IN FEBRUARY 1925, a strange kind of ship put out from the wharves of Kiel, Germany, onto the cold Baltic Sea. It sliced through the water, with two towers resembling giant smokestacks rising from its deck. But according to accounts from the time, no smoke was to be seen and no engine noise could be heard.
This could have been the start of a new age of shipping. Created by German engineer Anton Flettner, those towers were clever devices that harnessed the power of the wind better than any piece of cloth. They worked well – but alas, they didn’t catch on. The designs languished in dusty bottom drawers for nearly a century, as ships relied instead on cheap fossil fuels to ply the oceans.
That reliance on fossil fuels has become a huge problem. Shipping is a vast industry that underpins the global economy, helping to deliver all manner of goods, from food to fridges to fidget spinners. Yet it is a horror to the environment, with vessels burning dirty fuel and spewing vast amounts of greenhouse gases.
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Now, shipping is beginning to grapple with its climate conscience and serious efforts are under way to cut those emissions. Inventions like Flettner’s could be part of the solution, along with sleeker vessels, smarter navigation and greener fuels. There are choppy waters ahead, to be sure, but the technology we need to make our sea transport environmentally shipshape is on the horizon. “We’re steering towards zero-emission transport,” says Héléne Smidt at the Royal Belgian Shipowners’ Association.
“110,700 Number of ships weighing more than 100 gross tonnes”
Shipping has come a long way since 1925, not least thanks to the invention of the shipping container in the middle of the 20th century. This standardised and industrialised ocean transport, helping it grow to epic proportions. Add in oil tankers, tugs, ferries, bulk carriers that bear minerals and ores – and all the rest of the world’s vessels – and there are more than 110,000 large ships on the oceans today. Some have grown to colossal sizes. The Ever Given, the container ship that blocked the Suez Canal in March, is longer than the Eiffel Tower is tall – and it isn’t even the biggest ship out there.
All those ships collectively , with container ship traffic the worst offender (see “Dirty ships”). Together, the industry is responsible for almost 3 per cent of global emissions, roughly the same as aviation. Shipping is so dirty in part because it relies on bunker oil, a fossil fuel with the consistency of tar, rife with sulphur and nitrogen compounds that turn into pollutants when burned. “It’s the sludge left at the bottom of the barrel after you’ve refined everything else,” says Gavin Allwright, head of the International Windship Association. “It’s toxic waste.”
Blame game
Until recently, the problem of shipping emissions had been shoved aside. One reason for this is disagreement over who is responsible for them: the country that sold the fuel, the country where the ship is registered or the country shipping or receiving the goods.
That neglect is starting to lift. In 2018, the UN’s International Maritime Organization (IMO), which can set mandatory rules for the shipping industry, put in place the goal of reducing every ship’s carbon intensity – that is, the emissions per weight per distance travelled – by at least 40 per cent compared with 2008 levels by 2030. In June 2021, it introduced new rules for compliance with specific measures of efficiency and carbon intensity that ships will need to meet by 2023.
“553 Number of ships using sources of power other than bunker oil, mostly batteries or liquid natural gas”
The trouble is that ocean traffic is expected to keep going up. This means that even a significant lowering of all ships’ carbon emissions could be overshadowed by the sheer number of new vessels belching carbon as they make more trips. For this reason, the IMO has also set the goal of cutting total greenhouse gas emissions from the shipping industry by 50 per cent by 2050 – though the mechanisms to make this happen are still being thrashed out. These targets could soon get even more stringent: the emissions rules are due for revision in 2023 and Roel Hoenders, head of the IMO’s air pollution and energy efficiency efforts, says this will “very likely contain more ambitious and more far-reaching goals”
One way to meet the immediate goals would be to stop shipping so much stuff around the planet. Some forecasts do anticipate the size of the global maritime fleet levelling off by 2050, mainly thanks to a reduction in tankers, even as shipping container numbers continue to rise. But for now, traffic is soaring. While there was a downward blip during the early months of the pandemic, it has rebounded in force. A 2019 analysis led by Anthony Sardain, then at McGill University in Canada, projected that, by 2050, 2 and 12 times compared with 2014 levels.
“Chugging along at half speed provides a hefty two-thirds reduction in fuel requirements”
The good news is that the IMO’s 2030 target can be largely achieved by ramping up relatively simple efficiency measures that are already under way. These include things like giving ships a “nose job” to make the prow more hydrodynamic, applying special low-friction coatings or blowing bubbles under the hull to lubricate passage. It could also include simply packing more containers onto ships, travelling only when full and rerouting to avoid bad weather. Perhaps the most important trick is the simplest of all: chugging along at half speed provides a hefty two-thirds reduction in fuel requirements. Maersk, the world’s largest shipping container operator, with more than 700 vessels, says it has already sliced its carbon intensity by about 46 per cent since 2008 using such measures. Many other large shipping firms are taking the same tack: the IMO estimates that, by 2018, the industry’s average carbon intensity had already been cut by at least 20 per cent.
The 2050 target of reducing total emissions from shipping by 50 per cent will be much harder to hit. Given that maritime trade has already gone up more than a third since 2008, along with projected increases in ship traffic, this will require reducing the average ship’s carbon intensity by more than 80 per cent, says engineer . Achieving that will require both swapping bunker fuel for lower-carbon alternatives and figuring out ways to use a heck of a lot less of it (see “Every little helps”).
When it comes to low-carbon fuel, electric batteries and fuel cells will be part of the solution, creating peaceful rides without the smells and vibrations of a fuel-powered vessel. “You don’t actually feel that you’re on a ship,” says Hoenders. But these solutions take up a lot of space for the power they produce. “If we wanted to actually propel a container ship just with batteries, we’d have no room left for cargo,” says Lee Kindberg, Maersk’s head of environment and sustainability.
One of the few technologically mature alternative fuels that has the oomph for international shipping is liquefied natural gas or LNG. This burns cleaner than bunker fuel, producing about a quarter less carbon dioxide and has been touted as a bridge fuel to get the shipping industry to lower emissions. Its use went up by about 26 per cent between 2012 and 2018. The trouble is that LNG consists mainly of methane – an extremely potent, if short-lived greenhouse gas – which tends to leak out of pipes and engines. This may make using LNG entirely counterproductive.
Maersk is avoiding LNG because of precisely this problem, says Kindberg. Instead, it is replacing up to 30 per cent of some of its ships’ bunker fuel with biofuels made from used cooking fat. This cuts emissions from a small number of vessels, allowing the firm to charge a premium for zero-carbon shipping for a fraction of the cargo. Some other large shipping firms, such as Mediterranean Shipping Company, have taken similar action.
While the emissions savings are real, Smith says the cooking fat strategy is a “disingenuous quick fix”. This is because there just isn’t enough biofuel around for it to act as a large-scale solution. He gives Maersk more credit for commissioning eight new ships designed to run on green methanol, a carbon-based fuel similar to alcohol, which will be made in plants powered by clean electricity.
Fuel of the future?
In the longer term, maybe a decade from now, many shipping firms are betting on ammonia as the fuel of the future. Ammonia, composed of nitrogen and hydrogen atoms, produces no CO2 when burned. It is similar in that respect to hydrogen, which is often considered as a future green fuel. But ammonia has twice the energy per volume and can also be used in either a combustion engine or a fuel cell.
“Ammonia is very promising as a fuel for the bigger ships,” says Smidt. But there are still hurdles. Ammonia is toxic, so hauling it around can be dangerous. And, while it doesn’t produce CO2, burning it does generate nitrogen dioxide, which makes smog, and nitrous oxide, which is itself a potent greenhouse gas. Ships will need systems to limit or scrub those emissions.
The bigger difficulty is making enough ammonia in a green fashion. Right now, the world produces about 150 million tonnes of the stuff a year, mainly for agricultural fertiliser, through an energy-hungry process that has a gigantic carbon footprint. “We will need 400 to 500 million tonnes of ammonia to feed shipping,” says Smith – and it needs to be made without using fossil fuels for energy. This is a huge – but achievable – task, says Smith. For now, however, there are only a handful of such projects afoot.
According to a 2021 report by consultancy DNV, only 0.5 per cent of the global shipping fleet is currently running on alternative sources of power, mostly batteries and LNG. Things are changing though: 12 per cent of new ships on order have alternative fuel systems, which is double the percentage from the firm’s 2019 assessment. Alternative fuels will need to feed at least 60 per cent of the global fleet by 2050.
Moving that fast will require some serious incentives, says Smith. Hoenders revealed to Â鶹´«Ă˝ that the IMO is working on measures now. “It is very likely there that the IMO will put in place a market-based measure in the coming years,” he says, perhaps a cap-and-trade system. “We need a carbon price for shipping,” he says.
At COP26, the climate conference recently held in Glasgow, UK, 22 countries signed the “Clydebank declaration” pledging to develop “green shipping corridors” between their ports, supplying the technology and expertise for ships on these routes to run entirely on green fuels. The first such corridors could be up and running by the end of the decade.
Because swapping fuels isn’t exactly a quick fix, plenty of effort is also focused on reducing fuel use – and that includes returning to some of the old ways of crossing the seas. “We should be doing everything we can with wind,” says Smith.
Take those strange towers that appeared on the ship back in 1925. They are known as Flettner rotors. They work using the same principle that makes a spinning baseball curve in flight: the wind moves relatively more quickly on one side of a spinning object than the other, creating a pressure difference and a resulting force. In this case, it isn’t a ball but a tall, rigid pole, spun on its long axis by a motor. “They’re completely bizarre-looking things, but it works,” says Allwright.
Finnish company Norsepower has done about 10 Flettner rotor installations in the past decade, including on a tanker called the Maersk Pelican. An independent assessment showed that . Other studies predict the devices could make savings of closer to 20 per cent. Earlier this year, five rotors were installed on the Sea Zhoushan, a gigantic ore carrier. Other more exotic incarnations of sails are being developed too (see “Water wings“).
“If we wanted to propel a ship with just batteries, we’d have no room left for cargo”
Of course, the wind isn’t always up, or blowing in the right direction. But improved weather forecasts and route-plotting software have eased those troubles, says Allwright. And other more innovative strategies could make use of the wind no matter what. The Lines is aiming to create a tanker that would produce hydrogen from wind-made electricity while moving: the tanker could set out empty and create its own environmentally friendly cargo en route, in a win-win for low-carbon fuels. For now, though, only 15 large international ships use wind assistance of any kind, says Allwright – although he expects that to ramp up quickly.
All such efforts will be needed to hit the IMO’s target of 50 per cent emissions reductions, says Smith. But that is a low bar, considering the global goal of net-zero emissions by 2050. For shipping too, he says: “It should be zero.” The day might come sooner than we think when there are more ships moving silently across the waves, like that mysterious craft that set sail on the Baltic all those years ago.
Water wings
French explorer and ocean researcher Jacques Cousteau was taken with the idea of using tall poles to harness the wind and power ships (see main story). In the 1980s, he set out to design his own. He ended up with a device he called the turbosail. It is essentially a hollow aircraft wing erected vertically on the deck of a ship, with flaps that can open and close. A motorised fan sucks air out from inside the turbosail, and air flows over its surface, creating thrust in a similar way to how a wing produces lift on an aeroplane.
Cousteau’s idea never went mainstream. But now Econowind, a company based in the Netherlands, is pursuing the concept with its modern turbosails called Ventifoils. The company has done two installations since launching two years ago, and has a portable container that it rents out, which can be installed on a container ship to give it instant, pop-up Ventifoils. Econowind says this produced between 7 and 11 per cent fuel savings on a trial run in 2019.
Innovators are also playing with hulls that are themselves shaped like aeroplane wings, and with souped-up versions of simple technologies like kites. This year, Airseas, a spin-off from engineering company Airbus, is installing a 500-square-metre SeaWing kite on a cargo ferry called the Ville de Bordeaux. The company predicts it will lead to a 20 per cent improvement in fuel economy, with an AI-powered system helping steer the kite to harness every puff of wind.
