"The next important target is fast approaching, when carrying non-compliant fuel oil on board ships becomes prohibited on March 1, 2020," Lim said.

While in the port, vessels fitted with hybrid type of scrubbers should switch to the closed-loop mode of operations, it said.

As a result of the full 13% VAT rebate, the Yuan 1,218/mt ($176/mt) consumption tax on fuel oil will also be refundable.

The notice pertains to Bahraini and foreign flagged vessels calling at Bahrain's ports or operating in Bahraini waters.

Full decarbonization by 2050 will require further investments of some $400 billion over 20 years.

"The entire blending business will be supervised by customs officials, so the quality of the newly blended crudes can be guaranteed," an official said.

Scaling up will be the biggest driver of cost reduction, the council said.

A similar permit is already in place for LNG, it said.