Ship shape: Clean future for shipping

Shipping is key to the smooth running of the global economy. With about 50,000 merchant ships trading across the seas, the shipping industry is responsible "for the carriage of around 90 percent of world trade," according to the International Chamber of Shipping.

However, the industry's environmental impact is not insignificant. In 2012, international shipping was responsible for 796 million tonnes of CO2 emissions – around 2.2 percent of global emissions – according to the International Maritime Organization.

"Shipping impacts the world in many positive ways by enabling trade around the world," Mads Stensen, global sustainability manager at Maersk, told CNBC's Sustainable Energy.

"But despite… all the positive impacts, you also have negative impacts, especially environmental impacts," he added.

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With this in mind, manufacturers are looking at ways to mitigate the environmental impact of big ships -- as well as make savings.

One idea being looked at is adding a "scrubber" – an exhaust gas cleaning system – to the huge engines that power the vessels. "The system can remove, for example, sulphur emissions from the exhaust gas," Stensen said.

Stensen went on to add that Maersk was looking to modify and update its fleet to help boost its efficiency and sustainability.

These include upgrading engines, propellers that are more fuel efficient, and increasing the capacity of the vessel so more containers can be carried on board.

At Maersk, cutting edge technology is also helping the company to improve efficiency. Its Eco Voyage Tracker (EVT) was developed internally and allows the company to monitor its fleet across the world's oceans at all times.

"It's also a tool that helps the vessel plan the most optimal voyage… that's the 'eco-voyage' part of it," Niels Bruus, head of fleet performance at Maersk, said.

Other innovations taking place in the industry are looking to the past for inspiration. Last year CNBC spoke to SkySails, a German company that says it has developed a "kite wind propulsion" system for large cargo ships.

According to SkySails, one kilowatt hour of their wind power costs only six cents for ships to use, "about half as much as one kilowatt hour from the main engine."

Back at Maersk, they are hoping their Triple E Class of ships will help to reduce emissions and improve sustainability. Sailing between Asia and Europe, Maersk say that the vessels – measuring 400 metres in length – will help to reduce CO2 emissions by 35 percent per container moved, compared to the industry average on the Asia-Europe trade.

This will be achieved thanks to a new hull design, an energy efficient engine, and a waste heat recovery system.

Ensuring that ships are clean as well as big is set to become increasingly important in the next few years.

"It is easy to forget but I think as the world economy globalizes shipping is going to increase in importance," Arpad Horvath, professor of civil and environmental engineering at the University of California Berkeley, told CNBC.

"Already about half of the world's GDP is generated in coastal areas where ships are obviously visible," he added.

"Ninety percent of international trade goes on ships. If anything, shipping is going to increase in importance in the future."