Optimization of tugboat propulsion system configurations: A holistic life cycle assessment case study

Abstract

The International Maritime Organization has initialized a strategy to reduce 30% and 50% of carbon dioxide emissions from marine activities by 2030 and 2050 respectively. It is extremely challenging to achieve but innovative cleaner technologies are under research and development to help control and reduce maritime carbon emission. One fact is that the usage of tugboats has been increasing in recent years as huge demands of marine offshore activities (construction, installation and maintenance of renewable islands and wind farms); therefore, the performance of tugboats should be well-evaluated which could be a valuable contribution to maritime emission reduction. This paper focuses on investigating a tugboat’s life cycle performance, specifically comparing different configurations of the propulsion system and selecting an optimal system with the lowest emissions release, costs and hazard impacts. A case study was carried out comparing five different engine configurations with the help of commercial and in-house developed life cycle assessment software in order to comprehensively evaluate the ship performance. Three main life phases, three evaluation flows, four emission categories and three criteria, were under consideration in this study. The results indicate LCA method and the in-house software could help to compare and determine optimal configurations and the engine configuration with three medium size engines is the optimal one which generated lowest emissions equivalent to 15.5 million euros, invested 14.2 million euros and occur a risk impact equivalent to 1.01 million euros. This paper not only provides a case study for the tugboat configuration assessment but also recommends LCA methodology as a general evaluation method for emission reduction technologies who have to meet the extreme requirements of emission control in the next few decades.