Ship Scrubbers Move Sulphur into the Sea: Cleaning Marine Fuel Ashore with Arbok-BC

Since 2020 the sulphur content of marine fuel has been capped at 0.5%, and at 0.1% in special areas. Shipowners meet the cap in two ways: by buying low-sulphur fuel, which costs about 100 USD per t more than high-sulphur fuel oil, or by burning cheap high-sulphur fuel and washing the exhaust in a scrubber. Roughly 6,400 ships now carry scrubbers, and about 80% of them are open-loop, so the sulphur is moved from the funnel into the sea. Wash water discharged this way is of the order of 10 billion t a year, comparable with the 11 billion t of cargo the fleet carries. Restrictions on scrubber discharge are arriving: from 1 July 2027 in ports and internal waters of the North-East Atlantic for open-loop units, and from 2029 for closed-loop units. We describe Arbok-BC, a containerised vacuum unit that removes sulphur, water, paraffins and solid particles from heavy marine fuel ashore, at ambient temperature, and ARBOK-MarineSludge, an onboard vacuum module that takes over the scrubber wash water. Sulphur in the cleaned fuel falls to single digits or tens of ppm. Treatment costs 10–22 USD per t of fuel net of by-product income, against 100–150 USD for refinery hydrotreating. Both technologies are at TRL 7.