On 1 January 2020, a new limit on the sulphur content in the fuel oil used on board ships came into force, marking a significant milestone to improve air quality, preserve the environment and protect human health.
Known as “IMO 2020”, the rule limits the sulphur in the fuel oil used on board ships operating outside designated emission control areas to 0.50% m/m (mass by mass) - a significant reduction from the previous limit of 3.5%. Within specific designated emission control areas the limits were already stricter (0.10%). This new limit was made compulsory following an amendment to Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL).
The resulting reduction in sulphur oxide (SOx) emissions from ships is having major health and environmental benefits for the world, particularly for populations living close to ports and coasts. Sulphur oxides are harmful to human health, causing respiratory, cardiovascular and lung disease. Once released in the atmosphere, SOx  can lead to acid rain, which impacts crops, forests and aquatic species and contributes to the acidification of the oceans.
Before the entry into force of the new limit, most ships were using heavy fuel oil. Derived as a residue from crude oil distillation, heavy fuel oil had a much higher sulphur content which, following combustion in the engine, ended up in ships’ emissions. Now, the vast majority of ships are using very low sulphur fuel oil (VLSFO) to comply with the new limit, and no safety issues have to date been reported to IMO.