Background
The International Maritime Organization (IMO) adopted the 0.50% global sulphur cap through amendments to MARPOL Annex VI, taking effect on 1 January 2020. Prior to that date, most deep-sea vessels burned heavy fuel oil with sulphur content up to 3.50%. Inside pre-existing Emission Control Areas (the Baltic, North Sea, North American and US Caribbean ECAs), the limit was already 0.10%. The 2020 global cap extended stringent sulphur control to the world's open oceans for the first time.
Compliance options
Vessels have three compliance pathways: switch to a compliant fuel (VLSFO or LSMGO), install exhaust gas cleaning systems (scrubbers) that remove sulphur from exhaust allowing continued HSFO use, or switch to an alternative low-sulphur fuel such as LNG. Each has tradeoffs. Fuel switch requires no capital investment but means higher ongoing fuel cost. Scrubbers require capital expenditure in the single-digit millions per vessel but allow continuing use of cheaper HSFO. Alternative fuels require purpose-built or heavily modified vessels.
Market response
The refining industry invested significantly ahead of 2020 to produce 0.50%-compliant residual fuel blends (VLSFO). Early fears of global VLSFO shortage did not materialise, but early VLSFO had variable quality: compatibility problems between stems from different suppliers, elevated cat fines in some blends, and pour-point issues in cold climates. Quality has generally improved but blend variability remains.
Scrubber economics
The HSFO-VLSFO price spread is the primary determinant of scrubber profitability. The spread has varied — wider spreads favour scrubbers, narrower spreads reduce their advantage. For very large, high-consumption vessels, scrubbers often remain economic. For smaller tonnage, the economics are tighter.
Enforcement
Compliance is enforced by flag states, port state control (PSC), and through bunker sampling. The Bunker Delivery Note (BDN) certifies delivered fuel sulphur content; vessel's fuel oil sample retention is mandatory. PSC inspections commonly include fuel sulphur verification. Non-compliance attracts fines, detention, and reputational consequences.
Ongoing implications
IMO 2020 was the single largest change to the marine fuel market since the IFO grade standardisation of the 1980s. It catalysed interest in alternative fuels, fundamentally changed refinery economics, and established the pattern of progressively tighter environmental regulation. IMO's GHG strategy — targeting net-zero international shipping GHG emissions by or around 2050 — builds directly on the 2020 precedent.
Frequently Asked Questions
Do I still need to carry a BDN for fuel sulphur verification?
Yes. BDN requirements under MARPOL Annex VI have not been relaxed. You should retain BDNs for three years and sealed fuel samples for at least 12 months.
What happens if my bunker is delivered over 0.50% sulphur?
This is a serious matter. Document via bunker survey, notify the supplier in writing, retain samples, and secure independent lab testing. The commercial dispute is between vessel and supplier; regulatory exposure is to the vessel unless exoneration is formally established.
Can I rely on 'flexibility' if my VLSFO tests at, say, 0.52%?
Practically, minor exceedances may not trigger enforcement action, but regulators have not provided formal tolerance. Treat the 0.50% limit as a hard cap. If the BDN says 0.48% but the onboard sample tests at 0.52%, that is a supplier quality dispute — take action.
Are scrubbers still a good investment in 2026?
Depends on vessel size, consumption, remaining useful life, and financing. For large, high-consumption vessels with years of trading life remaining, scrubbers are often still economic. For older or smaller vessels, the decision is tighter. Each case needs its own financial modelling.