"2013 was a good year for Maersk Line - financially as well as in terms of our sustainability performance," said CEO Soren Skou. "Our fuel efficiency improvements helped cut CO2 as well as air pollutants like SOx and NOx.
"So even while our business grew, we were able to reduce our environmental impact in absolute terms," he said.
In 2013, the shipping line took delivery of the first four of 20 Triple-E 18,000-TEU vessels that will set a new standard for energy efficiency.
However, the main driver for the strong CO2 performance was the major overhaul of its carrier network.
The company said that one of the challenges outlined in the report is the tightening regulation of sulphur emissions (SOx) that will require ships sailing in emission control areas to switch to cleaner and thus more expensive fuels from January 2015.
"Air emissions are a serious issue in shipping and we support the upcoming regulation. We are, however, concerned about the level of enforcement in Europe.
"The new regulation will be costly and without proper enforcement, some might be tempted to cut corners. This will erode the environmental improvements and create a commercial disadvantage for those that follow the rules," said Maersk's head of sustainability Jacob Sterling.
Last year, customer demand for information on the company's sustainability performance was said to have really taken off.
"Large customers representing 19 per cent of our business have requested tailored sustainability information as part of their business relationship with us," said Mr Sterling.
"These customers have typically made promises to their stakeholders on sustainability. We are proud to move their goods with a lower environmental impact year by year, thereby helping them deliver on their sustainability promises."
In total, its customers saved 2.6 million tonnes of CO2 in 2013 by shipping their goods with the world's largest shipping line compared to an industry-average competitor.