Environmental baseline monitoring for shale gas development in the UK: Identification and geochemical characterisation of local source emissions of methane to atmosphere

David Lowry; Rebecca E Fisher; James L France; Max Coleman; Mathias Lanoisellé; Giulia Zazzeri; Euan G Nisbet; Jacob T Shaw; Grant Allen; Joseph Pitt; Robert S Ward

doi:10.1016/j.scitotenv.2019.134600

Environmental baseline monitoring for shale gas development in the UK: Identification and geochemical characterisation of local source emissions of methane to atmosphere

Sci Total Environ. 2020 Mar 15:708:134600. doi: 10.1016/j.scitotenv.2019.134600. Epub 2019 Nov 3.

Authors

Affiliations

¹ Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK. Electronic address: d.lowry@rhul.ac.uk.
² Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK.
³ Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK; British Antarctic Survey, High Cross, Madingley Rd, Cambridge CB3 0ET, UK.
⁴ School of Earth and Environmental Science, University of Manchester, M13 9PL, UK.
⁵ British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK.

PMID: 31767337
DOI: 10.1016/j.scitotenv.2019.134600

Abstract

Baseline mobile surveys of methane sources using vehicle-mounted instruments have been performed in the Fylde and Ryedale regions of Northern England over the 2016-19 period around proposed unconventional (shale) gas extraction sites. The aim was to identify and characterise methane sources ahead of hydraulically fractured shale gas extraction in the area around drilling sites. This allows a potential additional source of emissions to atmosphere to be readily distinguished from adjacent sources, should gas production take place. The surveys have used ethane:methane (C2:C1) ratios to separate combustion, thermogenic gas and biogenic sources. Sample collection of source plumes followed by high precision δ¹³C analysis of methane, to separate and isotopically characterise sources, adds additional biogenic source distinction between active and closed landfills, and ruminant eructations from manure. The surveys show that both drill sites and adjacent fixed monitoring sites have cow barns and gas network pipeline leaks as sources of methane within a 1 km range. These two sources are readily separated by isotopes (δ¹³C of -67 to -58‰ for barns, compared to -43 to -39‰ for gas leaks), and ethane:methane ratios (<0.001 for barns, compared to >0.05 for gas leaks). Under a well-mixed daytime atmospheric boundary layer these sources are generally detectable as above baseline elevations up to 100 m downwind for gas leaks and up to 500 m downwind for populated cow barns. It is considered that careful analysis of these proxies for unconventional production gas, if and when available, will allow any fugitive emissions from operations to be distinguished from surrounding sources.

Keywords: Baseline surveys; Carbon isotopes; Ethane; Methane; Mobile measurement.