A study by an environmental research group has concluded that countries should ban or restrict discharge from exhaust gas scrubbers.

The International Maritime Organization rules that came into force in January capped it at 0.5%, forcing shipowners to use low-sulphur fuel oil or install scrubbers that put the sulphur from burning high-sulphur fuel oil (HSFO) into the ocean.

Despite IMO approval, the non-profit International Council on Clean Transportation (ICCT) said discharges from the devices, which are on about 5% of the world fleet, should be restricted or prohibited.

"We recommend individual governments continue to take unilateral action to restrict or prohibit scrubber discharges from both open-loop and closed-loop systems," the group said.

"We also recommend that the IMO focus on harmonising rules for scrubber discharges including where, when, and even if those discharges should be allowed, and to do so with urgency."

Not for newbuildings

In the study funded by federal government agency Environment and Climate Change Canada, ICCT also suggested that the IMO consider outlawing them as a compliance option for newbuildings.

"This is because we found that using HSFO with scrubbers is not equivalently effective at reducing air pollution compared to using lower sulphur fuels, such as MGO," the non-profit said.

"Additionally, scrubbers of all kinds (open, closed, and hybrid) directly contribute to ocean acidification and water pollution, whereas lower sulphur fuels do not."

ICCT also recommended that scrubbers be prohibited as a way to comply with the Canadian portion of the North American emission control area (ECA) because they are not as effective at lowering air pollution as ECA-compliant fuels.

It also suggested prohibition of all scrubber discharges in Canadian ports, internal waters, and territorial seas because they contribute to acidification and water pollution that can negatively affect marine life.

Not great for the Great Lakes

"Within Canada, this includes scrubber discharges in the Great Lakes, as well as British Columbia and the St Lawrence Estuary, where endangered species like the Southern Resident killer whales and belugas already suffer from high levels of contamination, including from PAHs and heavy metals," ICCT said.

Scrubber technology, used for decades on factory smokestacks, caused such a deep divide in shipping over sea-life impact that scrubber advocacy groups formed amid staunch opposition from environmentalists and some owners.

The findings from this federally-funded study are alarming,” said Tzeporah Berman, international programmes director for US environmental group Stand.earth.

“Scrubbers don’t stop air pollution and they make ocean pollution worse.”

Calls to scrubber advocacy organisations Exhaust Gas Cleaning Systems Association and Clean Shipping Alliance 2020 and Canadian laker owner Canadian Steamship Lines were not immediately returned.

Heavy metals

The ICCT study pointed out that scrubbers do lower sulphur dioxide, but carcinogenic contaminants such as polycyclic aromatic hydrocarbons and heavy metals are dumped into the sea as wash water.

"Regarding air emissions, we found that using scrubbers can substantially reduce sulphur dioxide emissions but carbon dioxide, particulate matter, and black carbon emissions were higher when using HSFO with a scrubber than using MGO," the report said.

This story has been amended to reflect that the study was carried out by International Council on Clean Transportation (ICCT), rather than the Canadian government, and that the study called for a ban on or restrictions of scrubber discharges.