Open-Loop Scrubbers Hub

What are Scrubbers?

Exhaust gas cleaning systems, commonly known as ‘scrubbers’, are systems installed on ships to remove certain substances from exhaust gases. They have become prevalent in recent years as the International Maritime Organization (IMO), the UN body that governs international shipping, introduced a global cap on the amount of sulphur content used in shipping fuels in 2020. The maximum amount of sulphur permitted, without a scrubber, is not 0.5% across the world, although the east coast of the UK is within an Emissions Control Area (ECA) with a sulphur limit of 0.1%.

Scrubbers are an alternative option for complying with the IMO sulphur cap, on the condition that they are as effective in reducing emissions as using low sulphur fuel. The UK Government supported this position at the IMO.

The BPA has prepared a 3-page briefing on scrubbers for those wishing to learn more about the technology and the port industry’s response to their use.

What does the science say on Open-Loop Scrubbers?

As IMO 2020 and scrubber installations are recent developments, there have been few long-term studies into the environmental impact of discharged washwater in port areas specifically. There have been several broader studies into the environmental impact of washwater, with some conflicting results. The BPA have produced a literature review of studies that have assessed the environmental impact of scrubber discharge water.

The BPA sought surveyed our port members in early 2024 on their management of open-loop scrubbers in harbour areas. Ports of all types (cargo, ferry, cruise, etc.), sizes, and locations across the UK restrict open-loop scrubbers, and there is no uniform approach. We found that 94% of ports surveyed had some form of management – though their implementation methods varied.

Some ports receive few vessels with scrubbers so decisions can be made on a case-by-case basis, and others enforce blanket restrictions on scrubbers. Whilst 94% of port respondents stated they manage scrubbers in some way, this is not necessarily representative of the UK as a whole due to our sample size (18 harbour authorities responded) and respondent bias (ports with restrictions were more likely to respond to our survey). For these reasons, we have decided to keep our results internal but we will maintain our own database of restrictions around the UK.

How are other countries managing ports Open-Loop Scrubber use?

Many countries and ports are restricting their use – the International Chamber of Shipping has a webpage with global scrubber bans and restrictions, and the International Council on Clean Transportation mapped restrictions in more detail in June 2023. It found that 93 measures have been implemented in 45 countries. The paper, however, does not give an accurate representation of scrubber restrictions in UK ports. It also may be somewhat outdated, as this is an evolving landscape with imperfect information.

It is the BPA’s view that more research is required on the impact of discharged contaminants on port marine areas, particularly those with different tidal flow conditions and washwater dilution levels. Some studies indicate that discharged washwater has a limited impact on marine environments and aquatic life. Concerns still exist about its cumulative effects on sediment pollution over time in low flow environments and sensitive marine areas.

We will update this page when appropriate. Contact for more information.