The heavy price of shale gas
Since 2009, the quantity of ethane in the atmosphere has been increasing by 5% per year. Prior to this, concentrations of the gas had actually been decreasing over a twenty-year period thanks to successful political initiatives. This gas tends to lead to peak ozone levels in the air we breathe and increase the atmospheric lifetime of greenhouse gases. Ethane essentially comes from the exploitation of oil and natural gas. It is also a good indicator of anthropogenic emissions of methane. A multiple study initiated by the University of Liege using measurements and modelling has clearly identified the main cause of the increase of ethane in the atmosphere: the sudden expansion of shale gas exploitation in the US.
A harmful gas for the environment
“One of the beneficial components of the atmosphere is the hydroxyl radical (OH)”, explains Emmanuel Mahieu. “We could call it the detergent of the troposphere because it is a highly reactive molecule which consumes other elements by oxidising them. Among these elements is methane (CH4), for example, which is an even more efficient greenhouse gas than CO2”. Ethane consumes this hydroxyl radical. It becomes oxidised to form carbon monoxide with the carbon it contains. Therefore, the higher the quantity of ethane in the atmosphere, the less hydroxyl radical there is to consume the methane and the longer the lifetime of the latter will be. A second harmful effect concerns the quality of the air, because ethane, during its degradation, promotes the formation of tropospheric ozone (O3). “And we have all heard warnings about ozone peaks in summer. While it is true that the ozone present in the stratosphere protects us from the UV rays of the sun, in the troposphere and the surface air, it is, in excess of a certain threshold, harmful not only for health but also for the development of plants etc.”
(1) Evaluating ethane and methane emissions associated with the development of oil and natural gas extraction in North America, Franco et al, Environmental Research Letters, Vol. 11, April 2016. http://orbi.ulg.ac.be/handle/2268/194574