A novel approach to environmental assessment of ships : development of a performance index for ship operation

Abstract

Shipping has a considerable impact on the environment due to operational and accidental pollutant releases. Maritime environmental legislation has tightened in recent years since the introduction of the MARPOL 73/78 regulations, however there is often a significant time gap between when the regulations are adopted and when they legally enter force. The emergence of private voluntary initiatives has occurred in an attempt to bridge this gap, reduce environmental impacts and raise the environmental profile of ships. However, there are inconsistencies in the methodologies used to define ship performance, while the number and diversity of initiatives available for use can cause confusion, hindering progress towards greater sustainability. A critical analysis of existing environmental initiatives in the shipping industry has been conducted, highlighting limitations with regards to applicability, scope, ambition, and integrity of the methodologies adopted. Many of the existing initiatives lack the flexibility to be ship specific and show bias towards certain environmental indicators, and lack the ambition to set stringent standards. Many of the schemes use proxy indicators based on design criteria as a measure of environmental performance rather than actual emissions and discharges. An alternative approach to environmental assessment of ships is proposed which offers a holistic method of assessment, can be applied to multiple vessel types using a broad, relevant scope based on environmental impacts, and assesses performance based on actual emissions and discharges of pollutants to the environment. The proposed method, the VEP index, adopts a risk assessment based methodology and is intended as a holistic framework for assessment of ship environmental performance. The VEP index is rigorously tested using operational data from two case study vessels. The results clearly distinguish which of the vessels performs better environmentally, and highlight the suitability of the index for comparing vessel environmental performance. When compared with other indices used in the shipping sector, the VEP index provides a more accurate assessment of environmental performance based on ships’ operational emissions.