Quantifying fugitive methane emissions in Queensland, Australia

Summary Methane is the second most important greenhouse gas, contributing about 25% to the global warming experienced to date. In Australia, fugitive methane emissions are estimated to be the second largest component of the overall methane emissions. Due to their very nature, the quantification of fugitive methane emissions is non-trivial and existing frameworks e.g. based on equipment-specific, sometime-calibrated, emission ‘factors’ are not necessarily representative for Australian conditions. To overcome these issues and to improve fugitive emissions monitoring, estimation and subsequent reporting, top-down approaches are becoming increasingly popular. These approaches involve measuring changes in atmospheric methane concentrations over space and time, mostly using remote sensing techniques. Based on these concentration measurements in space and time, emission rates (fluxes) are then calculated using complex (typically ‘inversion’) algorithms. This conversion from measured concentrations to calculated emissions rates is error prone and current approaches struggle to achieve satisfactory correlations between inferred and true emissions rates.