Commercial marine emissions and life-cycle analysis of retrofit controls in a changing science and policy environment

This paper considers the technical feasibility of achieving NOx reductions through engine controls on existing oceangoing ships. International transport ships account for most of the NOx emissions from shipping globally and regionally (Corbett and Fischbeck 1997; Corbett et al. 1999). Recently, regulatory efforts to control NOx from ship propulsion have been adopted at the international level (IMO 1998)) along with related efforts at national levels (EPA 1998a; Lemieszewski 1999; National Swedish Maritime Administration 1996; Swedish Port and Stevedores Association 1999). The long working life of modern commercial ships, with world fleet averages greater than 20 years (UNCTAD 1995), implies that new-engine policies have limited value in meeting air-quality objectives in the near term. This has motivated efforts to control shipboard emissions with retrofit technologies. Nine technologies, demonstrated to control NOx from existing engines, are described in terms of their ability to reduce emissions at the lowest life-cycle costs. The costs for these technologies are within the cost range of similar controls proposed for new marine engines and within the cost ranges for various land-based NOx control efforts, suggesting that these are not only technically feasible but also are economically reasonable technologies for pollution control.