The costs of shipping: low prices, high emissions

March 2021 saw the colossal megaship named Ever Given get lodged in the Suez Canal, one of the world’s busiest waterways. The resulting traffic jam involving hundreds of ships severely disrupted trade between Asia, Europe and the middle East. The stranded ship was responsible for holding up an estimated $9.6bn of trade per day.

The crisis highlighted how important shipping is to the global economy. We rely on ships to bring food to our supermarkets and goods to our shop floors. Almost 90% of consumer goods sold in the UK come into the country through shipping. At any one time a staggering 50,000 ships are carrying cargo around the world’s oceans.

Why is shipping so popular? Well compared to air travel it is a comparatively cheap way of transporting goods, adding just 0.3p to the cost of a cup of coffee and 20p to a bottle of wine. However, this convenience comes at a huge environmental cost. Ocean vessels emit more than 1 billion tonnes of greenhouse gases every year. Shipping is responsible for 3% of global emissions, and this is expected to rise to 10% by 2050.

Part of the problem is the sector’s reliance on bunker oil, an extremely polluting fuel that releases greenhouse gases as well as harmful sulphur and particulate matter emissions into the atmosphere when burned.

Recognising that the sector must change, the International Maritime Organisation recently set a target to cut the carbon intensity of all ships by at least 40% by 2030.

So, what are the alternatives to bunker oil?

Ammonia, hydrogen, or methanol?

One option is ammonia, a chemical commonly used to make fertiliser. Ammonia produces no CO2 when burned and can even be used in existing engines. However, it is difficult to combust.

Another possibility is hydrogen, a fuel which has already been used to power cars, planes, and trains. Hydrogen combusts very readily, but storage is a challenge.

But what if the benefits of ammonia and hydrogen could be combined?

At the COP26 Summit in Glasgow, The Science and Technology Facilities Council (STFC) announced a partnership with aircraft manufacturer firm Reaction Engines. Together they will produce a blended ammonia-hydrogen fuel capable of powering the ships and planes of the future.

To make the fuel, liquid ammonia is first heated in a ‘cracking reactor’. The reactor uses a catalyst to partially break the ammonia down into its constituent elements — hydrogen and nitrogen. This results in a blended ammonia-hydrogen mixture that closely resembles the propulsion properties of jet fuel. The fuel mix is then ignited to power the engine, and when completely combusted leaves behind only nitrogen and water vapour. Although toxic nitrogen oxides are produced as a by-product, these can be removed from the exhaust by adding small amounts of extra ammonia.

Meanwhile British startup, ACUA Ocean, is developing a range of uncrewed surface vessels powered by liquid hydrogen.

Uncrewed surface vessels (USVs) are autonomous boats or ships which operate without an onboard crew. They can be used to monitor marine life, collect environmental data, or monitor offshore windfarms.

Most USVs rely on diesel generators, which means they are unable to spend long periods at sea. However, ACUA Ocean has designed a long-endurance USV powered by liquid hydrogen, allowing the vessel to remain at sea for over 70 days before needing to refuel. According to the company, using hydrogen reduces operational CO2 emissions by up to 99.3% without sacrificing power.

Another fuel that could be used is methanol, a type of alcohol. Methanol is a safe, cost-effective fuel that could be produced from renewable sources. It also emits fewer pollutants when burned.

Methanol is one of the fuels being considered by Liverpool-based marine charter company Bibby Marine, who wish to develop a zero emissions fleet in the near future. The firm owns and operates a fleet of service operation vessels (SOVs) which are used to transport maintenance technicians to offshore wind farms. The vessels are currently powered by diesel and electricity, but Bibby Marine but are looking at alternative fuels such as methanol and hydrogen fuel cells.

Making ships more efficient

Another way to reduce ships’ carbon emissions is to make them run more efficiently. For example, by building sleeker, more hydrodynamic vessels that glide through the water, or by improving the efficiency of a ships’ propeller.

This is exactly what Devon-based marine design and manufacturing company Teignbridge Propellers have achieved. They have designed a controllable pitch propeller that enables ships to use fuel as economically as possible in all sailing conditions and at all speeds. The device works much in the same way that an automatic gear box in a car ensures that the vehicle always runs at peak efficiency.

Tests have shown that the propeller can improve efficiency by between 8% — 15% when compared to fixed pitch propellers (FPP). The firm have developed a prototype and aim to launch their full product by the end of this year.

Embracing wind power

Alternatively, we could simply use wind to power our ships. The ancient Egyptians were the first to use sails to propel boats up the Nile River around 4000 BC. Since then, wind-propelled sails and ships have been used by just about every civilisation to conquer, trade with and explore distant lands.

Wind-power is due a comeback, and several companies are exploring how best to achieve this.

One UK company, Smart Green Shipping (SGS), has developed ‘FastRig’ sails that look more like vertical airplane wings rather than the traditional white sails that most people associate with a sailing boat. They can be installed or ‘retro-fitted’ on existing ships, and could reduce carbon emissions by as much as 20%

The sails are paired with a sophisticated software system that can accurately and swiftly calculate the wind speed and direction available to the ship at any one time. The software, developed using meteorological and satellite technology at the European Space Agency’s Business Incubation Centre UK, automatically controls the sail, turning it to make the most of the wind angle and speed, or retracting it when approaching a bridge, or when wind speeds present a danger. It does all this autonomously meaning there is no need for any additional crew to operate.

The winning candidate

So, which of these fuels is the best?

Dr Tristan Smith, Associate Professor in Energy and Transport at University College London leads the Decarbonising UK Freight Transport project, which looks at ways to reduce the sectors’ greenhouse gas emissions. He believes that while batteries, hydrogen and wind power may find a place on smaller boats, larger ships will be powered by ammonia in the foreseeable future.

‘Batteries are an attractive option for ships that are going very short distances and are able to recharge often, for example small ferries, but they don’t work well if you’re sailing across an ocean,’ says Dr Smith.

‘While hydrogen is the cheapest to produce, it’s incredibly expensive to store onboard a ship as you have to use sophisticated cryogenic technology to keep it in its liquid form.’

‘Wind has got lots of potential and is a great way of reducing the overall amount of energy needed to power a ship, but the amount of saving you can achieve on a fleet may not be very large, so it won’t meet the majority of the energy demand for global trade.’

‘We believe that the majority of the world will move over to ammonia over the next decade or two. It’s a well-established chemical that we already produce a lot of for the fertiliser industry. It’s much easier and cheaper to store on board than hydrogen, and you can use it in internal combustion engines so a lot of the engines in existing ships are readily convertible with only relatively small modifications needed.’

Want to know more?

If you’re a UK taxpayer, your contributions helped fund this work, via UK Research and Innovation — the funding body that allocates government funds for research — and the nine research councils.

For more on this topic, listen to our Emissions:Impossible? podcast: How to cut shipping emissions.

ACUA Ocean, Bibby Marine and Teignbridge Propellers were all winners of the Clean Maritime Demonstration Competition (CMDC), funded by the Department for Transport and delivered in partnership with Innovate UK.

Smart Green Shipping uses meteorological and satellite technology provided by the European Space Agency’s Business Incubation Centre UK (ESA BIC UK). The ESA BIC UK is managed, and partly funded, by the Science and Technology Facilities Council (STFC).

The Decarbonising UK Freight Transport project is funded by the Engineering and Physical Sciences Research Council (EPSRC).

To find out more about what UKRI is doing in the race to net zero, listen to our podcast series Emissions:Impossible?

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