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Largest methane leak in US history

Aliso Canyon natural gas storage site, California Aliso Canyon natural gas storage site, California Scott L
25 Feb
The recent gas well blowout in California has been confirmed as the largest methane leak in US history, equivalent to the effect of annual greenhouse gas emissions from over half a million cars

While it may have not raised a fraction of the coverage devoted to the 2010 Deepwater Horizon disaster, there were disturbing reminders of the Gulf of Mexico’s environmental catastrophe in the story of the blowout at the Aliso Canyon natural gas well in California, which led to the evacuation of more than 11,000 local residents and the declaration of a state of emergency.

For 112 days – from 23 October 2015 through to 11 February 2016 – a leak in well ‘SS-25’ spewed out more than 100,000 tons of methane – a greenhouse gas 25 times more potent a greenhouse gas than carbon dioxide.

‘The methane releases were extraordinarily high, the highest we’ve seen,’ confirms Donald Blake, atmospheric chemist at the University of California-Irvine. He also drew attention to the potentially dangerous quantities of compounds found in natural gas, such as benzene, toluene and xylenes, which were measured at ‘above-normal levels’ in surface air samples taken near homes in the nearby Porter Ranch residential area. ‘Some of the volatile organic compounds have been linked to health effects if exposure is long-term.’

Blake is one of a number of co-authors of a new report in the journal Science, which noted that ‘the disaster will substantially affect California’s ability to meet greenhouse gas emission targets for the year’. They found that at its peak the blowout doubled the rate of methane emissions from the entire Los Angeles Basin, and overall was equivalent to the annual greenhouse gas emissions of over half a million cars. ‘This was just a huge event,’ concludes Stephen Conley, from the University of California-Davis, and co-lead scientist on the report.

AlisoCanyonLocLocation of Aliso Canyon Oil Field in Southern California (Image: Antandrus)

Attention is now being directed towards what lessons can be learnt with regards to the infrastructure used in in the US natural gas industry. ‘Our results show how failures of natural gas infrastructure can significantly impact greenhouse gas control efforts,’ said Tom Ryerson, research chemist at the National Oceanic and Atmospheric Administration (NOAA) and also co-lead scientist on the study.

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