Comparative analysis between different methods for calculating on-board ship's emissions and energy consumption based on operational data.

With the aim of more reliably measuring ships' fuel consumption and emissions several different estimation methods have been put forward and are in use but there is ongoing debate still on the best way to measure maritime emissions. Fuel and emissions monitoring are already a common practice in the shipping industry. But there are currently neither harmonised guidelines nor legal requirements that clearly define the method and the rules to follow to monitor on-board fuel consumption for each situation during navigation. In this context, this article describes and compares four existing methods (EPA, IMO, Jalkanen and MAN) for calculating energy consumption and emissions, and presents a more realistic method, based on a case study. The purpose is to examine the differences between all of these methods, in order to propose the most suitable method of obtaining the data needed for better energy management, and a method that can be applied to any type of ship. The case study was carried out on Ro-Pax ships, comparing these four different methods through the application of a bottom-up integrated system approach. The study describes in detail and applies the most complete methodology for calculating energy consumption and emissions during cruising, operating in a Speed Reduction Zone (SRZ), manoeuvring and berthing. Application of the new improved method proposed in this paper could be the first step in implementing operational measures for detecting both abnormal high emissions and abnormal fuel consumption. The application of this method does not, in itself, reduce fuel use or improve efficiency, but it should be the necessary first step to establish uniform operational measures that will improve the management of energy on board ship and monitor accurately the performance of the fleet.

The influence of the waterjet propulsion system on the ships' energy consumption and emissions inventories.

In this study we consider the problems associated with calculating ships' energy and emission inventories. Various related uncertainties are described in many similar studies published in the last decade, and applying to Europe, the USA and Canada. However, none of them have taken into account the performance of ships' propulsion systems. On the one hand, when a ship uses its propellers, there is no unanimous agreement on the equations used to calculate the main engines load factor and, on the other, the performance of waterjet propulsion systems (for which this variable depends on the speed of the ship) has not been taken into account in any previous studies. This paper proposes that the efficiency of the propulsion system should be included as a new parameter in the equation that defines the actual power delivered by a ship's main engines, as applied to calculate energy consumption and emissions in maritime transport. To highlight the influence of the propulsion system on calculated energy consumption and emissions, the bottom-up method has been applied using data from eight fast ferries operating across the Strait of Gibraltar over the course of one year. This study shows that the uncertainty about the efficiency of the propulsion system should be added as one more uncertainty in the energy and emission inventories for maritime transport as currently prepared. After comparing four methods for this calculation, the authors propose a new method for eight cases. For the calculation of the Main Engine's fuel oil consumption, differences up to 22% between some methods were obtained at low loads.

Towards an integrated environmental risk assessment of emissions from ships' propulsion systems.

Large ships, particularly container ships, tankers, bulk carriers and cruise ships are significant individual contributors to air pollution. The European Environment Agency recognizes that air pollution in Europe is a local, regional and transborder problem caused by the emission of specific pollutants, which either directly or through chemical reactions lead to negative impacts, such as damage to human health and ecosystems. In the Marine Strategy Framework Directive 2008/56/EC of the European Parliament emissions from ships are mentioned explicitly in the list of pressures and impacts that should be reduced or minimized to maintain or obtain a good ecological status. While SOx and NOx contribute mainly to ocean and soil acidification and climate change, PM (particularly ultrafine particles in the range of nanoparticles) has the potential to act more directly on human and ecosystem health. Thus, in terms of risk assessment, one of the most dangerous atmospheric aerosols for environmental and human health is in the size range of nanoparticles. To our knowledge, no study has been carried out on the effects of the fraction that ends up in the water column and to which aquatic and sediment-dwelling organisms are exposed. Therefore, an integrated environmental risk assessment of the effects of emissions from oceangoing ships including the aquatic compartment is necessary. Research should focus on the quantitative and qualitative determination of pollutant emissions from ships and their distribution and fate. This will include the in situ measurement of emissions in ships in order to derive realistic emission factors, and the application of atmospheric and oceanographic transportation and chemistry models.