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Carbon Brief Staff

Carbon Brief Staff

09.09.2013 | 1:30pm
ScienceClimate change is biggest shale gas risk, scientists say
SCIENCE | September 9. 2013. 13:30
Climate change is biggest shale gas risk, scientists say

A UK shale gas boom would leave UK carbon emissions pretty much unchanged, and could cause global emissions to increase, a new government report suggests.

The new research by the Department of Energy and Climate Change’s (DECC) chief scientific advisor, David Mackay, will make difficult reading for the government which publicly supports shale gas development but also has a legally binding obligation to reduce the UK’s emissions.

The report suggests it’s time to move on from discussing shale gas in terms of earthquakes and Sussex villages and focus on the climate change impact of shale gas.

Mackay’s team looked at potential “lifecycle” carbon emissions from shale gas, which include drilling, extracting and burning the gas.

The results suggest shale gas emissions are similar to other types of natural gas.

gas emissions

DECC estimates greenhouse gas emissions for each kilowatt hour of electricity generated using shale gas at between 423 and 535 grams of carbon dioxide equivalent. That’s significantly less than generating electricity using coal – which produces emissions in the range of 837 to 1130 grams.

While domestic shale gas may have lower emissions than imports of gas from outside of Europe, it would probably have higher emissions than “conventional gas”, much of which comes from the north sea or through pipelines from Norway and Holland.

In other words, whether shale gas is good or bad for UK emissions would depend on what kind of gas it replaced.

Mackay said “it is credible” that domestic shale gas could replace tanker imports of liquid natural gas (LNG), much of which comes from Qatar. In that case, the lifecycle emissions are similar enough that this wouldn’t help the UK reduce emissions overall.

On the other hand, if LNG imports continue and domestic shale gas replaced “conventional gas”, much of which comes from the north sea or through pipelines from Norway and Holland, overall gas generation emissions could rise.

But once you start thinking globally, more shale gas use could mean there’s more coal for other countries. The US shale boom has meant the UK has been taking advantage of cheap surplus coal in recent years. And that could mean UK shale gas production actually causes a global emission increase, Mackay says.

How fracking happens affects emissions

Shale gas will only have lower emissions if extraction is done carefully, the report warns.

Once fracking is completed, some of the chemical mix used to fracture rock and release gas flows back to the surface, along with some of the fracked gas and methane, known as fugitive emissions.

As methane is a more potent greenhouse gas than carbon dioxide, how this mixture is dealt with affects how emissions intensive the whole process is.

The gases can simply be vented into the atmosphere. Or they can be burnt off, in a dramatic process known as flaring. But the UK’s Office of Unconventional Oil and Gas requires both processes to be kept to the “minimum that is technically possible”, so Mackay’s team don’t envisage this happening very often.

It’s more likely that companies will attempt to trap the gases so they can be sold or used to power onsite equipment. If that happens then shale gas emissions will be towards the lower end of Mackay’s estimates.

As such, the report says the government should focus on forcing companies to capture fugitive emissions at each stage of the process to make sure shale gas emissions are as low as possible.

Climate change, not earthquakes

The experts presenting the report said the recent swathes of shale gas media coverage have encouraged the public to worry about the wrong things.

Professor Mike Stephenson from the British Geological Survey said experts had “a really good handle of what’s going on” when it came to fracking and some of its allegedly scarier impacts, such as earthquakes.

Professor of Geological Engineering at the University of Strathclyde, Zoe Shipton, said these were problematic distractions when shale gas’ “biggest risk is climate change”.

As the report shows that shale gas will be at least as carbon polluting as conventional gas, the wider question remains one of how the UK will reduce emissions.

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