After a commitment last month to cut greenhouse gas emissions from shipping by at least 50% by 2050, the race is on to find new technologies that can green the 50,000-strong global shipping fleet. Wind power is one of the options being discussed.
International shipping accounts for more than 2% of global carbon dioxide emissions, roughly the same as aircraft. But the 2015 Paris agreement to fight climate change left control of the shipping industry’s emissions to the International Maritime Organisation.
While environment groups applauded the agreement to cut hard and deep by 2050, they pointed out that it falls far short what is technically achievable.
A report published just before the meeting by the International Transport Forum (ITF), a thinktank run by the Organisation for Economic Co-operation and Development (OECD), found that the industry could achieve up to 95% decarbonisation as early as 2035 using “maximum deployment of currently known technologies.”
The good news is that easy-to-do low-tech solutions can deliver a lot. Maersk, the world’s largest container shipping line, has already discovered it can cut fuel use 30% simply by steaming more slowly.
Because of the wide availability of cheap (and often dirty) fuel, shipping has traditionally been wasteful. Most merchant ships are made of heavy steel rather than lighter aluminium, and don’t bother with obvious energy-saving measures like low-friction hull coatings or recovering waste heat.
More slender ship designs alone could cut fuel use — and hence emissions — by 10-15% at slow speeds and up to 25% at high speeds, says the ITF. But replacing the existing fleet would take time. The average age of today’s shipping fleet is 25 years. Rules of energy efficiency for new ships introduced by the IMO in 2013 will only fully come into force from 2030, meaning that any switch to slender ships would not apply to most ships at sea until mid-century or beyond.
But much could be done more quickly by retrofitting existing ships with technology to cut their fuel use and hence emissions, according to the ITF. Here are just four:
Fitting ships’ bows with a bulbous extension below the water line reduces drag enough to cut emissions 2-7%;
A technique known as air lubrication, which pumps compressed air below the hull to create a carpet of bubbles, also reduces drag and can cut emissions by a further 3%;
Replacing one propeller with two rotating in opposite directions recovers slipstream energy and can make efficiency gains of 8-15%,
Cleaning the hull and painting it with a low-friction coating can deliver gains of up to 5%.