Mobile observations of methane to constrain agricultural greenhouse gas emissions

Methane is a potent greenhouse gas that also degrades air quality over decadal time scales. Increases in anthropogenic sources of methane have contributed about a quarter of observed global warming since the preindustrial era. New York State is actively pursuing climate action goals that include the reduction of greenhouse gas emissions, including methane. Thus, locating, quantifying, and monitoring methane sources is critical to set realistic goals and ensure accountability. Here we present mobile observations conducted in central New York to better understand regional methane sources. Using high precision gas sensors mounted on a mobile platform, we performed 6 campaigns to measure concentrations within and around two farms located within the Finger Lakes Region. Methane observations and meteorological measurements were combined to create mass balance estimates of methane emission fluxes from various areas of the farm (barns, waste storage). From our observations within barns, we estimate emission rates of 5-24 kg per barn per day from enteric fermentation. Observations near manure storage indicate emission rates of comparable magnitude, 12-17 kg per day. Our results show that emissions from both the cow and its waste are important considerations for greenhouse gas accounting.