To achieve compliance with the sulphur cap, simply switching to a low sulphur fuel at January 2020 will not be enough. High sulphur fuel oil (HSFO) is primarily based on residual fuel and these tend to stick to the inside of fuel tanks and pipelines forming layers of sludge and sediments.
The accumulated layers of existing sludge in the fuel tanks and pipelines may contaminate the new fuel loaded, rendering the fuel non-compliant and pushing emissions above the 0.50% sulphur cap. Cleaning this out will require exhaustive efforts – either manually which is risky, expensive and time-consuming, or with specialised fuel treatments (chemical additives).