Improving energy efficiency has paid off for shipping giant Maersk Line, which has reduced harmful air emissions while growing their business according to a report released on Monday by the company.

Maersk Line accomplished this mainly through an overhaul of its global network of shipping routes last year which helped lower fuel costs and cut carbon dioxide emissions.

The Danish company also credits the four Triple-E ships introduced last year which are designed to be energy efficient and environmentally-friendly for improving energy efficiency, and will add 16 more to its fleet by 2015.

Maersk Line's ships used 1.2 million tonnes of fuel less last year than the year before, a move that has saved US$764 million - helping the company deliver a US$1.5 billion profit in 2013.

The world's largest container shipping line also grew their business by 4.1 per cent last year compared to 2012 and cut its carbon dioxide emissions by 3.8 million tonnes over that same period.

Maersk Line reduced also reduced its sulphur emissions by 67,000 tonnes - 12 per cent - last year compared to 2012, mainly through switching to low sulphur fuels, such as diesel.

This method has allowed Maersk Line to reduce its sulphur emissions in Singapore by 50 per cent last year compared to 2012.

This has resulted in 478 tonnes of sulphur emissions saved, equal to around half of all sulphur emissions from vehicles in Singapore.

"We appreciate the Singapore Green Port Programme, and we think it can be made even better," said Mr Thomas Knudsen, Maersk Line's chief executive for the Asia-Pacific, " we believe regulation is an effective way to reduce air emissions."

The Green Port Programme is a scheme by the Maritime Port Authority which allows ships that burn cleaner fuels at Singapore's port to pay less in port dues to incentivise the switch to cleaner fuels in shipping.