Towards a high-granularity methane emissions inventory for Colombia – First in situ measurements of solid waste landfills and wastewater treatment plants emissions

Methane’s comparatively short atmospheric lifetime and low mitigation costs compared to other greenhouse gases enhance its potential for near-term climate action. Both mitigation accounting and climate science require accurate emission inventories. Most emission factors and model parameters have been derived from measurements in and at the conditions of developed countries. On the contrary, Global South methane emission measurements are scarce and usually unsystematic. As a result, large discrepancies exist among global databases and with national inventories, e.g., -60% to +180% in the case of Colombia. Under the coordination and support of UNEP’s International Methane Emissions Observatory (IMEO), a multi-sector observation-based baseline inventory is currently being developed for Colombia, involving multiple research groups and measurement platforms and methodologies. Methane emissions from solid waste landfills (SWLF) are the fastest growing in Colombia. We will present preliminary results from an ongoing SWLF and wastewater treatment plant (WWTP) emission measurement campaign (MET-CO). To build accurate observational inventories, we applied a “mixed approach”, which involves measuring the larger-emission SWLFs and WWTPs to about half of the total emissions along with a set of smaller emission facilities that properly map the emission controlling variables. MET-CO includes sniffing with a drone for diffuse emission mapping, flux chamber and channeled biogas mass flow measurements. Carleton University’s Energy & Emissions Research Lab (EERL) will conduct high precision drone-borne measurements for facility and sub-facility wide top-down emission estimation. Chamber-measured methane fluxes of SWLF cells closed over 10 years ago have been very small, from -1.3 (very small sink) to +2.3 mg CH₄ m^-2 day^-1, while a recently covered cell showed very high emissions, +153.5 g CH₄ m^-2 day^-1. Methane enhancements have ranged from ~0.1 to ~17 ppmv in SWLFs, and from ~0.1 to ~600 ppmv in WWTPs, with the larger near sources and enclosed operations. Additional results and a synthesis will be present.