Zero-emission Shipping
Electric cars have entered the mainstream, and all major carmakers have programmes to replace most of their existing line-ups with electric models. It is a question of when, not if, electric cars become the dominant technology.
When it comes to ships and boats, however, there is no such consensus. In fact, many people doubt it will be possible to convert long-distance shipping to green fuels. But is that true? What is actually happening in the industry, and what are the prospects for water transportation taking part in the green transition?
The short answer is it depends what kind of boat or ship you’re talking about: dinghy, barge, passenger ferry or container ship. For the longer answer, read on.
Environmental impacts of shipping
Most boats are fossil fuel-powered, which means they release carbon dioxide, carbon monoxide, particulate matter and nitrogen oxides into the atmosphere. Small amounts of engine oil and fuel routinely enter the water, and very occasionally there are catastrophic oil spills. This pollution is both unpleasant and a hazard to people and aquatic life.
Water transportation is currently “only” responsible for around three percent of total CO2 emissions.1 However, that still makes it a very significant polluter. To give a sense of proportion, it produces some ten percent of transport-related emissions, roughly the same as planes, and double the emissions of rail.2 If treated as a country, its emissions would be similar to those of Germany.
In shipping’s favour, it transports most of the world’s goods – around seventy percent, measured in tonne-kilometres. And on a per tonne-kilometre basis, it is much less polluting than other modes of transport: its high emissions reflect both the large volume of goods carried by ships and the long distances they travel.
Electric vessels
Of the main zero-emission technologies, battery electric vessels have come furthest. Provided that the electricity used to charge their batteries is reasonably green, they greatly reduce GHG emissions, and they have the added benefit of almost eliminating local air and water pollution. This has been cited as one of the key reasons for introducing electric ferries in heavily polluted Bangkok.3
There is another advantage that is often overlooked: less noise pollution. Since sound carries extremely well underwater, it is the main way that many marine animals gather and interpret information about their environment: they use sound to navigate, find food, communicate and avoid predators. Human activities at sea, including shipping and energy exploration, have had a profoundly negative impact on their ability to do these things.4
Electric boats also come with many of the same benefits as electric cars: they are cheaper to run, need less maintenance, and have the potential for better performance such as faster acceleration (albeit at the cost of lower range).
Batteries and charging
As well as the costs associated with scaling up a new industry, the main factors holding back electric vessels have been the cost of batteries, insufficient range and the absence of suitable charging infrastructure. Not so different from EVs, really. And as with EVs, cheaper batteries have helped to solve the problem: they make it affordable to use bigger batteries, increasing range and lessening the need for frequent charging.
One key difference is that ships often operate on fixed routes. This simplifies things: you know exactly how far you need to travel between charges and where you need the charging infrastructure to be. On the other hand, many ships also operate more or less continuously throughout the day, which means you don’t have long to charge them between crossings. The technology for extremely fast charging is becoming available, including wireless charging systems that can start to deliver up to 2.5 MW before the ship has even finished docking.5 That is enough to fully charge a small ferry in less than half an hour, and a quick top-up only takes a few minutes. In practice, it can be done much faster than the time it takes to turn around the vessel.
However, there is another problem: in many cases, the local distribution network cannot provide enough power, so the grid must be upgraded. Alternatively, an onshore battery pack can be installed, which is charged more slowly while the boat is at sea. The energy from the onshore pack is then quickly transferred to the boat’s battery pack when it docks. These are not major technical problems for small or medium-sized vessels, although they do add cost and complexity to projects.
Electric ferries
The world’s first plug-in hybrid ferry was MV Hallaig, which entered service in 2013 on a route between Skye and Raasay in Scotland. Less than two years later, it was followed by MS Ampere, the first fully battery electric car ferry. It was introduced on a busy but relatively short route across Sognefjorden, Norway’s deepest and longest fjord.
Since then, progress has been rapid. There are now tens of fully electric ferries operating around the world, including E-ferry Ellen on a 40 km route between the islands of Ærø and Als in Denmark. It recently travelled over 90 km on a single charge, which is a new world record for an electric ferry.
That is also much longer than most ferry routes. For example, the world’s busiest route – the Staten Island ferry in New York, with over 25 million annual passengers – is only 8.4 km long. And Dover and Calais – at either end of Europe’s busiest crossing – are only 50 km apart. Of course, many factors affect the range of electric ferries, including the weather, and the type and size of ship, but with technology constantly improving, it is reasonable to assume that it will soon be technically feasible to operate almost all ferry services using electric vessels. Norway has already committed to powering all its public ferries with electricity by 2030.
The ferry operators in Washington State and British Columbia, which run some of the busiest routes in the world, have also recently outlined plans to electrify all of their ferries6. Rather disappointingly, however, they have gone for the more conservative option of plug-in hybrid ferries, in spite of most of their routes being quite short. Since ships have an expected working life of 25-30 years, these new hybrid ferries risk locking in greenhouse gas emissions for a number of decades. Nevertheless, it is possible to retrofit vessels with additional batteries, and if costs continue to come down, that is likely to happen.
The good news is that over 100 of the world’s 4,500 passenger ferries are already fully electric or plug-in hybrids, with the number rising by the month. One important incentive is that while the up-front costs are higher than for traditional ferries, the long-term operating costs may be as much as 80 percent lower.7 And while none of the world’s biggest ferries are electric yet, there are already plans to change that, with 200-metre-long battery-powered ferries due to hit the water by 2030.8
Other electric vessels
If the news for ferries is promising, what about the rest of the world’s 90,000 or so boats and ships? Unsurprisingly, perhaps, many of the early success stories involve cargo ships of a similar size to ferries shuttling back and forth on relatively short, predictable routes. These include an electric tanker in Japan,9 a cargo ship in Norway10 and a coal carrier in China.11
In the case of cargo ships, it is particularly useful that electric ships have the potential to operate autonomously. This is because the simplicity and reliability of electric motors means there is no need for the traditional engine department. As well as the obvious cost savings this brings, it should reduce the risk of accidents at sea and eliminate any risk to crew in the event of an accident. By making shipping more competitive, autonomous operation may also allow ships to replace road transport even on relatively short trips.12 This would be a huge win, as it would combine the benefits of electrification with the inherent efficiency of water transportation.
The transition to battery power doesn’t stop with ferries and cargo ships. Everything from the gondola-like moliceiros used on the canals of Aveiro in Portugal to pleasure craft, via river boats in Paris and all kinds of dinghies, are rushing to go electric. For tourism and leisure, the quiet and clean operation of electric motors is a huge selling point. The introduction of increasingly strict limits on pollution in inland and coastal waters will also accelerate the shift to electric propulsion.
The final frontier: ocean-going vessels
There may be a clear path for how small and medium-sized boats travelling on relatively short routes can go electric, but the same solutions will not work for the huge ships that ply routes across the oceans, like container ships, bulk carriers and tankers. Their sheer size, and the thousands of kilometres they travel, mean that batteries are not a realistic option. And that’s a serious problem, because these giants of the sea are responsible for over half of all emissions from shipping.
Fortunately, battery-electric propulsion is not the only zero-emission technology. Of the alternatives, biofuels are probably the least promising option. One issue is that you need to compete for the limited supply of raw materials with the electric power sector and road transport, and a more serious concern is that a high proportion of biofuels come from palm oil plantations created by clearing rainforests.13
Another alternative is nuclear propulsion, which is already used in submarines, aircraft carriers and icebreakers. But although it is tried and tested technology, it suffers from the same basic problem as nuclear power stations: high costs, in part driven by safety and security concerns. Consequently, it has never been widely adopted in civilian shipping, and that seems unlikely to change in the foreseeable future.
The final two main contenders are hydrogen and ammonia, which are normally used to power fuel cells. Fuel cells convert chemical energy into electricity in a process that only emits water and warm air. What’s more, they have much higher energy density than batteries, so they can fuel large ships over much longer distances14. That sounds like the perfect combination, but as ever there is a catch: both hydrogen and ammonia are currently produced in energy-intensive processes fuelled by natural gas. That means you are just shifting the real pollution from the ship to the production process for the fuel.
The potential solution is essentially the same for both hydrogen and ammonia, since the latter is made from nitrogen and hydrogen, with 90 percent of the energy required being used to make the necessary hydrogen. That brings us back to “green” hydrogen, which I have mentioned in a couple of my other blog posts. If you can produce the hydrogen using renewable energy – and work is underway to make this possible – you will have genuinely clean fuels for your ocean-going ships.
As well as their many similarities, there are a few important differences between hydrogen and ammonia. For example, hydrogen has higher energy density by weight, whereas ammonia has higher density by volume. And since ammonia can be stored at lower pressure and less cold temperatures than hydrogen, it is cheaper, safer and easier to handle. This also reduces the risk of leaks, which is a serious concern with hydrogen. Both technologies are still in their infancy, but the first hydrogen ferry was launched in 2021,15 and several ammonia-powered ships are under construction.16
Grounds for optimism
There are lots of reasons to be optimistic that the shipping industry will dramatically reduce its environmental impacts over the coming decades. A variety of technologies that eliminate both GHGs and local pollution are coming on stream, with battery-electric propulsion leading the way. And while it will take some time to complete the transition to zero-emission ships, even marine fuel oils are much less polluting than they were in the past.17
From a technological point of view, most new ships could be zero-emission quite soon. For that transition to happen as quickly as possible, governments will need to help with the higher up-front investment costs, work with the shipbuilding industry to eliminate supply chain bottlenecks, enable the necessary grid upgrades and support charging infrastructure.
Zero-emission ships will only truly deserve that name when renewable electricity is used to charge their batteries, or to make the hydrogen and ammonia for their fuel cells. Nevertheless, the long lifespan of ships makes it vital to start the transition now.
https://ec.europa.eu/clima/eu-action/transport-emissions/reducing-emissions-shipping-sector_en
https://tcc-gsr.com/global-overview/global-transport-and-climate-change/
https://www.shippax.com/en/press-releases/thailands-first-fleet-of-fully-electric-passenger-ferries-to-hit-the-water-in-2020.aspx
https://oceanservice.noaa.gov/facts/ocean-noise.html
https://www.wartsila.com/marine/products/electrical-and-power-systems/shore-power/charging
https://plugboats.com/worlds-busiest-ferry-systems-going-electric-hybrid/
https://electrek.co/2018/02/03/all-electric-ferry-cuts-emission-cost/
https://www.ship-technology.com/news/stena-line-battery-powered-ferries/
https://www.maritime-executive.com/article/first-electric-zero-emission-tanker-launched-in-japan
https://www.yara.com/news-and-media/press-kits/yara-birkeland-press-kit/
https://www.chinadaily.com.cn/business/2017-11/14/content_34511312.htm
https://www.ship-technology.com/analysis/crewless-cargo-the-worlds-first-autonomous-electric-cargo-ship/
https://www.transportenvironment.org/challenges/energy/biofuels/why-is-palm-oil-biodiesel-bad/
https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme/green-ammonia/
https://fuelcellsworks.com/news/norway-mf-hydra-the-worlds-first-hydrogen-operated-ferry-wins-ship-of-the-year-2021/
https://eidesvik.no/viking-energy-with-ammonia-driven-fuel-cell/
https://www.barrons.com/articles/new-rules-united-nations-marine-fuel-diesel-low-sulfer-shiping-refiners-cargo-crude-commodities-51577822797