Alf Baird surveys the various energy options for greening sea transport, whether for passenger or goods

As with all transport modes, the global maritime sector is required to reduce harmful emissions and rapidly move towards zero-emissions. This presents numerous challenges for shipowners, charterers and financiers in coming up with optimal solutions which are practical and affordable, as well as compliant. Current ship orders and specifications are significant in this regard because ships have an expected operating life of 25+ years, which means ships being delivered in the next few years are expected to still be operating until around 2050. Changing fuel type for a fleet of ships is never a simple matter. Fuel costs account for around one third of total shipping expense and marine fuel costs have a tendency to change suddenly.

Ferries are a major part of the maritime industry, often carrying the bulk of traffic in intra-regional and domestic shipping markets. ‘Scrubbers’ have tended to be the favoured modification option for existing Roll on- Roll off (RORO) ferries, helping reduce CO2 emissions but hardly eliminating them, and still burning fossil fuels. These adaptations are not cheap, usually costing between €2m-€5m per ship depending on its size. Fitting of scrubbers merely extends the life of existing vessels enabling them to comply with lower emission regulations, for now.

New ferries of the larger 180m length for longer overnight routes tend to be specified for Liquified Natural Gas (LNG) fuel. Some have mixed propulsion of LNG and electricity and even larger vessels carrying cars and trucks are being readied for ‘multi-fuels’, i.e., dual fuel engines for diesel/LNG to start with and ‘Ammonia Ready’ to comply with lower emission regulations when these kick-in. Recent huge increase in LNG prices of 350% in the past year means that many operators now use diesel in the dual-fuel engines for much of the voyage, only using LNG and/or battery power for short period manoeuvring in port.

The many thousands of small urban commuter ferries operating worldwide present another challenge. The UK Department for Transport’s Innovate UK Clean Maritime Demonstration Competition provided funding for London’s Thames Clippers/Uber Boats and partners work on different zero carbon options including compressed hydrogen gas, liquid hydrogen, methanol and fuel cells and batteries. Current technology only allows diesels for high-speed ferries, though this is changing. In Norway, ferry company Norled’s 12-year public transport contract to provide high-speed ferry services is largely based around cutting CO2. This will involve continued use of fossil fuels for only the next 6 years whilst Norled is developing a battery concept for all its future fast ferry operations and looking at hybrid designs powered by batteries and low-emission diesel engines.

Biogas is another option and a plant is being readied in Denmark from 2023 to provide a CO2 neutral fuel for ferries. This will be for ferry operator, Samso Rederi, which is building a new gas ferry. Meanwhile, Gotland Line is planning emission-free ships by 2030 which will combine gas and steam turbines able to use multi-fuels.

Battery power has tended to be mainly applicable for smaller and lower-powered vessels and for ferries on short crossings in sheltered sea areas such as Norway’s fjords. The first emission free battery ferry was built in 2015 for a short route of less than one hour duration. However, much larger battery power systems are rapidly becoming available. Battery power is also limited by available shoreside charging capacity.

Publicly-owned, CalMac, built three small 23-car capacity hybrid diesel-battery operated ferries several years ago. These vessels came with a high price tag of around £11-12m apiece, three times the cost of comparable vessels using diesel only. The was only ‘viable’ via state grants to pay for the ships and charging equipment. The considerable extra weight and higher displacement of these earlier battery ferries also calls into question their overall efficiency as they need more power. In addition, CalMac’s order for two dual-fuel LNG ferries at Ferguson was described as a ‘catastrophic failure’, the ships still nowhere near completion after six years of waiting, and with costs spiralling to ten times that of comparable options (perhaps £150m per ship). It is also possible to drastically reduce emissions through selecting superior hull forms and CalMac’s high displacement traditional ‘bathtub’ shaped ferries require twice the power, having twice the emissions of more efficient designs, such as Pentland Ferries proven catamarans.

Stena Line’s Elektra project, run in collaboration with Frederikshavn in Denmark, plans to introduce (by 2030) on the Gothenburg-Frederikshavn route the biggest fully battery energy ship in the world for the three-hour crossing. The two ships envisaged would each carry 3,000 lane metres of trucks and 1,500 passengers, requiring 60-70 MWh battery capacity, which would be re-charged during each one-hour port stay. That requires a 30-40 MW shore connection at either end of the route, implying heavy demands on the shore power grid which is not available yet but will use in Denmark renewable wind energy when installed. So, most of the current battery-operated ferries run on subsidised ferry routes, with much of the added investment cost in vessel systems and shoreside re-charging infrastructure underwritten by state support.

Most cruise ship operators have also opted for scrubbers in the funnels to reduce CO2 emissions on existing vessels, whilst for new boats they specify LNG. P&O Cruises’ Iona is the first of its two LNG-fuelled cruise ships. Other environmental features include installing advanced waste water treatment plants, new food waste treatment facilities and fuel saving boilers. MSC Cruises are currently planning to build one of the world’s first oceangoing hydrogen-powered cruise ships in a joint initiative with Italian state-owned shipbuilder, Fincantieri, and Italian energy infrastructure company, Snam. The new ship is expected to allow for zero emissions using a hydrogen bunkering system. The next stage in the preparatory work is planning the arrangements onboard the ship to accommodate hydrogen fuel technologies and fuel cells, and undertaking the technological and economic analysis of hydrogen supply and infrastructure.

Denmark’s Maersk Line has recently ordered eight 350m long, 16,000 twenty-foot equivalent containers (TEU) container ships which will run on methanol. Improved hull design allows for 20% energy efficiency saving per transported container, also permitting faster port working. Meanwhile in the bulk sector, Himalaya Shipping/Golar has placed orders in China for 12 LNG-fuelled bulk carriers.

As of December 2021, there were over 50 ships on order with engines designed to burn methanol. Its plentiful availability is a key factor (unlike ammonia which is rather more restricted currently). Most main ship engine manufacturers are extending product lines to include methanol. Producing ammonia from renewables is expected to take longer to develop. E-methanol (made by renewable electricity) is considered the second least-costly alternative maritime e-fuel. One report found renewable fuels most suited to international shipping are methanol and ammonia, primarily in the form of advanced biofuels and e-fuels. Bio-methanol and renewable e-methanol require little to no engine modification and can provide significant carbon emission reductions in comparison to conventional fuels. From shipowners’ perspectives, flexibility is crucial in minimising financial risk and disruption of operations. As leaders in the field, the Norwegian government is funding several pilot projects led by private shipping groups to develop the first fleet initially of bulk vessels fuelled by ammonia, with ships due to enter service from 2024.

Norwegian research organisation, SINTEF, found that e-methanol comes at lowest additional capital expenditure for vessel operators. The e-ammonia and e-methanol pathways, while requiring higher initial investment, offer the highest fuel choice flexibility both in the medium and long term. Researchers at a Swedish university looked at total cost of ownership for large ferries operating on biofuels, bio-electro-fuels, and e-fuels, in terms of fuel production, fuel infrastructure, ship capital expenditure, energy storage, and loss of cargo space. They found renewable bio-methanol and e-methanol show the lowest cost for each fuel category beating the likes of ammonia and hydrogen.

The weight of evidence suggests sustainable, renewable ammonia and methanol are key intermediate and long-term fuels for the shipping industry, but only methanol can reduce maritime emissions satisfactorily in the near-term. The volumes of renewable methanol product set to come onstream in the next decade will help the industry understand the policy, regulation and economics of the net zero carbon economy while the millions of tonnes of renewable ammonia required can be planned for and produced. The industry is starting its move towards ammonia now: French shipping investors having ordered four large ammonia carriers with China State Shipbuilding Corp also being powered by ammonia. Liquid ammonia can be used as an intermediate carrier for hydrogen, offering a transport solution for large capacity liquid hydrogen.

Norwegian firm, Konsberg, tested and verified a full-scale, full-size, zero-emissions drivetrain powered by hydrogen fuel cells designed for ships and ferries. The testing mirrors operating loads for a small car ferry operating a short route under one hour duration. The project, part of an EU-funded initiative, demonstrates the technology is now available for using hydrogen as an energy carrier. Meantime, a consortium is seeking to deliver another innovative solution with hydrogen as fuel. The aim is to have a scalable and sustainable solution by producing hydrogen onboard using readily available LNG; this solution is expected to be viable in a much faster time than would otherwise be possible. The approach is based on combining LNG with steam to produce hydrogen and CO2. The hydrogen produced will be used directly in a mix with natural gas in internal combustion engines or in fuel cells, thus, eliminating the need for hydrogen to be stored onboard. The CO2 will be liquefied using the cryogenic stream of LNG that would be used as fuel anyway, and later disposed ashore for carbon storage. Tankers can use the stored CO2 as inert gas during discharge. The necessary equipment would be fitted on the deck of a commercial vessel. This would enable the marine sector’s gradual transition from LNG to hydrogen, without major adjustments to a vessel’s onboard technologies.

Ports are also rapidly developing clean emission strategies. Typical of this Kiel which has set itself the goal of reducing its CO2 emissions to zero by 2030. The port’s plan envisages covering 60% of the energy requirements of ships calling at Kiel with green electricity as early as 2022 and by 2025 to reach 80% to 90%. Main actions include installation of shoreside electricity connections for vessels, clean energy vehicles and cranes for moving freight within the port area, including trucks and trains.

In summary, there are many positive zero-emission initiatives ongoing, most involving some form of public support for research and development but all driven by innovative private sector actors. Whilst batteries and LNG have a role, the key focus has moved towards alternative fuels such as methanol, ammonia and hydrogen. There are also different solutions for different ship types depending on length of routes and fuel supply arrangements. A key factor will be development of fuel costs and supply availability as critical elements in the viability of shipping operations moving towards zero emissions. There is, however, some evidence of unnecessarily costly early procurement mistakes made by less astute state-owned ferry operators running monopoly services and lacking advanced ship design expertise or industry insights or discipline; the latter form essential attributes in the case of private operators active in competitive markets where shareholders require assurances that capital is well managed in an uncertain environment.

Alf Baird was formerly Head of the Maritime Research Group and Professor of Maritime Business at Edinburgh Napier University