In 1938, 18-year-old Eric Newby, later a famous travel writer, left home and sailed on the last voyage of the four-masted barque Moshulu, hauling grain from Australia to Britain. It was to be the final year that sailing ships seriously played a part in world cargo transport. Until now, perhaps.
The agricultural trade giant Cargill has just finished retrofitting a dry bulk carrier, the TR Lady, with rotor sails. The same company has also deployed wing sails on another ship, the Pyxis Ocean, which recently set sail from China for Brazil. The wind could now blow modern maritime trade into a lower-carbon future.
International marine traffic accounts for nearly 3 percent of global greenhouse gas emissions, more than direct emission from much-criticized aviation. Air travel is sometimes, wrongly, regarded as a luxury, but ships carry 90 percent of world goods and commodities and have no viable alternatives on most routes. Without action, the expansion of world trade means shipping emissions could roughly double by 2050.
The International Maritime Organization decided in July that international shipping should reduce its carbon dioxide emissions intensity (that is, per metric ton of cargo carried per nautical mile) at least 40 percent by 2030, and reach net-zero emissions around 2050. Large ships have a lifetime of 20 to 30 years, so vessels constructed over the next few years will still be plying the seas by the net-zero date.
There are various ways to improve performance: in the short term, boosting efficiency by better ship design and engines, drag-reducing agents, and slower steaming, which reduces fuel consumption. The main long-term decarbonization concept is to replace today’s predominant heavy fuel oil and marine diesel with low-carbon fuels: batteries over short distances, biofuels, ammonia, “green” methanol or others for longer voyages.
But these are expensive today, not readily available at all ports, and shipping will compete for a likely limited pool of fuels with aviation. On-board carbon capture and storage is feasible but would raise costs and take up cargo space. Marine haulage is a highly competitive industry, and fuel represents 50 percent to 60 percent of total operating costs.
Re-enter the sail. This does not resemble the elegant but complex, labor-intensive array of mainsail, topsail, sheets, jib and skysail that adorn classic ships such as the Cutty Sark, HMS Surprise or the lateen sails of Oman’s historic Fateh Al Khair dhow. Modern wind assistance has various forms.
The TR Lady has three rotor sails, which look like large chimneys, built by Anemoi Marine Technologies, a UK-based company. They spin in the wind, exploiting the Magnus effect which creates a pressure differential. This helps drive the ship, saving 10 percent of its fuel consumption. They can fold to pass under bridges or avoid damage in storms, or move from side to side on rails so as not to obstruct unloading.
The Pyxis Ocean has been fitted with large solid wings that could reduce emissions by 30 percent. Designed by UK-based BAR Technologies, they draw on technology used in America’s Cup racing yachts. Airseas, founded by former Airbus engineers, and based in Nantes, France, has a different system, a large parafoil kite that deploys on cables ahead of the vessel. Other options include inflatable wing sails, or an automated modern version of traditional sails.
As well as Cargill, shipping giants such as Maersk Tankers and Mitsui O.S.K. Lines are looking seriously at wind assistance. In 2019, they created Njord, a partnership for shipping decarbonization that offers several technologies, including wind power.
Rotors and rigid sails can cost $1 million to $1.5 million each and a ship may need three or more. That is a substantial addition to a bulk carrier costing $25 million to $40 million to build, but relatively less for a $120 million to $130 million very large crude carrier. The payout time may be seven to eight years.
But the economics look better using more expensive “green” fuels, or if a maritime carbon price is imposed. Maersk has proposed a stiff tax of $150 per metric ton of carbon dioxide emissions, while from 2024, ships will fall under Europe’s emissions trading system, currently around 88 euros (US$95) per metric ton. This will increase the effective cost of bunker fuel by almost half, cutting the sails’ payback period to about five years.
Maritime is a conservative business, though, and financing innovative vessels is difficult. Only in the past couple of years has the combination of higher bunker fuel prices and decarbonization pressures imparted momentum to modern sails.
The International Energy Agency’s roadmap for net-zero shipping saw wind assistance contributing about 15 percent of the required reductions. Today’s satellite-aided weather-forecasting would allow ships to adjust routes to take advantage of the winds. They would still run primarily with engines so areas of low wind would not halt them. The combination of improved and purpose-built sails, route optimization and other efficiency measures delivers bigger combined savings.
As historian Felipe Fernandez-Armesto’s book on exploration, “Pathfinders,” explains, places that look easy to reach on a modern chart may not have been in the past age of sail. Winds don’t blow and currents don’t flow conveniently on the shortest route between ports. A future of hybrid sails and engines wouldn’t quite have that problem, but still, ships’ courses may be longer and more circuitous to take advantage of strong winds.
Harbors that were hitherto backwaters might find themselves literally on the map. And a new twist on an ancient technology could help clean up one of the toughest polluting sectors.
Robin M. Mills is CEO of Qamar Energy, and author of “The Myth of the Oil Crisis.”