Research and analysis

Ambient air monitoring at shale gas sites framework for design of adaptive monitoring regimes - summary

Published 17 December 2021

Applies to England

1. Chief Scientist’s Group report summary

This project has developed a framework for designing ambient air quality monitoring programmes at shale gas sites. The Environment Agency regulates these sites in England and issues permits that may require operators to monitor local air quality. A framework is needed so the monitoring is auditable, consistent, proportionate to risks and costs, and adjustable for changes.

A structured approach to the design of monitoring can help to detect, investigate and improve adverse air quality impacts from shale gas sites. It can also help to make monitoring efficient and effective, so that costs to industry are justified, and public confidence in regulation is upheld. If monitoring is planned systematically, time, effort and uncertainty can be saved when permits are agreed between industry and regulators like the Environment Agency.

1.1 Assessing emissions and impacts

To develop the framework, it was necessary to assess the activities at shale gas sites that may result in emissions to air. It was also necessary to establish what the main pollutants might be and what concentrations they may reach in the environment. The first step was to consider:

• what activities occur during different phases of operation in the lifecycle of a shale gas site;
• what pollutants are emitted in each phase.

The shale industry in England is at an early stage of development, so there is currently little information from measuring its emissions and air quality impacts directly. Impacts were therefore estimated by preparing emissions data for a hypothetical, but typical, shale gas site. Two sets of emission data were prepared, covering different rates of site development and degrees of emission control, in order to investigate how these differences may affect air quality. The emissions data were combined with typical weather data and inputted to a computer model in order to predict the concentrations of air pollutants in the local environment.

The model predicted that some pollutants could exceed ambient air quality standards near the site for both sets of emission data, unless there were further emission controls (which would be necessary for compliance). The relevant pollutants were nitrogen dioxide, and non-methane volatile organic compounds if the compounds all occur as benzene. The predicted concentrations of pollutants were used to inform the design of monitoring regimes.

1.2 Monitoring options

In order to identify options, the reasons for monitoring ambient air quality were reviewed and the specifications and costs of different methods were summarised. Three levels of monitoring effort were defined (reduced, routine and enhanced) which reflected different potential levels of impact and monitoring cost. The main pollutants considered for monitoring were nitrogen dioxide, methane, non-methane volatile organic compounds and particulates.

The activities and potential air quality impacts of a shale gas site change as it develops. Five phases of activity were defined: baseline, exploration, drilling, hydraulic fracturing and extraction. The information prepared on monitoring methods and levels of effort was used to outline options for ambient air quality monitoring during each phase.

1.3 Monitoring framework

The framework shows which monitoring options are appropriate for different situations. Each situation is assessed for risk, based on factors such as:

• the size of the site (number of wells);
• the impacts predicted by modelling;
• the level of background pollutant concentrations.

The framework allows appropriate monitoring methods to be chosen for each pollutant and situation, and to be adapted as a site develops. The framework was trialled in 5 case studies that showed how monitoring regimes can be designed for hypothetical, but realistic, situations, and adapted for changes.

1.4 Conclusions

The main pollutants released from shale gas activities have been identified for different phases through the lifecycle of a site. Emission estimates and a computer model have been used to predict the impacts on local air quality from different phases. The model predicted that, unless there were further emission controls, some pollutants may exceed air quality standards - particularly nitrogen dioxide. The impacts come notably from mobile machinery burning diesel fuel, which may need further investigation.

The study developed and trialled a framework to support proportionate decisions on monitoring of ambient air quality at shale gas sites. The framework is an outline scheme that needs refining and trialling in ‘real world’ situations. However, its structure, methods and information should already be useful to regulators and industry, for example to inform discussions on environmental monitoring plans in permits.

1.5 Publication details

This summary relates to information from the following project:

• Report: SC170014/R Title: Ambient air monitoring at shale gas sites: framework for design of adaptive monitoring regimes
• Project manager: Roger Timmis, Chief Scientist’s Group
• Research contractor: Ricardo Energy and Environment

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.