A Framework for the Environmental Benchmarking of Airports Focusing on Achieving CO2 Neutrality

Air transport is contributing to climate change, among other activities through the emission of CO2. While climate relevant emissions from airlines have been in the focus of public and political awareness for a number of years now, this only partly applies to these emissions of airports. However, some airports such as Sydney, Frankfurt, Istanbul, Munich and Hamburg are now pursuing the goal of climate neutrality in the coming years. This paper provides a framework to benchmark airports along with CO2 emissions. We review the technological measures that airports can take in order to become CO2 neutral. Furthermore, we review the literature and find that there are 41 parameters across seven categories which can be used by airports in order to reduce or mitigate CO2 emissions. Our results indicate that conventional benchmarking models cannot be used in order to model the production process of airports along with CO2 emissions as an externality. This is because these models do not obey the materials balance principle and the first and second laws of thermodynamics. In the non-parametric data envelopment analysis (DEA) framework, our findings show that methodological extensions such as the by-production approach, the natural and managerial disposability approach and factorially determined multiple equation models are the best models. In the parametric stochastic frontier analysis (SFA) framework, we find that multiple equation models can be used with the production sub-technology being estimated using a standard translog distance function while the emissions-generation sub-technologies can be estimated using Leontief type distance functions. We also find that index number total factor productivity can be applied provided the availability of a factor price for CO2 emissions. The application of our findings in future research would close a research gap as, to the best of our knowledge, only two papers in the literature are focussing on airport benchmarking with CO2 emissions both of which have not used the methodological extensions mentioned above.