The case for the end of scrubbers on ships

By Enzo Cremers, Andrew Dumbrille & Elissama Menezes | Opinion | Originally published in Canada’s National Observer

The documented impacts of scrubber discharge from ships include harmful algae blooms, nitrogen loading, exposure to heavy metals, heightened ocean acidification and both direct and indirect impacts to human health.

File photo by: Rochelle Baker / Canada's National Observer.

In the 1970s and 1980s, the transboundary acid rain crisis — driven largely by sulphur oxide (SOx) and nitrogen oxide (NOx) emissions — forced Canada and the United States into coordinated action to reduce cross-border air pollution and protect ecosystems and public health.

Today, Canada is once again at the center of the SOx debate. The shipping industry has long been a major source of SOx emissions, prompting the International Maritime Organization (IMO), the sector’s global regulator, to introduce sulphur limits for marine fuels in 2020. Rather than driving a straightforward transition to cleaner fuels, these rules have opened the door to a controversial compliance mechanism: exhaust gas cleaning systems, commonly known as “scrubbers.” 

Scrubbers allow ships to continue burning the dirtiest marine fuels by ‘scrubbing out’ the sulphur dioxide from its exhaust. However, that scrubbed out sulphur has to go somewhere. The wastewater from the scrubbing process is dumped directly into the ocean, shifting the pollution from the air to the water. The documented impacts of scrubber discharge include harmful algae blooms, nitrogen loading, exposure to heavy metals, heightened ocean acidification and both direct and indirect impacts to human health, especially for communities relying directly on marine resources. 

In addition to creating a water contamination problem, scrubbers also fail to deliver many of the broader environmental and health benefits that come with a shift to cleaner fuels. For instance, black carbon — a short-lived health and climate pollutant with disproportionate impacts in the Arctic — largely passes through scrubber systems. When deposited on snow and ice, it accelerates melting; when inhaled, it contributes to respiratory and cardiovascular diseases. Switching from heavy fuel oil to cleaner distillate fuels complies with sulfur limits while also cutting black carbon emissions by roughly 80 per cent. Scrubbers, by comparison, slightly increase fuel consumption and therefore carbon dioxide emissions. In effect, they function as a loophole that enables continued reliance on highly polluting fuels while shifting the pollution burden to marine ecosystems.

Recognizing the impacts of scrubbers, Transport Canada launched a public consultation in 2024. Environmental NGOs, Indigenous and community organizations and researchers all submitted comments warning of the damaging impacts of continued scrubber use. 

The results of the consultation are clear: Canadians are concerned about the impact of scrubbers on coastal waters, human health, ecosystems and communities — and they want action. Nearly all (98 per cent) respondents supported some form of restriction on scrubbers or scrubber discharge, with “many” respondents calling for restrictions “as soon as reasonably possible.”

Jurisdictions around the world — and even within Canada — are already moving ahead. Five Canadian ports have restricted scrubber discharges; Denmark, Finland and Sweden are a year into their scrubber water discharge bans; and 15 countries on the North-East Atlantic will implement theirs by July next year.

With international and regional scrubber restrictions progressing, marine stakeholders demanding action and mounting evidence of environmental harm, federal restrictions on scrubbers are overdue. Continued delay from Transport Canada is not a neutral choice. It translates into ongoing air and ocean pollution in sensitive areas, including fishing grounds, coastal communities, tourism sites, Indigenous use and harvest territories and the climate-vulnerable Arctic. 

There is no safe threshold for scrubber discharge. For that reason, scrubbers should be banned from Canadian waters. Transport Canada should act on its own findings and the overwhelming consensus across the country and move with urgency to safeguard Canada’s oceans and communities.

Enzo Cremers, Andrew Dumbrille and Elissama Menezes are with Equal Routes, a non-profit centering communities and rights holders to create a sustainable and equitable marine shipping sector.