Reducing Pollutant Emissions from Maritime Traffic : The CAPNAV Project Led by ESTACA Researchers Offers Initial Solution Pathways
The CAPNAV project (Characterization of particulate emissions from ships) has come to an end after more than three years of study by ESTACA’s air quality research teams. The project highlights reductions in fine particle emissions achieved on commercial ships by using Liquefied Natural Gas (LNG) propulsion.
Maritime traffic generates pollutant emissions (sulfur and nitrogen oxides and fine particles) that have a major impact on the health of coastal populations. As the maritime sector lags behind in terms of atmospheric emission standards, controlling these emissions is a major environmental and health issue. In order to obtain tangible data on the levels of pollutants generated by the French maritime fleet, an ESTACA research team was commissioned by ADEME in 2019 to quantify the emissions generated by maritime transport and test a range of technical solutions to limit pollution. The aim was to gain a better understanding of the nature and concentration of particulates emitted by two types of engines: one running on marine diesel (MDO), the other on liquefied natural gas (LNG). The second objective was to quantify emissions according to engine operation: underway, maneuvering and dockside. Following more than three years of measurements on ships and laboratory studies, the CAPNAV project (Characterization of fine particle emissions from ships), has just published its conclusions.
Creation of an on-board instrumentation chain for better understanding of fine particle emissions
The main benefit of the CAPNAV project was to have developed for the first time an on-board measurement chain. Various instruments, initially developed in the laboratory, were housed in watertight casings for outdoor use in sometimes extreme conditions. They were loaded on two passenger and freight vessels: the Fromveur 2 operated by Penn Ar Bed (marine diesel propulsion) on the daily service to the Ponant islands, and the Salamanca operated by Brittany Ferries (LNG propulsion) on the weekly service between Cherbourg, Ireland and Spain. Several weeks of on-board measurements in the ships’ stacks, synchronized with the recording of ship parameters (speed, engine load), were used to quantify particulate emissions, which vary according to whether the ship is maneuvering or sailing. The instrumentation chain made it possible to take long samples for physical-chemical analysis and carry out statistical analysis of emissions to produce a map of particulate emission factors. The on-board instrumentation could be used in future studies.
Hybrid propulsion systems to limit emissions in coastal areas and when manoeuvring
Measurements taken on the Fromveur 2, a marine diesel-powered vessel, first highlighted the much higher emission rates during maneuvers than during navigation. The challenge is to reduce emission levels around ports, where residents live. A diesel additive solution was also tested. Thus, only led to a 20% reduction in nitrogen oxide (NOx) emissions under part-load conditions, and had no impact on improving particulate emissions. The data collected in the CAPNAV project show that to limit particulate emissions on this type of vessel, the best scenario is to move towards hybrid marine diesel/electric architectures so as to be able to use “zero emission” electric mode during port maneuvering and conventional propulsion at cruising speed.
Liquefied Natural Gas (LNG) propulsion: one solution for reducing fine particle emissions
The second vessel studied, the Salamanca, had the advantage of a dual-fuel engine, and could run on either diesel or liquefied natural gas. The ESTACA research team carried out a comparative study of particulate emissions between the two types of fuel. An exploratory study of cabin and deck air quality was also carried out. The results were indisputable: stack measurements showed a 50-fold reduction in particulate emissions when using LNG compared with marine diesel.
New project to continue measurements
The results obtained by the researchers will used in a new project, EMINAV (Emissions from Vessels), also backed by the ADEME, which aims to assess more comprehensively both gaseous and particulate pollutant emissions. Two types of engines will be studied: conventional marine engines powered by marine diesel without pollution control systems, and engines running on liquefied natural gas. Methane slip concentration levels will be looked at closely. Methane is a powerful greenhouse gas, and unburnt methane emissions are a weak point in LNG-powered engines.
The project is being carried out in partnership with ITM Atlantique, as well as the shipowners Penn Ar Bed and Brittany Ferries, Chantiers de l’Atlantique and ECOGAS.
