Marine Engineering: Design and Operation for Environmental Sustainability
Anthony Paul ROSKILLY*
ABSTRACT
This paper discusses issues concerning the environmental sustainability of shipping and some of the main marine engineering issues forcing change and the development of new technologies. The social and legislative trends indicate a demand for a continued reduction in powering and propulsion engine exhaust emissions whilst attempting to maintain high efficiency, maintainability and reliability.
Recent research and developments in piston engine, gas turbine and alternative heat engine technologies are presented in this paper which attempt to address these demands, some of which will become common place if early potential and promise can be commercially harnessed.
Key Words: Environmental sustainabiiity, marine engineering, emissions, efficiency, powering and propulsion
* Department of Marine Technology
Armstrong Building, Newcastle University, Newcastle-upon-Tyne, NE1 7RU, UK
FAX: +44-191-222-6719, E-mail: tony.roskilly@ncl.ac.uk
1. INTRODUCTION
Environmental sustainable development seeks to improve the quality of human life without undermining the quality of the natural environment. It is essential for engineers to assess the current and future motivation and expectations for environmental sustainability [1]. The most cost effective design of an engineering system is relatively easy to assess when taking into account labour and material costs but excluding any environmental impact. However, environmental 'costs' need to be taken in to account and rationalised with financial costs.
In the face of tightening safety and environmental legislation there remains the demand to increase reliability, improve efficiency and reduce maintenance requirements. Also, with the range of ship types and their applications constantly expanding, operators require machinery systems with higher power density and greater flexibility in location and operation, all at lower cost. Whilst improvements to existing technologies will meet some of these requirements, radical changes in the powering and propulsion plants in operation will be necessary to improve environmental sustainability.
Heightened governmental and public environmental awareness has, in recent years, been recognised by engine designers and necessitated the need for a reduction of harmful emissions. Objectives have always been aimed at maximising thermal efficiency, maintainability and reliability. However, these must now be maintained in parallel with developments to significantly reduce the level of specific exhaust emissions, most notably, NOx.
2. ENVIRONMENTAL IMPACT OF THE MARINE INDUSTRY
Assessment of environmental impact can be achieved by the analysis of shipping's contribution to global pollution levels and to carry out a cost/benefit assessment of pollution reduction measures. Johnsen et al [2] modelled the world fleet main propulsion emissions for 1996 and concluded that CO2, SO2 and NOx, constituted 2%, 5% and 7% of global emissions of these species respectively.
Alternatively, life cycle analysis (LCA) studies can be carried out to investigate the environmental impact of shipping as a means of transport [2][3]. Climate change, acidification, toxic contamination, local air pollution, noise, energy consumption, and land use are some of the environmental impact categories which can be used to study the environmental damage sustained through different modes of transportation. To evaluate the importance of these impact categories and to produce a single comparative index, weighting of the categories is required based on ethical and ideological values.
These LCA studies have and will continue to help legislators, regulating bodies, operators and researchers focus on the important issue and concerns that need to be addressed by the change in operation and the application of alternative technology. A LCA of a complete transport chain can be carried out and it is possible to optimise the environmental performance of that chain with detailed knowledge of the machinery systems. Further research is investigating the optimisation of economic and environmental performance of transport chains.
The movement of cargo and passengers will involve a chain of transportation means over the complete journey. The distance travelled for alternative transport chains will not be the same and therefore environmental performance should be evaluated between the start and end point of the chain. Functional units for the environmental impact may be per ton, per m3 or per cargo unit for cargo and per passenger for the movement of people [3].
Using the ExternE valuation method to weight the impact categories it was estimated that particulates, NOx, and CO2 caused more than 90% of the environmental damage regardless of technology or fuel used. The costs estimates indicated that NOx emissions are significantly higher and should be given higher priority than CO2. Using the EPS valuation, based on societies willingness to pay that includes both pollution and resource consumption, produces a different result and indicates that fuel consumption and CO2 emissions are the most important issues followed by particulates, NOx and SOx in that order. These valuation models do not take into account pollution location and if included then the environmental impact would reduce since a significant proportion of ships pollution occurs in open waters.
A holistic or "cradle to grave" approach is required to analyse the full impact of the marine industry. The cradle to grave analysis for a vessel and its marine equipment would include construction, operation, and decommissioning phases of its life. A comprehensive assessment would include the examination of natural resource utilisation. From various case studies it is evident that CO emissions and solid waste production are the most significant problems as a result of vessel construction, taking into account steel production. However, by far the greatest environmental impact is found during a vessels operational phase, with the energy resource consumption and combustion emissions associated with its powering and propulsion causing the greatest environmental impact. During the decommissioning of a vessel the most significant detrimental environmental problem is associated with the solid waste produced. A negative CO contribution through the steel recycling can offset a large proportion produced during construction [2].
