The Future of The Cargo Ship Looks Much Like Its Past
This edition covers some issues around the growing current of thought that sailing cargo ships could help decarbonize the maritime transport sector.
It all started with a vision. As I was standing on the deck, feeling the fresh breeze pierce through my light sweater, I looked up to see the immense wing-like sail that was towering above me. It felt like I was flying above the water. I looked towards the horizon and wondered why doesn’t every other vessel around me use sails anymore? Why have we become so addicted to burning dirty fuels to power ever-increasing metal mammoths while ignoring the alternative of harnessing nature’s forces?
Almost every story that talks about using wind power for cargo ships follows this romantic train of thought. Just have a look at these passages from the New Yorker:
“…a German sea captain who had worked with oil companies, bought the Avontuur and made it the flagship of a company called Timbercoast. His mission was to eliminate pollution caused by cargo shipping […] Bockermann’s company is one of several founded on a provocative idea: What if shipping’s history could inspire its future? For centuries, the cargo industry ran on clean wind power—and it could again. As the climate crisis has escalated, and the pandemic has exposed weaknesses in global supply chains, the movement to decarbonize shipping has spread.”
Even marketing videos for sailing technology play uplifting soundtracks which suggest the emergence of a foundational transformation. There is, however, a difference which is often overlooked between sailing on a yacht and sailing on a tanker in as much as there is a difference between riding a bicycle and driving a truck. The activity itself is rarely the differentiating factor – both a sailboat and a cargo ship sail on water. Rather, it is the broader context in which cargo ships operate, meaning supply chains - which makes wind-powered maritime transport largely unfeasible at scale.
Options to Decarbonize Shipping
Shipping accounts for around 3% of the world’s carbon emissions. Naturally, this means that the sector should take steps to decarbonize and thus minimize its emissions footprint. Alternative fuels -methanol, ammonia, biofuels, liquefied natural gas (LNG) to some extent - are one of the main decarbonization pathways for shipping. Another proposed pathway harnessing wind power by using sails or wing-like structures on vessels. Interestingly, various wind power methods (some examples below) have been proposed to either improve fuel efficiency or completely replace fuel-powered cargo vessels.
Although both pathways – alternative fuels and wind power - show promising potential, it’s important to realize the scale at which shipping decarbonization should happen. In 2020, cargo ships used 175 million tonnes of heavy fuel oil.
Alternative Fuels for Shipping: A Scale Problem
To replace all heavy fuel oil consumption with methanol alone, would require roughly 336 million tonnes of methanol (methanol has a density of 793 kg/m3 as opposed to heavy fuel oil 993 kg/m3 and an energy density of 15.6 GJ/m3 as opposed to heavy fuel oil 38.9 GJ/m3). In 2021, the global methanol production capacity was 160 million tonnes. Although this is projected to grow by 80% by 2030 (which is quite a bit considering that 2030 is only 6 and a half years away), the increased capacity would still fall short of satisfying shipping’s demand for methanol, before accounting for other methanol uses. Adding to this issue, much of the world’s methanol is produced from fossil fuels.
An estimation of ammonia as sole replacement for heavy fuel oil yields similar figures (roughly 400 million tonnes versus an existing production capacity of 230 million tonnes and a planned capacity increase to 290 million tonnes by 2030). Not to mention that ammonia is a widely used fertilizer which is still needed for agriculture and is another product which is mostly produced from natural gas.
Given that individual alternative fuels are unlikely to be produced in sufficient quantities to satisfy shipping demand, a mix of fuels is likely the answer (hopefully, at best) in the decarbonization using alternative fuels scenario. We’ll leave the questions around how alternative fuels’ production capacity can increase in a world where energy is becoming scarce for another upcoming substack. In the meantime, let’s look at the other decarbonisation option.
Wind Powered Cargo Ships
I am likely not the first nor the last to observe this alternative fuel capacity shortfall. It is understandable why the idea of using wind power to decarbonize shipping partially or fully may be rather attractive. In fairness, the idea does have its merits. Wind has powered shipping for a fair bit of human history and designs for cargo ships up to 15,000 deadweight tonnes (DWT) powered solely by wind are already under construction. More futuristic looking concepts like Oceanbird’s wingsail/sailwing are making waves. Oceanbird’s wing estimates a 90% emissions reduction on the ships using its technology – mainly car carriers. Some ship designers have taken things a step further, creating inflatable wing sails (see below) that can be mounted on cargo ships. Presumably this helps reduce the technology’s costs. Despite its merits, sailing has its downsides, some more obvious than others.
If you’re anything like me, the first major disadvantage you would have noticed is the wings’/sails’ size. Even for a relatively small ship carrying 15,000 DWT, the sails’ mast (central pilon) must be around 75 metres high, and the sail should be roughly 8,500 m2. That’s rather large for a relatively small vessel. A 75 metre or taller mast means that ships wouldn’t be able to sail under most bridges. Engineers have figured this one out by creating telescopic or foldable masts which allow both transit under bridges as well as loading and unloading space in ports. Seems like the biggest engineering challenges are behind us. As in most cases, although most effort and attention is poured on technical challenges, these are not generally the insurmountable issues. This is also the case for sailing cargo ships.
The Straw That Breaks the Camel’s Back, Uncertainty
The major challenge for sail cargo ships is uncertainty. Wind isn’t constant nor always blowing from the right direction. Hence, there’s less certainty around wind powered ships’ speed. The same New Yorker article describes the challenges of relying solely on wind power in detail:
“In the Gulf of Mexico, they rediscovered the difficult realities of wind-powered transport. “We were going around in circles, taking the sails down and up again because of the squalls,” De Beukelaer told me. The ship zigzagged for weeks and supplies dwindled. After the fruits and vegetables were gone, the crew ate short rations. The cook worried that they’d run out of gas for the stove.”
The days in which ships carried mainly high-value luxury items – expensive surely but not necessarily essential for everyday life – have passed. Cargo ships nowadays transport anything from petroleum products to ping-pong balls, from timber logs to iPhones and semiconductor chips. Many of these products are either critical for everyday life or are inputs into global supply chains, many of them operating in a just-in-time framework. In either case, sailing time uncertainty is a significant problem, maybe even the straw that breaks the camel’s back for wind propulsion.
Take for instance Australia’s oil supply. In 2021, Australia consumed around 947,000 barrels of oil per day. That’s about one very large crude carrier (VLCC) worth every 2 days. Australia’s strategic reserves fluctuate. They should be around 90 days’ worth but are generally less. In February 2020, Australia’s onshore strategic oil reserve was at 56 days. What this means is that the buffer, the risk tolerance of oil supply chains, is relatively low. If too wind powered crude carriers ‘zigzagged for weeks’ because of poor wind conditions the likelihood of oil or fuel shortages increases dramatically as does the difficulty of rebuilding the buffer, once it’s been used up.
Supply chains’ tolerance for uncertainty is extremely limited. There’s no better example of the impact of uncertainty on supply chains than the Ever Given obstruction of the Suez Canal. As more and more news of the Suez obstruction highlighted the uncertainty of the refloating operation, some estimating days others estimating weeks or months, cargo owners and supply chain managers were faced with a difficult choice: wait, go around the Cape of Good Hope or, where possible air freight cargo. Each of these decisions had major cost and emissions consequences. Waiting was clearly a gamble, going around the Cape of Good Hope would add 9 days to ship travelling from Asia to Europe, approximately US$ 1.5 million in fuel costs alone and emit an additional 7,500 tonnes of CO2-e. Air freighting cargo, which is generally expensive became even more expensive and capacity tightened. From an emissions perspective, air freight is about 70 times more impacting than sea transport.
Ultimately, the Suez obstruction was cleared in 7 days, but by that time ships were re-routed, and cargo was air freighted. Maersk alone re-routed 15 vessels, as did MSC, two of the largest container shipping companies in the world. Air freight capacity was sold out for months. The uncertainty of the obstruction duration was enough to force these decisions. Neither costs nor emissions considerations made a significant difference when it came down to supermarkets, factories or shops needing supplies. It seemed climate change mattered, but not as much as the supply chain. Now imagine the impact that 3 days of unfavorable winds may have on an all-wind powered fleet. How quickly will the air freighters booked in as a response to uncertainty offset all the emissions savings of sailing cargo ships?
Cargo Shipping in an Interconnected World
In the rush to decarbonize and ‘tackle climate change’ and ‘save the planet’ we forget that everything is interconnected. Shipping doesn’t operate for its own sake. Ships operate in and for supply chains. The supply chains are built around the idea of logistics predictability and control. Just-in-time (JIT) isn’t just a marketing acronym, it is a manufacturing philosophy which entails maintaining limited inventory and warehousing capacity. Logistics uncertainty, whether land, air, or maritime, doesn’t really fit well in this situation.
Whether the cargo ships of the future will be wind assisted or wind powered makes little difference. Wind assisted ships will still rely on some form of liquid fuels, ideally alternative fuels available in sufficient quantities. Whatever fuel efficiency improvement wind assisted propulsion may bring, is is unlikely to be enough to satisfy decarbonization proponents. Shipping will always remain ‘dirty’ as long as it burns fossil fuels, even if it is the most fuel-efficient transport mode by tonne-km. Transitioning to wind propulsion ships will likely make shipping a transport mode unfit for purpose in supply chain. Global supply chains may well shrink or may just shift to other transport modes, of course more emissions intensive. In this case, the future of the cargo ships really does look very much like its past.