Big Ships Account for 80 Percent of Shipping's CO2

At Nor-Shipping 2017, researchers with DNV GL released a study that points to the difficulty of reducing the industry’s CO2 output below current levels. The problem is structural: big cargo vessels emit 80 percent of shipping's greenhouse gases, but they're also the industry's most efficient ships, and squeezing out additional improvements may be a challenge.

Just 35 percent of the fleet – mostly large bulkers, tankers and container ships – is responsible for 80 percent of shipping’s fuel consumption, according to Christos Chryssakis, DNV GL's group leader for greener shipping. Unfortunately, these are already the fleet's most efficient vessels per ton-mile. "This is a paradox, but if we want to reduce our greenhouse gas emissions, we actually have to improve the best performers," Chryssakis says.

Among other implications, his analysis suggests that low-emissions technologies that can realistically be used on big ships – LNG bunkering, advanced hull coatings, Flettner rotors, etc. – are the most important from a greenhouse gas perspective. In addition, the study points to the need for global rather than national regulation: small operators in territorial seas are not the main source of emissions. 

SOx and CO2 regulation are interrelated

Reducing carbon emissions from the biggest ships may be harder if restrictions on SOx emissions push shipowners to install exhaust scrubbers. Scrubbers allow large ships to burn high sulfur HFO while maintaining compliance with SOx requirements, but they reduce fuel efficiency and increase CO2 emissions by a small percentage. Leading class societies have discussed this issue for some time in the context of cost-benefit analysis; one of them advises the shipowner to consider the potential "cost of the additional fuel consumption to operate the scrubber system" when weighing SOx compliance options. The efficiency loss is small, but Chryssakis suggests that it may still have a noticeable impact on fleet CO2 output.

An LNG-fueled bulker

At the same press conference, DNV GL announced that they've created a new bulker design that could help with this specific problem. Their new "Green Corridor" concept vessel is an LNG-fueled Newcastlemax designed for runs from Australia to China. The vessel is based on a traditional bulker design and is conventional in appearance, but it can carry 6,000 cubic meters of LNG fuel beneath its decks.

The Australia-China route has some attractive attributes for LNG bunkering. Australia has a lot of LNG, and the rotation is regular and established, with predictable opportunities to bunker at set locations. Three Australian mine operators and an Australian LNG producer all have an interest in the project, along with shipowners MOL and U-Ming. This vessel may be built soon: no contract has been announced yet, but DNV GL suggests the design is "ready to serve as the outline specification for newbuilding orders already in 2017."