Development of a new gas-flaring emission dataset for southern West Africa

A new gas-flaring emission parameterization has been developed, which combines remote sensing observations using Visible Infrared Imaging Radiometer Suite (VI-IRS) nighttime data with combustion equations. The parameterization has been applied to southern West Africa, including the Niger Delta as a region that is highly exposed to gas flaring. Two 2-month datasets for June-July 2014 and 2015 were created. The parameterization delivers emissions of CO, CO2, NO, NO2 and SO2. A flaring climatology for both time periods has been derived. The uncertainties owing to cloud cover, parameter selection, natural gas composition and the interannual differences are assessed. The largest uncertainties in the emission estimation are linked to the parameter selection. It can be shown that the flaring emissions in Nigeria have significantly decreased by 25% from 2014 to 2015. Existing emission inventories were used for validation. CO2 emissions with the estimated uncertainty in parentheses of 2.7 (3.6/0.5) Tg yr(-1) for 2014 and 2.0 (2.7/0.4) Tg yr(-1) for 2015 were derived. Regarding the uncertainty range, the emission estimate is in the same order of magnitude compared to existing emission inventories with a tendency for underestimation. The deviations might be attributed to a shortage in information about the combustion efficiency within southern West Africa, the decreasing trend in gas flaring or inconsistent emission sector definitions. The parameterization source code is available as a package of R scripts.