Regional variations in green transformation of European ports: A robust quantile stochastic frontier analysis

Facing rising sustainability pressures, green transformation is crucial for European ports to enhance operational capacity and meet environmental targets. This study develops a Green Transformation Index (GTI) to assess the performance of 70 European ports (2006–2018) in balancing operational growth with pollution reduction. We apply a robust composite assessment method combining directional distance functions and quantile stochastic frontier analysis. Analysis reveals three key trends. Firstly, the pace of green transformation closely aligns with environmental regulations; stricter sulfur limits implemented in 2010 and 2015 significantly boosted GTI scores. Conversely, the 2007–2009 financial crisis, causing reduced cargo volumes, temporarily slowed environmental improvement, highlighting economic instability as a constraint. Secondly, significant variation exists in ports’ GTI outcomes. Certain larger ports achieved sustained improvements by proactively investing in efficient infrastructure and pollution control. Others expanded operations more rapidly than adopting green technologies, resulting in lower GTI scores. Similar national-level variations reflect differing policy priorities and technical capabilities. Thirdly, early adoption of pollution control technology proved crucial. Ports installing equipment before new regulations took effect saw swifter gains in environmental performance, while slower adopters maintained lower levels for longer periods. Methodologically, the robustness of the new approach was verified through comparisons with conventional benchmark methods. These findings collectively suggest that effective port green transformation requires tailored governance: ports with lower GTI performance need prioritized support for technology adoption, while top performers require deepened operational coordination to sustain gains.