Scrubber (Exhaust Gas Cleaning System)
A Scrubber, or Exhaust Gas Cleaning System (EGCS), is equipment fitted to a ship that removes sulphur oxides (SOx) from the engine exhaust, allowing the vessel to comply with sulphur limits (such as IMO 2020) while continuing to burn cheaper high-sulphur fuel oil. It works by spraying the exhaust with water (often seawater), which absorbs the sulphur before the gas is released.
Scrubbers come in open-loop (discharging the wash water to sea), closed-loop (retaining and treating it) and hybrid types. Their business case is the price spread between high- and low-sulphur fuel: the fuel saving repays the capital cost over time, so scrubber economics rise and fall with that spread. They are controversial environmentally — open-loop discharge is banned in some ports and waters — and add equipment to operate and maintain. Scrubbers are one of the two main compliance paths (versus switching fuel) under the sulphur cap, and a significant capital and operational decision in ship management.
The scrubber is a bet on the fuel-price spread — spend capital to keep burning cheap high-sulphur fuel and pocket the difference. That bet, plus tightening rules on wash-water discharge, makes scrubbers a live capital and compliance decision in ship management. Understanding them is understanding one of the two roads through the sulphur cap.
Why fit a scrubber instead of switching fuel?
To keep burning cheaper high-sulphur fuel while complying with sulphur limits; the fuel saving repays the scrubber's cost, depending on the fuel-price spread.
Why are open-loop scrubbers controversial?
They discharge wash water to sea, which is banned in some ports and waters over environmental concerns.