Using remote sensing to detect, validate, and quantify methane emissions from California solid waste operations

Solid waste management represents one of the largest anthropogenic methane emission 14 sources. However, precise quantification of landfill and composting emissions remains difficult due 15 to variety of site-specific factors that contribute to landfill gas generation and effective capture. 16 Remote sensing is an avenue to quantify process-level emissions from waste management facilities. 17 The California Methane Survey flew the Next Generation Airborne Visible/Infrared Imaging 18 Spectrometer (AVIRIS-NG) over 270 landfills and 166 organic waste facilities repeatedly during 19 2016-2018 to quantify their contribution to the statewide methane budget. We use representative 20 methane retrievals from this campaign to present three specific findings where remote sensing 21 enabled better landfill and composting methane monitoring: (1) Quantification of strong point source 22 emissions from the active face landfills that are difficult to capture by in situ monitoring or landfill 23 models, (2) emissions that result from changes in landfill infrastructure (design, construction, and 24 operations), and (3) unexpected large emissions from two organic waste management methods 25 (composting and digesting) that were originally intended to help mitigate solid waste emissions. Our 26 results show that remotely-sensed emission estimates reveal processes that are difficult to capture in 27 biogas generation models. Furthermore, we find that airborne remote sensing provides an effective 28 avenue to study the temporally changing dynamics of landfills. This capability will be further 29 improved with future spaceborne imaging spectrometers set to launch in the 2020s.