(Reuters) - Tougher rules on sulfur emissions from ships will come into effect next year in the biggest shake-up for the oil and shipping industries for decades.
From January 2020, United Nations shipping agency the International Maritime Organization (IMO) will ban ships from using fuels with a sulfur content above 0.5%, compared with 3.5% now.
The regulations are aimed at improving human health by reducing air pollution.
Only ships fitted with sulfur-cleaning devices known as scrubbers will be allowed to continue burning high-sulfur fuel. Ship owners can also opt for other sources of cleaner fuel such as liquefied natural gas (LNG).
Failure to comply with the global regulations will result in fines or vessels being detained and in some jurisdictions the risk of imprisonment, which could affect vital requirements such as insurance cover.
Enforcement will be policed by flag and port states rather than the IMO and industry officials are still unsure about whether there will be full compliance when it kicks in.
Refineries separately face significant costs to adapt to the new fuel specifications.
Oil majors including BP and Royal Dutch Shell have announced they are producing very low sulfur fuels that meet the 0.5% requirements.
While major fuel bunkering ports such as Singapore, Fujairah in the United Arab Emirates and Rotterdam in the Netherlands have compliant-fuel supplies, analysts and shipping firms are still unclear what will happen at smaller ports given the need for ships to plan their sailing routes.
It remains unclear what impact there will be with mixing very low sulfur fuels of 0.5% together, which at this stage have not been fully tested on ship engines. One of the risks is that the level of sediment created could damage engines at sea.
While guidance has been issued on avoiding mixing different fuel batches, the issue continues to raise worries especially after a major problems with bunker fuel contamination in 2018.
There is still a question over whether jurisdictions and ports could restrict the use of certain types of scrubbers due to uncertainty over the effects of the waste water that gets pumped into the sea.
Earlier this year ten environmental groups called on the IMO to impose an immediate ban on the use of scrubbers.
Users of the devices argue that there is no conclusive scientific research showing that discharges from open loop scrubbers - which wash out the sulfur - cause environmental harm and their use was safe. Analysts say there is still the possibility of tighter restrictions, which would add to the costs of those investing in them.
The IMO has encouraged further study into the impact of scrubbers on the environment.
Reporting by Jonathan Saul, Editing by