A new US study has highlighted how the volume of Los Angeles methane emissions being released is over twice the amount previously thought.

As with carbon dioxide (CO2), methane is a greenhouse gas, but a significantly stronger one produced as a result of activities including farming.  On this basis, the majority of methane assessments have focused on country emissions, negating the big cities and effectively making presumed calculations when needed.

Urban Methane

The new urban methane study was carried out by researchers based at the California Institute of Technology, headed by Debra Wunch.  She and her team took measurements of the greenhouse gases present over LA in the so-called ‘south coast air basin’ – a persistent smog suspended over the city and the circa-15 million people that live there.

Previous research intimated that Los Angeles’ overall annual methane emissions output should be around the 260,000 tons mark, based on its population. However, according to the new study – evidence for which was gathered between August 2007 and June the following year – the actual level was more than double this, at closer to 600,000 tons.

LA Methane Emissions

A large proportion of the electricity used in Los Angeles is created as a result of natural gas incineration- a process that produces heavy amounts of methane.  In 2006, over 10 million tons of this natural gas was transported into Los Angeles and the presence of this – along with the idea of three per cent of it entering the atmosphere – could explain the vast gulf between historical LA methane emissions measurements and the new one.  

“If it's coming from a few potent leaks, one could hope to put a plug in it”, study co-author, the California Institute of Technology’s Paul Wennberg, stressed, adding: “This stuff is valuable.  If you can get enough of it, you want to burn it.”

The additional methane may also be being caused as a result of vehicle emissions, from landfills or from waste treatment centres, the report suggested.

Global Methane Output

Total global methane output is in the region of 582 million tons per annum, from both natural processes and human activities alike.  And - said the report – if other large cities are mirroring LA’s situation, urban methane emissions could be responsible for up to 15 per cent of the overall total.

“The hope is that the processes operating in California may be happening in other cities around the world”, the University of California’s Amy Townsend-Small stated, adding: “If so, this model will be applicable in cities around the world.”

Precise methane emission calculations are, therefore, a compulsion, the report concluded.

See also:

City CO2 Emissions Per Capita