27 Sep 2022
27 Sep 2022
Status: this preprint is currently under review for the journal ACP.

Flaring efficiencies and NOx emission ratios measured for offshore oil and gas facilities in the North Sea

Jacob T. Shaw1, Amy Foulds1, Shona Wilde2, Patrick Barker1, Freya Squires2,a, James Lee2,3, Ruth Purvis2,3, Ralph Burton4, Ioana Colfescu4, Stephen Mobbs4, Stéphane J.-B. Bauguitte5, Stuart Young2, Stefan Schwietzke6, and Grant Allen1 Jacob T. Shaw et al.
  • 1Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
  • 2Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO10 5DD, UK
  • 3National Centre for Atmospheric Science, University of York, York, YO10 5DD, UK
  • 4National Centre for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 5Facility for Airborne Atmospheric Measurements FAAM 125, Cranfield University, Cranfield, UK
  • 6Environmental Defense Fund, Berlin, Germany
  • anow at: British Antarctic Survey, Natural Environment Research Council, Cambridge, CB3 0ET, UK

Abstract. Gas flaring is a substantial global source of carbon emissions to atmosphere, and is targeted as a route to mitigating the oil and gas sector carbon footprint, due to the waste of resources involved. However, quantifying carbon emissions from flaring is resource intensive, and no studies have yet assessed flaring emissions for offshore regions. In this work, we present carbon dioxide (CO2), methane (CH4), ethane (C2H6), and NOx (nitrogen oxide) data from 58 emission plumes identified as gas flaring, measured during aircraft campaigns over the North Sea (UK and Norwegian) in 2018 and 2019. Median combustion efficiency, the efficiency with which carbon in the flared gas is converted to CO2 in the emission plume, was 98.4 % when accounting for C2H6, or 98.7 % when only accounting for CH4. Higher combustion efficiencies were measured in the Norwegian sector of the North Sea compared with the UK sector. Destruction removal efficiencies (DREs), the efficiency with which an individual species is combusted, were 98.5 % for CH4, and 97.9 % for C2H6. Median NOx emission ratios were measured to be 0.003 ppm per ppm CO2 and 0.26 ppm per ppm CH4, and the median C2H6 : CH4 ratio was measured to be 0.11 ppm ppm-1. The highest NOx emission ratios were observed from Floating Production Storage and Offloading (FPSO) vessels, although this could potentially be due to the presence of alternative NOx sources onboard, such as diesel generators. The measurements in this work were used to estimate total emissions from the North Sea from gas flaring, of 1.4 Tg yr-1 CO2, 6.3 Gg yr-1 CH4, 1.7 Gg yr-1 C2H6, and 3.9 Gg yr-1 NOx.

Jacob T. Shaw et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-679', Anonymous Referee #1, 18 Oct 2022
  • RC2: 'Comment on acp-2022-679', Anonymous Referee #2, 19 Oct 2022

Jacob T. Shaw et al.

Data sets

Methane Observations and Yearly Assessment (MOYA) Euan Nisbet

Demonstration Of A Comprehensive Approach To Monitoring Emissions From Oil and Gas Installations (AEOG) Jonathon Crosier

Jacob T. Shaw et al.


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Short summary
Flaring is used by the oil and gas sector to dispose of unwanted natural gas. However, few studies have assessed the efficiency with which the gas is combusted. We sampled flaring emissions from offshore facilities in the North Sea. Average measured flaring efficiencies were ~98 % but with a skewed distribution including many flares of lower efficiency. NOx and ethane emissions were also measured. Inefficient flaring practices could be a target for mitigating carbon emissions.