Clearing the Air: The Role of Scrubbers on Ships

With the increasing concerns and regulations around global emissions from vehicles of all types, cruise ships, and the larger maritime industry at large, has taken to scrubbers as a way to get old ships up to par.

As the world continues to seek cleaner and more sustainable alternatives for fuels, the maritime sector faces its own unique set of challenges. One such challenge is reducing emissions from ships already in service that cannot be re-engined. Enter “scrubbers” – innovative devices that are changing the game by helping ships clean up their act while navigating the high seas. In this blog post, we’ll dive into the world of scrubbers on ships, exploring their purpose, types, and environmental impact.

A Breath of Fresh Air: Understanding Scrubbers

Scrubbers, in the context of maritime technology, are emission control systems designed to reduce pollutants released into the atmosphere from ships’ exhaust gases. These pollutants primarily include sulfur dioxide (SO2) and particulate matter – substances known to contribute to air pollution, acid rain, and respiratory illnesses.

The Science Behind Scrubbers: How They Work

At their core, scrubbers work by employing a combination of chemistry and physics to remove pollutants from exhaust gases. The process typically involves spraying a water-based alkaline solution (often referred to as a “scrubbing agent”) into the exhaust stream. This solution reacts with the sulfur dioxide in the gases to form less harmful compounds, such as sulfate salts. These salts are then captured and removed from the exhaust gas stream, resulting in a significant reduction in harmful emissions.

Types of Scrubbers: Open and Closed Loop

There are two main types of scrubber systems commonly used on ships: open loop and closed loop. Let’s take a closer look at each:

1. Open Loop Scrubbers: In this system, seawater is used as the scrubbing agent. The exhaust gas is passed through a tower where it comes into contact with seawater. The sulfur dioxide reacts with the alkaline properties of the seawater to form sulfites and sulfates. The resulting solution is then discharged back into the sea, following regulatory guidelines.
2. Closed Loop Scrubbers: In this design, a separate circuit is used for the scrubbing process. The scrubbing solution is recirculated through the system, which includes a neutralization stage where the captured pollutants are neutralized. This closed-loop process reduces the discharge of pollutants into the environment, as the scrubbing solution is not released into the sea.

Environmental Considerations and Benefits

The adoption of scrubbers by the maritime industry has sparked debates about their environmental impact. While scrubbers help reduce sulfur emissions and mitigate air pollution, the discharge of scrubbing solution into the sea has raised concerns about its effects on marine ecosystems. Regulations and guidelines are in place to address these concerns and ensure that discharges are within safe limits.

Despite these considerations, scrubbers offer several notable benefits:

1. Reduced Air Pollution: Scrubbers significantly lower emissions of sulfur dioxide and particulate matter, thus contributing to cleaner air and improved public health.
2. Compliance with Regulations: Scrubbers enable ships to meet stringent emissions regulations, such as the International Maritime Organization’s (IMO) 2020 sulfur cap regulations, which limit the sulfur content of marine fuels.
3. Cost-Effectiveness: Scrubbers allow ships to continue using traditional high-sulfur fuels, which can be more cost-effective than switching to low-sulfur alternatives.

The Path Forward: Striking a Balance

The adoption of scrubbers on ships reflects the maritime industry’s ongoing efforts to strike a balance between environmental responsibility and operational efficiency. Scrubbers offer a viable solution for reducing emissions from existing fleets while allowing ships to continue their operations without drastic fuel changes.

As the technology continues to evolve, there is potential for further improvements in scrubber efficiency and environmental impact. The maritime industry, in collaboration with regulators and environmental experts, remains committed to finding sustainable solutions that minimize the ecological footprint of shipping while maintaining the essential flow of global trade.

In the end, scrubbers symbolize the industry’s determination to sail towards a greener and more sustainable future, where the air we breathe and the oceans we traverse are both better protected. While the ultimate end-goal is of course a zero-discharge ship, that will take perhaps a decade or two until we are there. That will involve fuel cells and battery storage packs on a monumental scale. By retrofitting scrubbers, it allows current ships to carry on as always while select new ships get LNG or ammonia fueled engines as that technology comes online.