Environmental efficiency for a cross-section of Spanish port authorities

Shipping has well-documented environmental impacts, among which are greenhouse gas emissions that contribute to climate change and global warming. Measurement of the possibility of ports to reduce emissions by operating more efficiently provides important information for policymakers. In this study we estimate environmental efficiency for a cross section of 28 Spanish Port Authorities observed in 2016 using an output-oriented directional distance frontier with a 'bad output', carbon dioxide (CO2) emissions. We use the non-parametric mathematical programming technique of Data Envelopment Analysis (DEA) to estimate the frontier. Our novel dataset includes information on CO2 emissions obtained for these Spanish Port Authorities using the fleet activity-based emission estimation (bottom-up) methodology. Using ships berthing as output, if all port authorities had been environmentally efficient in providing their services, CO2 emission could have been reduced to an average of 63% of their actual observed levels with a simultaneous increase in good output. When using cargo and passenger traffic as output in order to control for ship characteristics through the output mix, we find that reductions of emissions to 82% of observed levels could be achieved with simultaneous increases in outputs, and reductions to 72 of existing levels if good outputs remain constant.