Quantifying Farm-Scale Methane Emissions using Downwind Gaussian Plume Modelling with Tracer Correlation

Agricultural methane emissions, from enteric fermentation and manure management, account for approximately 32% of global anthropogenic methane emissions, yet standardized farm- or herd-scale quantification methods remain lacking (Nisbet et al., 2025). Downwind mobile surveys using Gaussian plume modelling for point sources, primarily from oil and gas, and tracer dispersion methods for diffused sources, such as landfills, have been demonstrated to be effective, relatively low-uncertainty approaches for quantifying methane emissions.

Here, we present a computationally efficient framework for quantifying farm-scale methane emissions using Gaussian plume modelling, developed for small- to medium- scale farms in the UK, with ongoing work to extend the approach to grazing cattle. Using a Lagrangian particle model (Oettl & Kuntner, 2024), a virtual upwind point source is assigned to encompass the farm emission footprint (De Visscher, 2014). Gaussian dispersion modelling with Monte Carlo iterations is then applied to downwind vehicle-based methane measurements to derive farm-scale emission estimates.

These estimates are evaluated against results from a simultaneous controlled tracer release conducted by the National Physical Laboratory at the same farm site. We discuss associated uncertainties and highlight future improvements, including process automation, source apportionment, and methods for quantifying emissions from grazing herds.

 

References:

De Visscher, A. (2014). Air Dispersion Modeling: Foundations and Applications. Wiley. https://doi.org/10.1002/9781118723098

Dietmar Oettl & Markus Kuntner. (2024). GRAL: Graz Lagrangian Model (Version 24.11) [Computer software]. Graz University of Technology. https://gral.tugraz.at/

Nisbet, E. G., Manning, M. R., Lowry, D., Fisher, R. E., Lan, X. (Lindsay), Michel, S. E., France, J. L., Nisbet, R. E. R., Bakkaloglu, S., Leitner, S. M., Brooke, C., Röckmann, T., Allen, G., Denier van der Gon, H. A. C., Merbold, L., Scheutz, C., Woolley Maisch, C., Nisbet-Jones, P. B. R., Alshalan, A., … Dlugokencky, E. J. (2025). Practical paths towards quantifying and mitigating agricultural methane emissions. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 481(2309), 20240390. https://doi.org/10.1098/rspa.2024.0390