Application of open-path TDL analysers for determination of methane and ammonia emissions from livestock facilities

Increasing levels of atmospheric methane and its role in global warming has led to increasing demand to verify emission estimates from agricultural sources. Ammonia is of concern due to environmental impacts of downwind deposition and the role of ammonia in aerosol formation. Cattle confined in livestock facilities represent a major source of agriculture generated methane while the manure associated with these facilities is responsible for over 80% of agriculture's ammonia emissions. Emission measurement from complex sources demands a technique sufficient to capture the temporal and spatial variability associated with animal activity on a whole-farm basis. Measurement of an emissions plume using infrared gas analysers or gas chromatography can often be problematic in field situations, and may not allow for continuous measurement or sufficient spatial coverage. For this study, two portable, open-path, tunable diode laser (TDL) analyzers were used to monitor the subject gases. This allowed for continuous measurements of atmospheric methane and ammonia downwind of livestock facilities over a path length sufficient to capture the emissions plume. In conjunction with a backward Lagrangian dispersion model, these sensors allowed for methane and ammonia flux estimation from various livestock facilities in Southern Alberta.