Shipping faces increasingly strict air emission rules. From sulfur limits to carbon intensity, here is what ship operators need to know.
MARPOL Annex VI regulates air pollution from ships, and its requirements have become increasingly stringent over the past decade. For ship operators, compliance is not optional — it is a condition of entering port and trading internationally.
Sulfur Limits: The 2020 Revolution
The global sulfur limit for fuel oil was reduced from 3.5% to 0.50% in 2020, one of the most significant regulatory changes in shipping history. This required widespread adoption of low-sulfur fuels, exhaust gas cleaning systems (scrubbers), or alternative fuels like LNG.
EEXI and CII: The Carbon Framework
In 2023, two new frameworks took effect:
- EEXI (Energy Efficiency Existing Ship Index) — a one-time technical efficiency assessment for existing ships
- CII (Carbon Intensity Indicator) — an annual operational efficiency rating from A to E
Ships receiving a D rating for three consecutive years or an E rating must develop a corrective action plan. This creates ongoing pressure to improve operational efficiency.
Practical Compliance Strategies
Operators can reduce emissions through several approaches:
- Slow steaming — reducing speed is the single most effective way to cut fuel consumption
- Hull cleaning — removing biofouling reduces drag and fuel use
- Route optimization — using weather routing to find the most efficient path
- Energy-saving devices — air lubrication, wind-assisted propulsion, and waste heat recovery
- Alternative fuels — LNG, biofuels, and eventually ammonia and hydrogen
Looking Ahead
The IMO's revised greenhouse gas strategy aims for net-zero emissions from international shipping by or around 2050. This will drive continued regulatory tightening and technological innovation. The operators who invest in efficiency now will be best positioned for the transition ahead.
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