Recent and Projected Trends in Global Civil Aviation Fleet Average NOxEmissions Indices

Abstract

Aircraft emitted oxides of nitrogen (NOx) contribute both to climate change and air quality degradation. The trend of higher gas temperatures, caused by engine design choices seeking lower fuel consumption and achieve more complete combustion, has the adverse effect of increasing NOx formation, which might however be compensated by improved combustor designs. The tradeoff between lowering NOx or CO¬2 emissions is an important consideration in mitigating the environmental impacts of aviation, and, and in context of the industry’s environmental targets and forecasts, quantifying the technological trend taking place can provide an indication of future emission totals. In this study, we estimate bottom-up global fleet average aviation fuel burn and NOx emissions for the years 2005 and 2018 and extrapolate their totals to 2030, 2040, and 2045 with current air traffic and engine performance forecasts. Average NOx emission indices are evaluated for different aircraft classes at each year considered, and their changes over time are discussed together with a sensitivity analysis on the assumptions made.