Determinants of scrubber adoption in container shipping: A time-varying survival analysis

The International Maritime Organization's (IMO) 2020 global sulphur cap has accelerated the adoption of scrubbers in the container shipping sector. However, research on when to install scrubbers and how key factors affect installation remains limited. This study addresses that gap by applying a time-varying survival analysis to investigate the determinants of scrubber adoption in container ships. Using data from 4492 container ships built between 2000 and 2023, we examine how ship characteristics (e.g., age, size, fuel type), market features (e.g., shipbuilder and ship operator), and policy environment (e.g., IMO regulation, flag) influence the timing and likelihood of scrubber adoption. The results show that by the end of 2023, approximately 27.5 % of container ships have been equipped with scrubbers, with the adoption rate significantly accelerating after 2019. Among all influencing factors, fuel type determines the major part of a ship's operating cost and shows the strongest statistical association with scrubber adoption, highlighting the centrality of cost-benefit tradeoffs in compliance decisions. Ship age is the second important factor and shows a negative impact, while IMO regulation is the third important factor. Ship size, operator, flag, and builder also have significant but more moderate influences. The results also reveal important temporal dynamics in scrubber technology diffusion. The effect of IMO regulation decays exponentially, while the effect of fuel type decays linearly, indicating that scrubber adoption decisions have complex temporal dynamics. These findings extend our understanding of scrubber technology diffusion in maritime transportation, highlighting the dynamic nature of adoption drivers and the interaction between technical, economic, and regulatory factors.