Marine Power & Propulsion: October 2017
With IMO’s decision last October to make the long-mooted 0.5% global cap on the sulphur content of fuel oil mandatory from the start of 2020, rather than defer implementation until 2025, there is a new urgency to shipowners’ deliberations over which emissions abatement solution to adopt.
The 2015 introduction of a 0.1% limit in designated sulphur (SOx) Emission Control Areas (ECAs) including the North Sea/English Channel, Baltic Sea, North America and US Caribbean, from the previous 1.0% level, has had a profound and seminal influence on operational strategies in specific regions. Now, the weight of tougher legislation is set to be felt everywhere, through the scheduled move from the current 3.5% worldwide sulphur cap to just 0.5%.
Ahead of the IMO announcement regarding the 0.5% global limit, the EU had already agreed that the 0.5% limit would be imposed in 2020 on shipping within 200 miles of member countries’ coasts, where those waters are outside the North Sea, English Channel and Baltic Sea sulphur ECAs and their 0.1% sulphur cap. The EU’s proactive approach has already been demonstrated by its Sulphur Directive ruling, effective from January 2010, prior to the IMO regulations, that all ships had to use fuel with a maximum sulphur content of 0.1% when berthed or at anchor in EU ports.
For its part, China has instigated a programme that will see a 0.5% sulphur limit brought to bear in a steadily increasing number of ports and zones, from initial applications in the Yangtze River Delta, the Pearl River Delta, and the Bohai Sea rim.
The options of using ultra-low sulphur distillate, or burning alternative fuels such as LNG, are the chosen paths of many operators faced with the most stringent regulations designed to combat environmental pollution by sulphur. However, exhaust gas cleaning systems (EGCS), commonly referred to as scrubbers, are increasingly seen as a mature technology, which is generally permitted as an alternative means of compliance. Today, EGCS plant typically takes a more compact form and is more competitively priced than earlier-generation equipment.
Short payback times claimed for new systems, whether for retrofit schemes or newbuild projects, are indicative of the past several years’ improvements in design and installation procedures, and the take-up suggests that the EGCS option is still financially acceptable despite a protracted period of rate weakness in most segments of the shipping industry. The more time a vessel spends within a SOx ECA, the more attractive the return on investment. Uncertainties as to the future price and availability of fuel compliant with the widening reach of tighter regulations have also stimulated growing interest in EGCS.
Against this backdrop, ABS has issued a guide, ABS Advisory on Exhaust Gas Scrubber Systems, on the latest available exhaust gas abatement technologies. The advisory provides detailed guidance on scrubber technology selection, at a time when shipowners and operators are weighing compliance options for their fleets.
While scrubbers offer the potential for lower operating costs by allowing the ship’s machinery to burn less expensive high-sulphur fuels, the overall capital, installation and running costs associated with such systems must be considered on a vessel-specific basis, and assessed in relation to other routes to SOx emission compliance. “Fuel switching, an operational practice in which high-sulphur fuel is used where permitted and lower-sulphur fuel is burned where mandated, has its own complications and risks but should also be considered during an evaluation of fuel compliance options,” counsels ABS.
A vessel’s trading or operating pattern will influence the determination of which type of scrubber would best suit a particular application. “If the ship has an operating profile with a minimum port stay or minimum transit time in ECAs, or there are no restrictions on the discharge water by local or regional regulations, an open loop scrubber may be considered appropriate,” states ABS. “However, if the vessel has long port stays, with an appreciable time spent transiting in ECAs and with minimum time at sea, a hybrid or closed loop scrubber system could be considered. The global IMO fuel sulphur limit scheduled to be reduced to 0.5% in 2020 will influence this decision-making process.”
Besides reviewing regional and local regulations, including monitoring and documentation requirements, the ABS booklet examines the various EGCS concepts, workings and effectiveness, encompassing dry scrubbers and wet open loop, closed loop and hybrid scrubbers and also emerging technologies, such as membrane scrubber systems
