Environment - BIMCO Bulletin


ENVIRONMENT March 2020 Are VLSFOs really that bad for the climate? By Lars Robert Pedersen, Deputy Secretary General at BIMCO A report submitted to the International Maritime Organization (IMO) by Finland and Germany suggests the new very low-sulphur fuel oils (VLSFOs), which comply with the 0.50% sulphur limit introduced on 1 January 2020, are bad for the climate. The report claims VLSFOs are predominantly aromatic because of their chemical composition and, when burned in engines, produce elevated levels of climate-forcing black carbon. This article examines that claim and seeks to give a more nuanced view of the issue. Examining and understanding the chemistry of the new VLSFO fuels is a necessary first step The third – and last step – is to compare the situation post 1 January 2020 to that of pre 2020 Let us start with the engine used in the study: a medium-speed, four-stroke diesel (these are predominantly ships’ auxiliary engine). This type runs at relatively high speed and with limited stroke. It means injected fuel has a restricted time to burn and requires better ignition-quality fuel compared with bigger engines to ensure complete combustion. Most fuel oils used by ships are burned in the engines that drive ships’ propellers. A smaller amount is burned in auxiliary engines, driving electricity generators. An even lesser amount is burned in boilers to produce steam for heating purposes. Time is a critical element The vast majority of marine fuel is used for propulsion. Propulsion engines in ships vary significantly but, when we assess the share of each engine type, based on the amount of fuel burned in each, significantly more is used by the slow-speed, two-stroke diesel engines. These large engines operate with long piston strokes and at slow speed – less than 150 revolutions per minute (rpm). This means that oil injected into the combustion chamber and ignited can burn for longer, compared with smaller engines operating at much higher rpm. The time available to burn the fuel oil is critical to avoiding the formation of unburned hydrocarbons and soot, also known as black carbon. In tests, burning fuel oil with a high aromatic content in slow-speed diesel engines has however shown that aromaticity has little influence on the formation of black carbon. Levels of black carbon formation in these engines are also generally below those seen in four-stroke medium-speed models. The ability of a fuel oil to burn fast is linked to its chemical composition, and it is well documented that highly aromatic fuels are not as willing to burn as paraffinic fuel oil. Fuel oils used in ships are usually assessed for their ignition quality by means of their Calculated Carbon Aromaticity Index (CCAI) rating. This value, calculated from the density and viscosity via a complex formula, will normally be between 800 and 880. Fuel-oil testing companies make this calculation as a matter of routine when samples from bunkering are sent for analysis. A CCAI of 860 and above indicates that ignition problems may occur. The high-sulphur fuel oils (HSFO) widely used up until 1 January 2020, before the sulphur regulation came into effect, were normally quite aromatic, with CCAI values between 850 and 870. Further studies needed Now, back to the study we were discussing. It used samples of VLSFO blends made sometime during 2019 – thought then to be representative of those the industry would be bunkering now to comply with the new sulphur regulation. The fuels were then burned as described above in a medium-speed, four-stroke diesel engines, and the exhaust gases analysed for black carbon emission. Unsurprisingly, the study found a correlation between aromaticity and combustion quality, with the highly aromatic fuels emitting higher levels of black carbon. Little can be concluded from the study, other than the fact that burning highly aromatic fuels in medium-speed engines can give rise to increased black carbon emissions. This is nothing new. What we cannot do is assume the conclusion will be the same when it comes to black carbon emissions from all engine types burning compliant fuels that were delivered post 1 January 2020 under the new sulphur regulation. Therefore, examining and understanding the chemistry of the new VLSFOs is a necessary first step on the way to making black carbon conclusions post 1 January 2020. Step two is to investigate black carbon emission levels from large bore, slow-speed, two- stroke engines, in addition to the medium-speed, four-stroke diesel engines (auxiliary engines) used in the study, for correlation between fuel oil aromaticity and black carbon formation. The third – and last step – is to compare the situation post 1 January 2020 to that of pre 2020. Once these steps have been taken and results published, I would not be in the least surprised if the conclusion is that black carbon emissions from ships have actually dropped because of the shift to 0.50% VLSFO. Connect with BIMCO Photo (top): iStock / doranjclark Facebook Twitter Linkedin YouTube Lars Robert Pedersen has over 30 years’ experience in the shipping industry, which combined with his insight into IMO makes him a respected authority on technical and regulatory issues. Robert was appointed Deputy Secretary General of BIMCO in early 2010 and leads a team of experts responsible for BIMCO’s technical, security and operational activities. This includes direct membership services and active involvement in regulatory developments related to ship operation at international and regional levels. Before joining BIMCO, he had a career at A.P. Moller-Maersk handling regulatory affairs and technical management of the Maersk fleet of container ships after having spent 7 years as a seagoing officer. Robert holds an unlimited Chief Engineer’s licence.