Along a stretch of river in northern Belgium, a small ferry is running on a fuel that many hope could hold the key to decarbonising ships everywhere.

The fuel being tested on Hydroville, a 16-passenger shuttle moving between Kruibeke and Antwerp, is hydrogen. Hydroville launched three years ago as the world’s first hydrogen-powered passenger vessel. Its hybrid engine allows it to run on both hydrogen and diesel.

“We decided for ourselves, look, we have to start with it today, even though there is no demand yet,” says Roy Campe, managing director at CMB.Tech, the R&D branch of CMB, Hydroville’s owner. “We have to start today to make certain that within 10 years we can already start producing all our ships on a low-emission level. It’s not a light switch that you just flip over.”

CMB is already building several other hydrogen-powered boats, including a larger, 80-person ferry in Japan set for launch in early 2021.  

The small boat sector is a great “proving ground” to scale up clean tech solutions for large merchant vessels, according to Diane Gilpin, founder of the Smart Green Shipping Alliance. Ships currently emit 3% of all greenhouse gases, and emissions are projected to grow by up to 50% by 2050 if the industry continues on a business-as-usual path. Governments in 2018 pledged to cut shipping emissions in half by 2050, but industry has been slow so far to implement measures on the ground.

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It takes a lot of energy to haul a ship through the water – and there are an increasing number of ships to haul as world trade grows. To cut emissions, some of this energy could be reduced through ships using more efficient designs, installing technologies to harness wind, going a bit slower to conserve fuel, or simply transporting less things.

But ultimately, if shipping is going to fully decarbonise – and it will have to if the world is to stay within safe temperature limits – it needs to find a replacement for fossil fuels.

If we are to keep the world within safe temperature limits, shipping needs to find a replacement for fossil fuels (Credit: Getty Images)

CMB’s hydrogen programme is one of several shipping projects across the world testing how hydrogen and other fuels made from it, such as ammonia and methanol, could be used to power a low-carbon maritime industry of the future. These fuels, together often called “synthetic” fuels, are seen as a particularly promising option because they can be made using clean electricity – such as solar or wind power – and burned without emitting any greenhouse gases.

Why hydrogen?

Hydrogen isn’t the only alternative fuel option, of course. Biofuels – fuels made from plant materials or animal waste – are another. But these have a large array of planned uses in other sectors while their sustainable production is limited, says Tristan Smith, a shipping emissions researcher at University College London.

Batteries charged using renewable electricity are another option. But there will likely be limits on the distance these can power; large ships crossing oceans would simply need too many batteries to run on these alone.

Nearly all hydrogen is produced using fossil fuels – in fact, 6% of global natural gas and 2% of coal currently goes to hydrogen production

Which leaves hydrogen and other synthetic fuels made from clean electricity. The gas is already widely used in industrial processes across the globe – demand for it has increased three-fold since 1975. But nearly all hydrogen, which is already used heavily in industry, is produced using fossil fuels. In fact, 6% of global natural gas and 2% of coal currently goes to hydrogen production. While this kind of hydrogen could be used to power ships with zero emissions from the ship itself, obviously it is not low-carbon since fossil fuels are used to produce it.

But hydrogen also can be produced without fossil fuels, using renewable energy to split water in a process called electrolysis. This process is expensive, and currently just 0.1% of hydrogen is made using it, but this is where the main hope lies for a climate-friendly shipping fuel. “Green hydrogen can be really emission-free on a full lifecycle basis,” says Marie Hubatova, a shipping emissions expert at the Environmental Defence Fund. “That means from the point of where the fuel is extracted, or produced, until the point of combustion.”

Toshiba’s test plant produces hydrogen through electrolysis, rather than using fossil fuels – a process used to make just 0.1% of hydrogen (Credit: Yoshikazu Tsuno/Getty Images)

The problem is that right now, the availability of green hydrogen is just not there, says Xiaoli Mao, a researcher on the marine team at the International Council on Clean Transportation (ICCT). “Fuel producers need to see some legitimate demand in order to invest into its production, so it’s sort of like a chicken/egg problem – whether the ship technology develops first or the fuel side develops first,” she says.

CMB itself is already acting as an early mover by building its own maritime refuelling station for hydrogen cars, buses and ships in Antwerp port, which will produce its own hydrogen using an electrolyser. “We first need to show, look, we are customers and we are willing to pay that amount for hydrogen,” says Campe. “And then you see, ‘Oh, there’s a business case for the electrolysers’.”

How it works

Once the hydrogen is produced, there are several ways it can be used to power ships.

It can be burnt in an internal combustion engine, as Hydroville is currently doing. One downside to this is that burning anything in air, which consists largely of nitrogen, inevitably produces some level of nitrogen oxides – which are major air pollutants.

The Hydroville’s drivetrain operates via hydrogen (Credit: CMB)

These emissions could be tackled by fitting some kind of after-treatment device, says Mao. But hydrogen can also be used in a fuel cell – a device which chemically converts the fuel into electricity without the need to burn it, and the only emission is water. “The main challenges of making that work on a ship are just to make it big enough,” says Smith, noting the huge expense of installing enough fuel cells to power a ship. “There’s a real question as to whether or not that is an option that is going to work at the scales of vessels.”

Further options may exist for hydrogen. One UK company, Steamology, is in the early stages of developing steam-powered hydrogen electricity. Here, steam created by burning hydrogen with pure oxygen from a tank is used to drive a turbine, generating electricity. The technology is currently being tested in trains but has strong potential to be used in the shipping sector, its founders say. “It’s quite crude in many ways,” says Matt Candy, CEO of Steamology. “So we believe that we’ve got both a steam-electric solution. We don’t have any nitrogen oxides, we are genuinely zero emission. But we’ve got to go through the pain of burning hydrogen in an oxygen environment.”

Despite these promising technologies, switching to hydrogen fuel does not come without major challenges.

For a start, it’s highly flammable. CMB runs training programmes for its crew and others, looking at everything from how to maintain a hydrogen system on board a ship to how to handle fire safety. It is also very expensive, although its costs are falling, and will require extra electricity capacity.

As hydrogen is highly flammable, CMB is having to train its crew in new safety protocols (Credit: CMB)

But the real challenge for using it in long-distance shipping is how tricky it is to store. Hydrogen cannot simply replace bunkering fuel in the current system. To store it on board a ship as a liquid, it needs to be frozen using cryogenic temperatures of -253C (-423F), says Hubatova. And even then, it takes up a lot of space – around eight times more than the amount of marine gas oil needed to give the same amount of energy, according to EDF analysis.

The extra space needed by hydrogen has caused concern in the industry that it might need to clear out cargo to make room for the fuel. But an analysis from the ICCT has found that this barrier could be overcome. It found that 43% of current voyages between China and the United States – one of the world’s busiest shipping lanes – could be made using hydrogen without the need for cargo space or to stop more times to refuel. Nearly all the voyages could be powered by hydrogen with only minor changes to fuel capacity or operations, it found.

Ammonia alternative

Hydrogen is often used as a catch-all term for synthetic fuels, but many experts believe another option is actually better: using the green hydrogen to make green ammonia, another fuel which can be either combusted or used in a fuel cell. Ammonia is far easier to store than hydrogen (it needs refrigeration but not cryogenic temperatures), and takes up around half the space since it is far denser. It can also be converted back to hydrogen onboard a ship, meaning it could be loaded and stored on the ship as ammonia but ultimately used in a hydrogen fuel cell.

“At the moment, the best bet is to just turn [hydrogen] into ammonia, which is this ‘Goldilocks fuel’,” says Smith. “Ammonia is so much cheaper to store; you can store it at a pressurised tank, so you don’t need to have any sort of cryogenics. It’s only a small amount more expensive to make than hydrogen.”

An experimental hydrogen boat from France’s Energy Observer tests types of renewable energy (Credit: Peter Kovalev/Getty Images)

The caveats? First, ammonia is toxic to both humans and to aquatic life, so care will be needed. Second, the extra step to convert hydrogen to ammonia will use more renewable electricity, making ammonia that extra bit more expensive.

Still, ammonia is seen by many in the industry as the most viable option: a consortium of companies were recently granted EU funding to install the world’s first ammonia-powered fuel cell on a vessel in 2023.

Green hydrogen itself is already pricey, and for a long time many have doubted whether it could ever be cheap enough to see widespread use as a fuel. But the huge cost reductions in wind and solar over the past few years have helped to challenge this view, with some experts projecting the cost of green hydrogen to fall significantly more in the next decade.

Necessary change

After a lethargic start to climate action over the past decades, there are some signs the shipping industry is beginning to pay attention to risks posed to it by the climate crisis. According to Smith, large percentages of the industry now think they will need to get off fossil fuels, with hydrogen-derived fuels such as ammonia considered the most likely alternatives. “There are a million questions about how we get from where we are today to that end goal,” he says. “But the idea that that’s where we’re heading, is now very, very, very, very mainstream.”

Major challenges remain for the industry to decarbonise (Credit: Jerry Lampen/Getty Images)

This is backed up by groups like the Getting to Zero Coalition, a group of shipowners, ports and countries who have pledged to introduce zero-emission vessels on deep sea routes by 2030. Earlier this year the group compiled a list of 66 zero-emission pilots and demonstration projects for shipping around the world, many involving hydrogen fuels. “They will probably be the group which will really pioneer hydrogen and ammonia vessels on a larger scale than pilots,” says Hubatova. “This bottom-up action is really important as it sends the right signal to the wider industry.”

But in the absence of stronger regulation for the shipping industry’s emissions, the speed of decarbonisation will be limited. “The role of the top-down approach in the form of regulations is also crucial, as it will ensure everybody transforms to zero-carbon, not just the most progressive players,” says Hubatova.

We’ve got options: we can either essentially progressively ban fossil fuels on vessels, or we can try and incentivise the market for hydrogen-derived fuels – Tristan Smith

In fact, Smith argues that the main constraint for shipping emissions comes not from technological barriers but from the political process – most significantly, the International Maritime Organisation, the UN body responsible for addressing shipping’s climate impact. “We’ve got options: we can either essentially progressively ban fossil fuels on vessels, or we can try and incentivise the market for hydrogen-derived fuels,” he says.

Smith himself foresees three stages over the next 15 years for hydrogen-derived fuels in shipping: an increase in trials and first-of-a-kinds from now to 2025; an uptake of hydrogen by early movers in the industry by 2030; then a wider scale roll out after 2030, as costs come down and the infrastructure for refuelling becomes more widespread. Already, shipping companies are talking about ordering “zero ready” ships that are ready to easily retrofit for ammonia, he adds. “Their mindset is, I know that in 10 years’ time I’m going to have to do something to run that vessel on ammonia,” he says.

The result for shipping emissions depends on a whole range of factors, from regulations to the uptake of other technologies. But there is a growing body of evidence of how fast the shipping sector could decarbonise if it set its mind to it, with one major report finding it could almost completely decarbonise by 2035 using currently known technologies, including alternative green fuels such as hydrogen.  

One report found shipping could almost completely decarbonise by 2035 using currently known technologies, including hydrogen (Credit: CMB)

Gilpin thinks the sector could reduce emissions by half by 2030. “If we treated this climate emergency, like we’ve treated the Covid emergency, then absolutely we could,” she says. “But we don’t, we go ‘Oh it’s a bit difficult, let’s have another meeting about it.’”

Mao agrees that to ensure widespread uptake of lower emissions shipping technology, stringent mandatory regulations are vital. Even though hydrogen fuels may not see widespread use for a decade or more, she says, “we really need to start now”.

“There are many barriers, let’s face it,” she says. “We should devote our research money into making this a reality into the future.”