What Are Ship Scrubbers and How Are They Polluting Our Oceans?

Shipping is just one of the many problems our oceans are struggling to deal with in the 21st century. As globalisation and consumerism rise, so does the number of vessels creeping across our vast oceans and sadly, noise pollution, collisions with animals and oil spills increase too. However, there is now another rapidly increasing source of pollution coming from ships, one that is under many of our radars.

Let’s take cruise ships as an example and focus on those vessels travelling from the west coast of America to Alaska, one of the most popular holidays for Americans this year. This journey sees cruises travel along the Canadian coast for two or three days before arriving at remote and stunning Alaskan destinations. Yet each year it is estimated that 147 billion litres of harmful waste is discharged by ships making this voyage, the equivalent of 59,000 Olympic swimming pools. Most of this waste is a concoction of toxic sewage, greywater from sinks, showers and laundry facilities and finally bilge water, which is the oily water that collects at the bottom of the ship. This all sounds bad enough yet now more pollution is being dumped into our oceans via ship scrubbers.

Scrubbers are a mostly unheard of term for those not in the industry but these devices are installed in order to remove exhaust gases. Simply, scrubbers sit in the funnels or exhaust stacks of ships where seawater is then used to scrub the pollutants, such as sulphur oxide and nitrogen oxide, off the exhaust. During this process, other particulates, such as oil and fuel are likely to be collected in the water which then, more often than not, is discharged straight into the sea in the form of a chemical cocktail of toxic substances. This whole ill thought out procedure has only arisen recently since the Internal Maritime Organisation (IMO) announced its goals to lower ships’ sulphur emissions that were entering the atmosphere. This target is set to reduce air pollution which negatively impacts the health of communities living on the coast in busy shipping areas but unfortunately, it seems that the pollution has simply shifted from the air to the sea. In order to meet the new global sulphur cap, ships have been urged to use cleaner low sulphur fuel which is much more expensive than traditional fuel. However, the IMO has allowed ships to also take equivalent measures to reduce sulphur emissions which has led to many installing cheaper scrubbers which allow them to burn cheap dirty fuel and leave the pollution hidden amongst the waves. It is thought that an astonishing 10 gigatonnes of scrubber waste is dumped into our oceans each year, almost the equivalent weight of all the cargo which is transported by ships each year.

Going back to the Alaskan cruise ships, each vessel is thought to averagely expel 200 million litres of waste from scrubbers on their typical one week trip, a number which feels impossible to imagine. Of course, there is the option to take this wastewater back to ports and dispose of it properly but many vessels use an open loop system which sees polluted water directed straight out to sea rather than to a collection tank. Shockingly, some ships even discharge this waste whilst parked up in port as they still need to burn fuel to run their swimming pools, air conditioning and a number of other luxury facilities.

For Canada, this issue is particularly bad as their dumping laws are a lot less strict than US laws which govern the waters of Washington, where many of the ships depart from, and Alaska. In Alaska, permission has to be sought to discharge ship waste whilst Washington has a 6,000 kilometre square no discharge zone to protect its waters. As soon as ships enter Canadian waters, they are free to dump untreated sewage only 12 miles from shore, whilst greywater and treated sewage can be released only 3 miles from the coast. Not only is this bad news for coastal communities but for the many species which live in these rich waters. There are several marine protected areas in this patch of ocean, each with their own specific regulations yet most don’t prohibit operational waste discharges by ships and even if they did, pollution from just outside the protected boundary can easily be carried in on the current.

The effect this toxic waste has on wildlife is obviously dramatic although not yet fully understood. Threatened populations of sea otters and orcas call the waters off Canada home whilst the Scott’s Island marine national park has one of the largest congregations of stellar sea lions in the world. Each spring, millions of seabirds descend on the area, including 90% of Canada’s tufted puffins and half of the world’s Cassin’s auklets, making this area of important ecological significance. Yet now sulphur, nitrogen and a mix of heavy metals are frequently being released into the local waters and whilst the skies may be clearer, it is making the future for marine life look even more bleak. With this being a relatively new source of pollution, scientists are still in debate as to the exact effects it could have on our marine ecosystems. Some say that whilst several of these pollutants may be safe on their own, the complex mix of chemicals together can be incredibly dangerous and create new compounds with unknown effects. Meanwhile, others believe that it is not the overall volume we should be concerned about but the individual components and their potential toxicity.

So far though, several negative effects on our oceans have already been observed. Observations from Alaskan fishermen have reported sailing through 30 miles of foamy yellow waters after cruises have passed through, whilst studies in the North Sea have shown that zooplankton are being negatively affected by ship scrubber water. These tiny organisms are the very base of the food web, providing food for not only important fish stocks such as cod and herring which we heavily rely on but also some of our oceans’ biggest creatures, such as baleen whales. Other investigations into the contents of the wastewater have found that it contains heavy metals which accumulate in the food chain as well as dangerous PAHs which are linked to cancer and reproductive dysfunction in marine mammals. Scrubber water can also be up to 100,000 times more acidic than seawater, meaning it could have a devastating impact on our corals which are likely to become bleached and dead if subject to high levels of acidity. This is particularly concerning as the Great Barrier Reef sees 32 million tonnes of wastewater dumped on it by ships each year as it lies on a major shipping route for coal.

Often, busy shipping routes contain the highest levels of scrubber pollution, including the Baltic Sea, the North Sea and the Caribbean. The most polluted ports in the world include Vancouver, Barcelona, Southampton and George Town in the Cayman Islands. Some of these areas, such as Vancouver, are now banning open loop scrubber systems to help try and protect their waters but as of yet, the laws governing this type of pollution around the world are simply not tight enough and not enforced properly. This is particularly concerning as the fragile Arctic begins to open up to the world of shipping. In February 2021, a Russian gas tanker made history by navigating the northern sea route between China and Siberia in mid-winter, something that is now possible due to reduced sea ice cover. With climate change only set to accelerate ice melt, this vulnerable part of the planet with unique wildlife is set to be opened up to the pollution and problems that shipping brings. Already, shipping traffic in the Arctic has increased by 25% in only six years and alongside this, soot and exhaust fumes increase too. This has a particularly dangerous effect here as when soot or black carbon as it is known, lands on ice it makes the surface of it dark grey or black. This means that the sun’s heat is then absorbed by the ice, rather than reflected, serving to further accelerate ice melt. The IMO has urged ships to use cleaner fuels in the Arctic to reduce this build up of black carbon but this is currently only a voluntary measure until 2029, when heavy fuel oils will be banned for all ships.

It is always sad to learn about a new type of pollution which is leaching into our oceans, especially one which is as potentially dangerous as this but with knowledge comes power. As a consumer and citizen you can make choices based on the type of world you want to live in, whether that is rallying against governments and businesses for causes you truly believe in, opting to buy local products to reduce your contribution to the global shipping industry or giving the ocean a helping hand when you can.

By Neve McCracken-Heywood