And if only ethane was the only problem

However, these were only the results of a first model and the intention was to make the observations even sounder. When its origin is well-targeted, ethane is a good indicator of methane emissions. This is another harmful consequence for the atmosphere because exploitation by hydraulic fracturing also releases methane more or less in the same proportions as ethane. This property was useful to the researchers for the creation of a second model simulation.  

“For the first model, which was based on inventories, we used a ‘bottom-up’ technique, from the bottom to the top. We used inventories for calculating the content of the atmosphere. This did not constitute sufficient proof to verify our theories. We needed an extra lever. We wanted to verify this data by means of a “top-down”, approach, from top to bottom. We therefore wanted to record the fluxes by satellite and deduce new inventories from these”. Though direct measurements of ethane fluxes by satellite are not available, methane is very observable from space. It then became possible, based on the quantity of methane emitted from the region identified as the culprit to get an approximate deduction of the ethane flux. “This was the objective of Emily Fischer and her group, also based in Colorado. For this they used the GEOS-Chem model, developed by Harvard. This model takes account of high-definition measurements of methane. The fine resolution available makes it possible to precisely map these fluxes. In parallel with this, they drew up a map of the wells of which there are more than 500,000 today, and they compared this distribution of wells with the intensity of methane emissions. They were therefore able to quantify these fluxes, to attribute them to this activity and deduce an estimate of the ethane emission completely independently of our observations and calculations from the first model. And all our results concur completely. This means that we can confidently point the finger of blame at the American oil industry and the massive exploitation of shale gas because we know where these emissions are coming from and in what quantity”.

Methane, a difficult gas to model

Now, if the emission of ethane has increased by 75% due solely to shale gas exploitation, the methane flux has also increased proportionately given that the overall concentration ratio of these gases is the same. This is not good news either but is also very difficult to observe. “Paddy-fields, marshes, permafrost or cattle to name but a few: there are more than ten natural or anthropogenic sources of methane which must be taken into account when we want to model its emission around the globe. Therefore, if oil activity increases, the amount of methane released into the atmosphere will be less visible than in the case of ethane. The ratio of methane to ethane is a real asset for achieving a more reliable estimate of methane due to the oil industry. We were therefore able to observe that, in 2009, shale gas extraction generated 20 million extra tonnes of methane into the atmosphere. By increasing this flux by 75%, we get a figure of 35 million tonnes emitted in 2014. To put this in context, methane increased by 1% per year up to 2000 before reaching a plateau during 5 years, even though we have yet to understand why. But since then, it has been increasing again by 0.3% per year. We estimate that a third of this increase is due to an increase in gas exploitation in the United States”.

By combining ethane with methane and by associating them with the extraction of natural gas, the publication points to two types of harmful effects which affect both air quality and global warming. But the researchers did not stop there. “We are no longer in the realm of theory. Since our study, it is an incontrovertible truth. We are going to continue studies on a global level and then accelerate proceedings by trying to influence decisions based on our results. Our information should be available and reliable, and we are going to continue working to achieve that. We have a colleague in Colorado who is currently measuring the concentration of gas with a much shorter lifetime at dozens of sites. One of the advantages of these gases is that if they are measured somewhere, this is because their source is very close, while we have detected ethane emissions several thousand kilometres from their source. If the results are significant, we will be better able to identify the harmful effects of shale gas extraction. We are also going to study the data from all the sites in the NDACC network, to obtain a global map of these emissions. We would also like to produce a high-resolution map to better identify the variations in these emissions. For example, we would like to determine if the losses are higher in active wells or in abandoned wells which have been poorly sealed or whether these fluxes are more significant in certain very precise areas in accordance with geological layers. These are all different aspects which we have not been able to discern for the moment. I am not saying that I am asking for a ban on shale gas extraction, but perhaps that, at least, this type of knowledge could lead to more efficient means of extraction in order to drastically reduce emissions”.