Exhaust Gas Cleaning Systems (EGCS) are commonly referred to as scrubbers. These systems effectively wash the exhaust gas to remove sulphur dioxides and particulate matter. Post 2020, vessels operating an EGCS can continue to legally burn fuels with a sulphur content of greater than 0.5%.
Systems are categorised as open loop, closed loop or hybrid.
Open loop systems: Water is taken from the sea and pumped into the scrubber wash tower. The natural alkalinity in seawater means it does not need chemicals to be added prior to scrubbing. This method can be used in most seas around the world where alkalinity levels are high. The effluent is then treated and discharged back to sea.
Closed loop systems: Seawater or freshwater is treated with an alkaline chemical before entering the wash tower to scrub the exhaust gases. Wash water is re-circulated and any losses made up with additional water. A small amount of the wash water is bled-off to a treatment plant before discharge to sea, or they can be run in ‘zero discharge’ mode where the effluent is held in a tank.
Hybrid systems: Hybrid systems can operate in either open or closed loop mode. Depending on design, they may operate with either freshwater or seawater when in closed loop mode.
Moderate capex (US$3-5m) with expected payback period to be reasonably short
Expected low fuel costs - the difference in price between high sulphur residuals and compliant MGO is expected to increase significantly post 2020
The lower fuel costs may make the vessel more attractive to time charterers
Systems and equipment require lot of space
High power demands resulting in 3-5% fuel penalty
High maintenance demands and there are concerns on reliability which could result in transitory non-compliance
The long term viability of EGCS could be impacted by any future legislation on effluent discharge standards
The availability of high sulphur fuels post 2020 is unknown and some refineries could divert streams elsewhere if not profitable
Shipowners may come under pressure from charterers to install EGCS
The time required to retrofit EGCS on an existing vessels could take several weeks