The air quality impacts of pre-operational hydraulic fracturing activities

Hydraulic fracturing (fracking) is a short phase in unconventional oil and natural gas (O&G) development. Before fracking there is a lengthy period of preparation, which can represent a significant proportion of the well lifecycle. Ex-tensive infrastructure is delivered onto site, leading to increased volumes of heavy traffic, energy generation and con-struction work on site. Termed the pre-operational period, this is rarely investigated as air quality evaluations typically focus on the extraction phase. In this work we quantify the change in air pollution during pre-operational ac-tivities at a shale gas exploration site near Kirby Misperton, North Yorkshire, England. Baseline air quality measure-ments were made two years prior to any shale gas activity and were used as a training dataset for random forest (RF) machine learning models. The models allowed for a comparison between observed air quality during the pre-operational phase and a counterfactual business as usual (BAU) prediction. During the pre-operational phase a signif-icant deviation from the BAU scenario was observed. This was characterised by significant enhancements in NOx and a concurrent reduction in O3, caused by extensive additional vehicle movements and the presence of combustion sources such as generators on the well pad. During the pre-operational period NOx increased by 274 % and O3 decreased by 29 % when compared to BAU model values. There was also an increase in primary emissions of NO2 during the pre-operational phase which may have implications for the attainment of ambient air quality standards in the local surroundings. Unconventional O&G development remains under discussion as a potential option for improving the security of supply of domestic energy, tensioned however against significant environmental impacts. Here we demon-strate that the preparative work needed to begin fracking elevates air pollution in its own right, a further potential disbenefit that should be considered.

Automated summary

Hydraulic fracturing, or fracking, is a short phase in unconventional oil and gas development with a significant pre-operational period that often goes unnoticed in air quality evaluations. This study quantifies the change in air pollution during the pre-operational phase at a shale gas exploration site in England. The results show that the preparative work for fracking significantly increases NOx emissions and reduces O3 levels compared to the business as usual scenario. This finding highlights the potential adverse effects of fracking on air quality and should be taken into consideration.