Thursday, July 19, 2018 | ISSN 0719-241X

Scrubbing the way to cleaner air

Fuel exhaust cleaning technology for the 2020 sulphur cap
Edition of June 06, 2017

IMO’s 2020 sulphur cap to reduce sulphur dioxide emissions to a minimum of 0.5% has the whole shipping industry looking at alternatives to comply with the regulation in record time. 

According to energy and commodities information provider S&P Global Platts, the most popular option among carriers is equipping vessels with exhaust gas cleaning systems, or scrubbers. By installing a system that sprays alkaline water into a vessel’s exhaust, the ship-owner can remove sulfur dioxide and other unwanted chemicals from its emissions. The technology has long been used in land-based power plants, though it remains less well tested at sea. 

Scrub, scrub, scrub 

The main advantage of scrubbers is that they allow ship-owners to continue burning fuel oil while remaining compliant with the new global sulfur cap. But this comes at a cost: the ship-owner needs to find up to US$6 million in advance to install the equipment on each vessel. 

Over time, that capital will be saved in lower fuel bills – and the speed of return on investment will be determined by the price differential between high sulfur fuel oil and 0.5% sulfur bunkers, says the expert analysis from S&P Global Platts. Yes, scrubbers are expensive, but LNG or even methanol could be even more costly. 

A lack of shipyard space worldwide may limit the uptake of scrubbers before 2020, as the global fleet is currently also gradually being retrofitted with ballast water management systems to comply with new regulations. Some are hoping scrubber installation prices will drop in the coming years before 2020 as more manufacturers enter the market, while others are waiting to check how effective the systems are before committing to the investment. 

A fit for everybody 

Ship-owners looking at scrubbers will also need to consider which type is most suitable for their needs. Open-loop scrubbers take in naturally alkaline seawater and then flush the discharge out to sea, while closed-loop systems add caustic soda to raise the alkalinity of the water being used, and have the option of the discharge being retained to dispose of at port. Hybrid systems with the option to work in either open- or closed-loop modes are also available. 

Closed-loop scrubbers come with a much higher operating cost, with the expense both of the caustic soda constantly being added and of the discharge disposal. Open-loop scrubbers also tend to be considerably cheaper to install, with a price tag as much as US$800,000 lower than closed-loop versions in some cases. 

But open-loop systems come with a regulatory risk: lawmakers concerned about ocean acidification may seek to prevent ship-owners from simply removing the sulfur from their emissions and then dumping it in the sea. 

The current technology is suitable for removing sulfur and nitrogen from emissions and with some modifications may be able to remove most particulate matter. But if restrictions on carbon emissions come into force, the current scrubber technology would not be a cost-effective means of complying. 

By MundoMaritimo

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