A Singapore shipping firm performed on Monday what it called the world's first simultaneous refuelling of a container ship with bio-methanol while it was being loaded with cargo in the port.

Simultaneous loading and refuelling hastens a vessel's turnaround time, according to Shmuel Yoskovitz, chief executive of Singapore-based X-Press Feeders.

With extra time, the ship can sail at a slower pace, reducing fuel use and leading to lower costs and emissions, he added.

Global maritime transport accounts for 2.89 percent of total greenhouse gas emissions, data from the International Maritime Organisation shows. On a global scale, it is more polluting than air transport.

"This milestone represents a significant leap forward for X-Press Feeders and the global maritime industry," said Francis Goh, the firm's chief operating officer.

He told reporters that as far as they know this was the first such simultaneous port refuelling with green methanol.

Green methanol, or bio-methanol, is composed of waste carbon dioxide (CO2) and "green hydrogen", which is created by using renewable energy to split water molecules.

Compared to conventional marine fuels, green methanol has a lower carbon footprint, cutting emissions by up to 65 percent, according to X-Press Feeders.

Last year, a ship was refuelled with bio-methanol via another ship, but this was done offshore.

Singapore's Maritime and Port Authority, which supported Monday's refuelling at the Tuas Port, signalled a readiness to offer methanol bunkering on a commercial scale.

The city-state operates the world's second-biggest port and is a major bunkering hub.

Last year, in a bid to meet greenhouse gas reduction targets set by the European Union, Danish shipping giant Maersk launched the first container ship running on bio-methanol.

X-Press Feeders' ship is the first vessel made in China that can run on both conventional fuel and green methanol.

The company said it will add 14 such dual-fuel vessels to its fleet over this year and next.