Articles | Volume 10, issue 10
Atmos. Meas. Tech., 10, 3931–3946, 2017

Special issue: Greenhouse gAs Uk and Global Emissions (GAUGE) project (ACP/AMT...

Atmos. Meas. Tech., 10, 3931–3946, 2017

Research article 25 Oct 2017

Research article | 25 Oct 2017

CH4 emission estimates from an active landfill site inferred from a combined approach of CFD modelling and in situ FTIR measurements

Hannah Sonderfeld1, Hartmut Bösch1,2, Antoine P. R. Jeanjean1, Stuart N. Riddick3, Grant Allen4, Sébastien Ars5, Stewart Davies6, Neil Harris7, Neil Humpage1, Roland Leigh1, and Joseph Pitt4 Hannah Sonderfeld et al.
  • 1Earth Observation Science Group, Department of Physics and Astronomy, University of Leicester, Leicester, UK
  • 2National Centre for Earth Observation, University of Leicester, Leicester, UK
  • 3Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA
  • 4Centre for Atmospheric Science, The University of Manchester, Manchester, UK
  • 5Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), CNRS-CEA-UVSQ, Université de Paris-Saclay, Gif-sur-Yvette, France
  • 6Viridor Waste Management Limited, Peninsula House, Rydon Lane, Exeter, Devon, UK
  • 7Centre for Atmospheric Informatics and Emissions Technology, Cranfield University, Cranfield, UK

Abstract. Globally, the waste sector contributes to nearly a fifth of anthropogenic methane emitted to the atmosphere and is the second largest source of methane in the UK. In recent years great improvements to reduce those emissions have been achieved by the installation of methane recovery systems at landfill sites, and subsequently methane emissions reported in national emission inventories have been reduced. Nevertheless, methane emissions of landfills remain uncertain and quantification of emission fluxes is essential to verify reported emission inventories and to monitor changes in emissions. Here we present a new approach for methane emission quantification from a complex source such as a landfill site by applying a computational fluid dynamics (CFD) model to calibrated in situ measurements of methane as part of a field campaign at a landfill site near Ipswich, UK, in August 2014. The methane distribution for different meteorological scenarios is calculated with the CFD model and compared to methane mole fractions measured by an in situ Fourier-transform infrared (FTIR) spectrometer downwind of the prevailing wind direction. Assuming emissions only from the active site, a mean daytime flux of 0.83 mg m−2 s−1, corresponding to a spatially integrated emission of 53.3 kg h−1, was estimated. The addition of a secondary source area adjacent to the active site, where some methane hotspots were observed, improved the agreement between the simulated and measured methane distribution. As a result, the flux from the active site was reduced slightly to 0.71 mg m−2 s−1 (45.6 kg h−1), and at the same time an additional flux of 0.32 mg m−2 s−1 (30.4 kg h−1) was found from the secondary source area. This highlights the capability of our method to distinguish between different emission areas of the landfill site, which can provide more detailed information about emission source apportionment compared to other methods deriving bulk emissions.

Short summary
The waste sector is the second largest source of methane in the UK. However, uncertainties of methane emissions from landfill sites still remain. In this study we present a new approach for the estimation of methane emissions from a landfill site by applying a computational fluid dynamics (CFD) model for precise measurements of methane with in situ Fourier-transform infrared (FTIR) spectroscopy. Different source areas could be distinguished with this method and their emissions were assessed.