Mobile Observations and quantification of Methane Emissions to inform National Targeting, Upscaling and Mitigation (MOMENTUM)

Consecutive record-breaking atmospheric CH4 growth rates of 15 and 17 ppb in 2020 and 2021 respectively, have increased the challenge of meeting the Paris Agreement and the Global Methane Pledge. The 2021 UN Global Methane Assessment report highlighted the need for large cuts in methane emissions this decade to slow global temperature rise. Recommendations for remediation targets are urgently required. The UN suggest that within the main source categories the following reductions are possible: 61% from fossil fuel production, distribution and use, 48% from waste processing and waste-to-energy generation, 22% from agriculture.

The UK inventory suggests that CH4 anthropogenic emissions have decreased significantly since 1990, but have remained static for the last 4 years. Our recent mobile measurement campaigns have highlighted potential for further reduction in emissions, particularly in gas distribution infrastructure. Mobile studies are also well-placed to identify so-called super-emitters. Rapid identification and prioritisation for repair or replacement can thus significantly and quickly impact total national emissions, as nations continue to transition to less carbon intensive activities.

The UK aims to meet its 2050 net zero targets with the development of 'green' or 'blue' energy, e.g. waste-to-energy or hydrogen production. An improved quantification of CH4 emissions from these emergent sectors is essential, but little is known about the lifecycle emissions of these sectors at present, making accurate Net Zero assessments impossible. We have already shown that CH4 measurements from biogas plants can be substantial and should be represented as point sources in the national inventory. Modelling of the UK and Ireland network of continuous methane measurement sites has allowed validation of the total UK emission from the inventory. What it does not do is validate emissions from individual source sectors or pinpoint emissions.

Given these knowledge gaps how do we ensure the accuracy of the UK's methane inventory in order to prioritise mitigation strategy and Net Zero policy? MOMENTUM aims to develop mobile measurement solutions to do this. It is essential to validate source sector emissions to provide further targets for methane reduction. This requires methodology for wide spatial coverage, but at measurement heights where emissions from individual source categories can be resolved in the complex environments of the UK, rather than from satellites or aircraft. We will develop individual CH4 source category emission quantification solutions for academic and industry/regulatory end users, following a series of experimental field campaigns using vehicle and UAV platforms to calibrate measurements and validate methodologies.

In summary the project will:
a) Test multiple instrument responses to different meteorological, instrumental and logistical parameters during mobile measurement, applying these to a range of flux models for different controlled emission release rates and distance from source.
b) Develop specific measurement and flux solutions for each source category from these results and data for co-emitted species (CO2, ammonia, ethane) and isotopes.
c) Test the validity of these solutions at known energy infrastructure and agricultural sites, and in a complex source environment with multiple sources (landfill, agriculture, biogas plant, oil refinery and gas infrastructure).
d) Use the validated methodology to survey a representative population of the main inventory emission categories (agriculture, waste, fossil fuel).
e) Upscale the emissions to national level to identify discrepancies in the inventory, and provide knowledge to fill inventory gaps, particularly for emerging sources.
f) Provide policy targets for emissions mitigation on the road to 'Net Zero' in collaboration with BEIS and other project partners.