The fugitive elephant in the room

The fugitive elephant in the room

By Mat Hope

But as we've explored before, scientists are struggling to establish the full impact of increased shale gas production on the climate, due to methane that escapes during the extraction process – known as fugitive methane emissions.

The graph on the left, taken from a paper by Robert Howarth, appears to show natural gas electricity generation emissions – the towering left bar – can be much higher than coal's.

As you can see from our chart, Howarth's research gives some of the highest estimates of fugitive emissions for the studies using a bottom up approach – hence his contention that gas can be more polluting than coal.

The second graph, from Heath et al, appears to show the opposite – that coal's generation emissions (on the left) are much higher than those from both conventional and shale gas.

The main reason Heath et al don't include fugitive emissions in their graph is because researchers are a long way from agreeing a standard or average leakage rate. So who's right?

Source: Various, see this Google Doc for details. Graph by Carbon Brief. ) means value is for unconventional – i. e. shale – gas wells only, (*) means the value in the graph is the mid-estimate or mean of a range where a 'best estimate' is not given.

In short, it's because Howarth's data includes an estimate of fugitive emissions, while Heath et al's doesn't.

Fugitive emissions are a problem because methane is a potent greenhouse gas – approximately 25 times more powerful than carbon dioxide over a 100 year timescale.

Read more here: Business Spectator

    

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