Satellite-based Methane Emission Estimates of Western Canada Using Simple Mass Balance Method and Quantifies Oil and Gas Sector Contribution

Canada's three western provinces (Saskatchewan, Alberta, and British Columbia) are responsible for 70% of 2015 national total methane gas emissions, even though these provinces only account for 28% of Canada's population, mainly because of large emissions from oil and gas operations in these provinces. However, recent studies reported that official estimations of methane emissions from the oil and gas sector are underestimated, thus the uncertainty in the emission inventory is problematic for regulation of methane emissions. In this study, the latest SCIAMACHY IMAP (v7.2; 2003-2009) and GOSAT OCPR (v7.0; 2009-2015) data products of column averaged dry-air mole fractions of atmospheric methane (XCH₄) are analyzed to derive time-averaged XCH₄ maps and detect regionally elevated methane over several regions of western Canada. We use a previously-developed mass balance method in which satellite XCH₄ retrieval is being applied to estimate annual methane emissions and their corresponding uncertainties in the source regions. The relative contributions from the oil and gas sector and biogenic sources to the total estimated emissions are assessed. For estimating methane emissions not associated with oil and gas sector such as enteric fermentation, manure management, landfills, waste water handling, and agricultural soils we use EDGAR (v4.3.2) data products (0.1°×0.1° spatial resolution), and emissions from local wetlands are estimated from previously published data sets. The difference between total and biogenic sources might be attributed to methane emissions from the oil and gas sector and are compared with recent studies focusing on observation-based methane emissions from the oil and gas sector in Canada. This simple mass balance approach allows a quick assessments of methane emissions from the rapidly growing oil and gas sector in western Canada, and also enables us to assess discrepancies between official emission inventories and other data sets.