Shale gas is mostly methane. Upon extraction, it is compressed, piped and then burned to produce energy, which releases CO2 into the environment. CO2 and methane are both greenhouse gases, but CO2 is less harmful when released into the environment. According to the US Environmental Protection Agency “Pound for pound, the comparative impact of methane on climate change is over 20 times greater than CO2 over a 100-year period.”1 Incidentally, burning gas for energy produces about half as much CO2 as burning coal.
To ensure the effect of methane on the environment is minimised, it is very important that as much of the gas extracted as possible is used and that as little methane as possible escapes into the atmosphere. The Government’s Department of Energy and Climate Change (DECC) insists that operators must minimise the release of gas into the atmosphere and, when gas can’t be economically used, it must be captured and “flared” to reduce its global warming emissions.2 Flaring, which is the controlled burning of gas, reduces emissions by up to 80% compared to venting, which is only used when absolutely necessary for safety reasons. It is also important to bear in mind that operators will have a commercial incentive not to flare gas, as the gas could otherwise be sold.
The shale gas industry in the UK is also developing “green completion” based on industry best practice, to reduce the emissions of gases into the air, and this is emphasised in UKOOG’s “UK Onshore Shale Gas Well Guidelines”3. This involves using specialist equipment to collect and separate the initial flow of water, sand and gas, so the gas can be prevented from escaping. According to Professor David MacKay, (DECC’s Chief Scientific Advisor), and Dr Timothy Stone (the Senior Advisor to the Secretary of State), “green completions” should be adopted at all stages following exploration.4 According to the Government’s Department of Energy and Climate Change “Green completions and flaring can reduce methane emissions by as much as 95% versus venting straight into the atmosphere.”5
With regards to public health, methane is a naturally occurring gas which we are often exposed to when breathing. However, if breathed-in in large quantities – from a faulty gas appliance in the home, for example – it can displace oxygen in the lungs, causing suffocation. Public Health England (part of the Department of Health) has completed a comprehensive review of the potential health impact of shale gas extraction. The review found that the potential risks to public health from exposure to the emissions associated with shale gas extraction will be low if the operations are properly run and regulated.6
3 UKOOG, UK Onshore Shale Gas Well Guidelines http://www.ukoog.org.uk/images/ukoog/pdfs/ShaleGasWellGuidelines.pdf