They help ships meet IMO 2020 emissions standards yet the debate around ‘scrubbers’ is not straightforward as they are banned in some parts of the world.

As most of us know only too well, shipping and air quality are intertwined. Poor air quality caused by international shipping – much of it emissions from sulphur compounds, although there are others – has been implicated in thousands of deaths globally each year, although estimates vary.

It’s a startling situation, and one that led the international regulatory and shipping community to act by cutting down on damaging fuel emissions, with the industry getting a long lead time to meet IMO 2020 regulations implemented on 1 January 2020.

Changes to Annex VI of MARPOL [agreed in 2016] saw permitted levels of sulphur oxides (SOx) from ship emissions cut substantially from 3.50% to 0.50% m/m (mass by mass) outside Emission Control Areas (ECAs); with the 0.10% limit inside ECAs unchanged.

The good news is that this could save lives – even before emerging research showing that the SARS-COVID-19 virus may affect those it strikes more severely in areas where air quality is poor.

Navigating the IMO2020 challenges

Yet, if the IMO2020 requirements seem straightforward, why does the industry keep referring to the new regulation as a ‘big challenge’?

There are many reasons why compliance is somewhat complex, including choosing which solution is best for each ship, assessing the practical implications of the regulations, and balancing return on investment.

1. Use low sulphur fuel oil

The vast majority of ships now comply this way with refineries producing residual blends to meet the new sulphur limit. There have, however, been a number of quality issues and a need to avoid incompatibility issues between fuels from different deliveries.

2. Choose alternative low or zero sulphur fuels

Another compliance route is using low or zero sulphur fuel oil such as methanol, LNG, and biofuels.  Ships able to use these can meet the IMO2020 requirements, but this only applies to 1-2% of the global fleet.

3. Install an EGCS, or ‘scrubber’

EGCS – exhaust gas cleaning systems often known as ‘scrubbers’ – use either seawater or freshwater, or chemicals, to remove remove sulphur oxides from the exhaust gases of the ship’s engines and boilers.

The ship is allowed to burn heavy fuel oil high in sulphur content but harmful oxides are removed from the emissions to a level equivalent to the required fuel oil sulphur limit. 

According to the Exhaust Gas Cleaning Systems Association (EGCSA), an industry association representing scrubber manufacturers, nearly 4,000 ships have installed EGCS to comply with the regulations, an estimated 6 to 7% of the global fleet.

But plunging oil prices in the wake of the pandemic, and continued uncertainty over whether or not they will recover, have thrown the cost benefits of choosing a scrubber into question by sharply reducing the cost differential between heavy fuel oil and lower sulphur blends.

The great scrubber debate

Yet just months into the new regulatory landscape, another debate around scrubbers is swirling.

Of the two types of scrubber systems – open and closed-loop – the open-loop system discharges the washwater direct into the sea as opposed to an enclosed system where it can be stored and taken ashore.  

Discharged water into the sea must, rightly, meet specific criteria such as having a not-too-acidic pH of no less than 6.5 at 4m away from the ship’s hull. There are also strict limits on the discharge of Polycyclic Aromatic Hydrocarbons (PAHs), substances which are ‘bio-accumulative’ and make their way into the underwater food chain and stay there.

While not unique to scrubbers, PAHs have been a concern for some time. The theory is that as they accumulate, they steadily sicken the ecosystem.

In 2019, a Joint Group of Experts on Scientific Aspects of Marine Environmental Protection (“GESAMP”) was formed, at IMO’s request, to look into the subject of open-loop scrubber discharge. They presented their findings to the IMO Sub-Committee on Pollution Prevention and Response (PPR) at its 7th session this year.

Is discharging any waste water to the sea a good idea?

Even meeting the discharge criteria, Singapore, neighbouring Malaysia, and others, think not. Singapore law prohibits discharging washwater from ‘open-loop’ scrubber systems in its waters, making the list of compliance challenges even longer.

While several port authorities around the world have said they have no intention to ban ‘open-loop’ scrubbers in their waters, just how many ports might follow Singapore is uncertain.

In the meantime, and until further research is carried out that might persuade administrations to change regulations on scrubber discharge (either for or against), shipowners and operators can still consider an EGCS a suitable compliance option with improvements in monitoring technologies providing some level of assurance.

One thing is sure, and that is that some degree of certainty is welcome.

Find out more:

Members can debate this topic on Nexus and read the IMarEST explainer on open-loop scrubbers.