. We also need to better control smaller methane emissions that occur every day from leaking pipelines, oil fields, waste dumps, and other sources. Reducing emissions of methane and other short-term GHGs is one of the most cost-effective measures we can take to combat climate change. Let’s make sure we do all we can to eliminate methane emissions.