Fugitive shale gas emissions can be kept low, says new study, at a cost
Shale gas supporters see it as the key to a clean energy future, while critics claim the production process makes it dirtier than coal.
So fracking fans – among them the Prime Minister and Mayor of London – will be pleased with the results of a new US study which suggests the amount of greenhouse gases which escape during shale gas production are lower than previously thought.
Well completion
Gas is lower-carbon than other fossil fuels like coal. But the key climate issue with shale gas is how much of the gas escapes into the atmosphere when wells are drilled and operated.
Sand and liquids used in the drilling process have to be cleaned out before gas extraction can begi. This is called “well completion”, and methane – a more potent greenhouse gas than carbon dioxide – can escape into the atmosphere.
These methane emissions are known as fugitive emissions and they can make shale gas considerably worse in climate terms than it first seems.
One well known estimate suggests shale gas production can even be more emissions intensive than coal. (The study sits at one end of the spectrum of expert opition.)
A new paper published in the Proceedings of the National Academy of Sciences yesterday suggests fugitive emissions are far lower than this, however.
The study measured fugitive emissions from 190 gas production sites. It finds well completion emissions are lower than earlier studies suggest. Once leaks from drilling equipment and around the production sites are taken into account, the estimate rises to about the same level as the US government’s official estimate.
Lock them up or set them free
Fugitive emissions depend on how much care is taken in extracting shale gas, the study confirms.
The way companies deal with escaping gas significantly affects how much shale gas production contributes to climate change. A Department of Energy and Climate Change (DECC) report released last week estimated that well completion could account for up to 80 per cent of fracking emissions.
Fugitive emissions can be captured and put back into the gas system, a technique called reduced emissions completion (REC). They can be released into the atmosphere (‘venting’), or burnt off (known as flaring).
This graph shows the emissions for shale gas produced using each process, alongside lifecycle emissions from importing gas in tankers for comparison.
DECC says that venting, the highest emitting process, will not be permitted in the UK – that’s why it’s in grey.
Flaring emissions are only slightly higher than REC emissions, as the graph shows. While this could be an option, local communities are likely to be concerned about flaring, which is basically burning the gas off in fiery jets.
That leaves REC looking like the most likely option. The only company to currently be actively drilling for shale gas in the UK, Cuadrilla, told DECC it aims to pursue this approach, capturing all fugitive emissions and putting them back into the gas system.
Normally, REC captures around 90 per cent of fugitive emissions. But while REC is the most environmentally friendly way to deal with fugitive emissions, the equipment to do it can be expensive. Venting or flaring is cheaper.
So while only allowing REC could make shale gas a more environmentally friendly option, it might means it will be more expensive.
Fugitive emissions policy
The new study implies that keeping fracking emissions low is an issue for policymakers as much as it is for engineers.
It suggests shale gas production can be less emissions-intensive than some previous estimates, but only if well completion is done in an environmentally friendly way.
It also highlights the need to develop less leaky equipment and ensure the methane doesn’t escape elsewhere on the production sites.
The government needs to bear all of this in mind as it considers the role of shale gas in securing the UK’s energy future while keeping to its legally binding climate change commitments.