Alternative Marine Fuels in Shipping: Methanol, Ammonia, LNG, and the New Liability Landscape

The legal conversation around alternative marine fuels in shipping has changed fundamentally. A few years ago, the main question was whether LNG, methanol, or ammonia could realistically support decarbonisation. Today, the more pressing legal question is different: who carries the risk when these fuels are used, how are they regulated, and what happens when the safety, pollution, contractual, and compliance frameworks do not evolve at the same speed? The IMO itself now treats low- and zero-carbon fuels as essential to shipping decarbonisation and identifies ammonia, biofuels, electric power, fuel cells, hydrogen, methanol, and wind among the main future options, while also stressing that each fuel raises distinct issues of safety, regulation, infrastructure, cost, and adoption barriers.

That is why the subject is no longer just technical. It is a liability landscape problem. LNG is already embedded in a mature mandatory safety regime under the IGF Code. Methanol and ammonia, by contrast, still rely on interim IMO guidance rather than fully mandatory detailed fuel-specific code chapters. At the same time, environmental rules, crew-training rules, EU carbon-cost regimes, and charterparty clauses are developing in parallel rather than in one unified package. The result is a legally uneven transition in which owners, charterers, managers, builders, and insurers may all find that the fuel choice affects not only emissions performance, but also accident liability, pollution exposure, crew-safety obligations, and contract drafting.

Why Alternative Marine Fuels Create a New Liability Landscape

The legal risk starts with regulatory asymmetry. The IMO’s IGF Code is a mandatory international code for ships using gases or other low-flashpoint fuels, but the IMO explains that it is currently focused on natural gas as fuel, meaning LNG is the fuel type with the most mature mandatory safety framework. The Code’s purpose is to provide an international standard and mandatory criteria for the arrangement, installation, control, and monitoring of machinery, equipment, and systems using low-flashpoint fuels so as to minimize risk to the ship, crew, and environment. That framework entered into force on 1 January 2017 together with new mandatory STCW training requirements for personnel on ships subject to the IGF Code.

Methanol and ammonia are in a different position. The IMO’s official alternative-fuel safety page lists MSC.1/Circ.1621 as the interim guidelines for ships using methyl/ethyl alcohol as fuel and MSC.1/Circ.1687 as the interim guidelines for ships using ammonia as fuel. The IMO’s current climate page also lists these fuel-specific interim guidelines and makes clear that work continues on developing the wider safety regulatory framework for alternative fuels. In legal terms, that means shipowners using methanol or ammonia are operating in a regime where the global framework exists, but much of it is still interim, not yet crystallized into the same kind of mature mandatory structure that LNG already has.

That matters because legal certainty in shipping often depends on whether the relevant rules are settled, mandatory, and consistently recognized across flag, class, port state, training, and commercial practice. When a fuel sits inside a mandatory code, it is easier to allocate responsibility around design, operation, crew competence, and inspection. When it sits inside an interim guidance regime, owners and operators may face more reliance on alternative design approval, case-by-case administration decisions, and evolving industry practice. That is a major part of the new liability landscape.

LNG: The Most Mature Legal Framework, But Not a Risk-Free One

Among alternative fuels, LNG currently offers the highest degree of regulatory certainty. The IMO states that SOLAS chapter II-1 and II-2, together with the mandatory IGF Code, regulate ships using LNG as fuel. The IMO also explains that the IGF Code focuses initially on LNG and that it entered into force on 1 January 2017 along with mandatory minimum training requirements for seafarers serving on ships subject to the Code. For owners, builders, charterers, and financiers, that matters because LNG-related safety duties now sit inside a comparatively mature legal architecture covering ship design, machinery arrangement, operational systems, and crew competence.

But LNG does not remove liability risk. It changes its shape. The core legal exposure for LNG ships is less about absence of a framework and more about failure to comply with a clear framework. If an LNG-fuelled vessel suffers a casualty linked to bunkering, gas handling, fuel containment, training, or system design, the legal analysis will often begin with the mandatory IGF Code structure and the STCW training requirements applicable to those ships. In that sense, LNG may create fewer questions about which rules apply, but more direct questions about whether the owner, builder, manager, or operator complied with rules that are already well established.

LNG also creates a second layer of liability exposure through climate regulation. IMO’s GreenVoyage2050 regulatory mapping says that while MARPOL Annex VI regulates LNG-related CO2 and NOx emissions, fugitive methane emissions are not currently regulated under MARPOL Annex VI. By contrast, the European Commission’s FuelEU Maritime page says the Commission has already issued interim guidelines for reporting and verification of actual tank-to-wake methane slip emissions from marine diesel engines within FuelEU Maritime. In legal terms, this means LNG owners may face a situation where global MARPOL air-pollution law is still incomplete on methane slip, while EU regulation is already moving into more detailed methane-accounting territory.

That asymmetry is part of the new liability landscape. A ship may be fully compliant with one layer of international rules while still facing commercial and regulatory pressure under another. For LNG-fuelled ships trading in or to Europe, methane-slip reporting and verification may become relevant not simply as an emissions issue, but as a charterparty cost-allocation, FuelEU compliance, and evidence issue.

Methanol: A More Flexible Fuel, but a Less Settled Liability Structure

Methanol has grown rapidly as an alternative marine fuel, but its legal position remains more transitional than LNG’s. The IMO’s official safety-guidelines page lists methanol and ethanol under MSC.1/Circ.1621, and the IMO’s climate page confirms that interim guidelines for ships using methyl/ethyl alcohol as fuel have already been developed. The IMO’s GreenVoyage2050 regulatory mapping goes further and says that SOLAS chapter II-1 and II-2 regulate low-flashpoint fuels through the IGF Code and SOLAS alternative design provisions, but that the IGF Code does not include detailed methanol-specific requirements, so methanol is presently addressed through the interim guidelines instead.

This has two legal consequences. First, methanol projects still lean more heavily on alternative design and arrangement methods under SOLAS, because the mandatory code is not yet methanol-specific in the way the LNG framework is. Second, there is more room for legal argument if something goes wrong: was the design equivalence adequate, were the hazard controls sufficient, was crew training appropriate, and did the operator rely on a system whose legal framework was still interim rather than mature? Those questions can be expected to feature in casualty, warranty, class, and insurance disputes involving methanol-fuelled ships.

Methanol also highlights how environmental liability does not align neatly with fuel branding. The IMO’s GreenVoyage2050 mapping states that methanol is assigned Category Y under the IBC Code, meaning it presents a hazard to marine resources or human health, but it also says that MARPOL Annex II requirements do not apply to spills and discharges of methanol as fuel. At the same time, the same mapping notes that MARPOL Annex VI regulates CO2 and NOx emissions from methanol use. This suggests a regulatory structure in which the air-emissions side is more developed than the fuel-spill side. That is not a complete absence of liability, but it does mean the liability framework for a methanol-fuel incident may be less settled and more dependent on general maritime law, domestic pollution law, or contractual allocation than parties might expect.

That gap matters in practice. A methanol-fuelled ship may offer commercial advantages in FuelEU and decarbonisation planning, but the legal treatment of leaks, spills, and operational incidents may still be less straightforward than the mature oil-fuel framework or the better-developed LNG safety regime. In short, methanol improves some regulatory positions while complicating others.

Ammonia: The Most Difficult Fuel in Liability Terms

Among the major alternative marine fuels, ammonia probably creates the most distinctive liability profile. The IMO’s MSC.1/Circ.1687, dated 26 February 2025, states that the Maritime Safety Committee approved interim guidelines for the safety of ships using ammonia as fuel at its 109th session in December 2024. The circular itself emphasizes that the guidelines are provisional, are intended to provide a high-level goal-based standard, and require future revision once operational experience becomes available. It also states that the purpose of the guidelines is to minimize risk to the ship, its crew, and the environment, and that the current version does not yet contain detailed provisions for every case.

That provisional status is legally significant. It means ammonia-fuel projects are operating in a framework where the IMO has recognized the need for international guidance and has issued it, but the regime is still explicitly described as interim and goal-based. This creates a broader zone of judgment for administrations, class societies, shipbuilders, and operators. It also means that liability disputes may turn heavily on whether the owner and its technical chain genuinely achieved an equivalent level of safety rather than merely pointing to compliance with a fully mature detailed code.

Ammonia also raises more acute crew and human-safety issues than many conventional marine fuels. The IMO ammonia guidelines define a source of release as a point where an explosive and/or toxic atmosphere could be formed, define toxic areas and toxic spaces, and require that ammonia-related hazards be minimized through design features such as ventilation, detection, containment, and safety actions. The guidelines also say unintended accumulation of explosive, flammable, or toxic concentrations should be prevented and that sources of ammonia release should be minimized to reduce exposure to humans and the environment. In practical legal terms, ammonia liability is therefore likely to focus heavily on crew safety, occupational exposure, emergency response, and toxic-release management, not just on ordinary machinery safety.

The environmental side is also underdeveloped compared with the safety side. IMO’s GreenVoyage2050 mapping says that ammonia as fuel is not yet covered by a detailed IMO pollution regime equivalent to the safety regime; it notes that MARPOL Annex VI currently regulates NOx, that N2O emissions are not currently regulated under MARPOL Annex VI, and that fugitive ammonia emissions are not currently regulated there either. The same mapping also notes that MEPC has agreed on work to develop guidelines for ammonia effluents. That combination is important: safety regulation for ammonia has moved forward faster than its pollution and emissions framework. That is a classic marker of a new liability landscape.

Training and Crew Liability: A Growing Exposure Point

One of the clearest legal consequences of alternative fuels is that they place new pressure on training obligations. For LNG-fuelled ships, the IMO states that the 2017 IGF regime entered into force together with new mandatory STCW minimum training requirements for personnel on ships subject to the IGF Code. That means LNG already sits within a specific training and qualification framework.

For the broader alternative-fuels market, the IMO has now moved further. Its Preparing seafarers for the energy transition page states that IMO issued STCW.7/Circ.25 in September 2025, containing generic interim guidelines on training for seafarers on ships using alternative fuels and new technologies. The same IMO page says fuel-specific interim training provisions for methyl/ethyl alcohol, ammonia, hydrogen, LPG, battery-powered ships, and fuel cells are being developed for consideration in 2026. In legal terms, that means crew-training duties are becoming more explicit even where the fuel-specific safety regime is still interim.

This matters because personal injury, occupational illness, toxic exposure, bunkering mistakes, and emergency-response failures are all litigation risks that can move beyond regulatory compliance into private claims. As alternative-fuel incidents increase, claimants will likely ask not only whether the ship had the right systems, but whether the owner had provided fuel-appropriate training and emergency preparedness. The more toxic and operationally novel the fuel, the stronger that argument is likely to become.

Decarbonisation Rules Change the Liability Analysis

Alternative fuels also reshape legal exposure through decarbonisation regulation, even when there is no casualty. The European Commission’s FuelEU Maritime page states that FuelEU applies to ships above 5,000 gross tonnage calling at European ports and sets annual GHG-intensity reduction targets beginning with -2% in 2025 and reaching -80% in 2050. The Commission also emphasizes that FuelEU is technology-neutral, meaning methanol, ammonia, LNG, biofuels, electricity, and other options may all be used, but their compliance value depends on their lifecycle and onboard emissions profile.

The legal significance is that fuel choice now affects not only design and safety, but also annual compliance exposure. LNG may benefit from established infrastructure and a mature safety code, but methane slip can weaken its regulatory position under FuelEU. Methanol and ammonia may improve some carbon-compliance outcomes, but they may create more difficult safety and toxic-release liabilities. In other words, alternative fuels no longer change only the ship’s engineering profile. They change the ship’s legal cost profile as well.

The EU ETS adds a second cost layer. The European Commission’s ETS FAQ states that the shipping company always remains the responsible entity for surrendering allowances, but that if another entity is responsible under contract for the purchase of fuel and/or the operation of the ship, the shipping company is entitled to reimbursement for ETS costs. The Commission also says the parties are expected to develop contractual clauses and defines “operation of the ship” for this purpose as determining the cargo carried or the route and speed of the ship. That means alternative-fuel decisions now sit directly inside charterparty reimbursement and cost-allocation disputes.

Charterparty Allocation: Why Fuel Choice Must Now Be Contracted

That regulatory reality is why BIMCO’s carbon-clause suite matters so much. BIMCO’s ETS Allowances Clause for Time Charter Parties 2022 says its purpose is to allocate the costs and responsibilities for obtaining, transferring, and surrendering emissions allowances, and that the basic logic is that the party paying for fuel under the time charter is the party that must provide and pay for the allowances, while owners monitor emissions and provide the data used for calculation. BIMCO’s FuelEU Maritime Clause for Time Charter Parties 2024 similarly assumes that the vessel must comply with FuelEU, requires owners to maintain the monitoring plan and verified reporting, and gives charterers a central role in achieving compliance through the fuels and energy supplied.

This is highly relevant to alternative marine fuels because fuel choice is now a legal allocation issue in addition to a technical one. If charterers choose methanol, LNG, ammonia-derived fuel, or other low-carbon options, the benefits and burdens of that choice need to be addressed in the charterparty. BIMCO’s FuelEU clause expressly deals with compliance balances, penalties, onshore power obligations from 1 January 2030, and even survival of obligations after charter expiry because FuelEU verification and compliance steps continue after the end of the reporting year. That is exactly the kind of drafting that the new liability landscape requires.

The same is true under IMO carbon-intensity rules. BIMCO’s CII Operations Clause for Time Charter Parties 2022 says new carbon-intensity rules require owners and charterers to embrace new ways of cooperation and that charterparties need dedicated clauses to manage those obligations. Because alternative fuels directly affect CII and FuelEU performance, any fuel-transition strategy that ignores charterparty drafting is incomplete.

Shipbuilding, Design Approval, and Warranty Risk

Alternative fuels also change the legal position in shipbuilding and conversion. LNG projects can rely more heavily on the mandatory IGF Code framework, while methanol and ammonia still involve more dependence on interim guidance and alternative design acceptance under SOLAS. The IMO’s ammonia guidelines explicitly state that where corresponding IGF provisions are not fit for purpose, the principles of SOLAS regulation II-1/55 should be used to determine appropriate alternative performance criteria. The GreenVoyage2050 mapping makes the same point for both methanol and ammonia by linking them to SOLAS low-flashpoint-fuel rules plus the alternative-design route.

That matters for liability because the more a project depends on alternative design approval and interim guidance, the more future disputes may focus on whether the design really achieved the required safety equivalence. That can surface in yard warranty claims, builder’s risk disputes, class disagreements, casualty investigations, and recourse actions after an incident. In practical terms, alternative-fuel shipbuilding may produce a more complex liability chain than conventional-fuel construction because the regulatory baseline itself is more dynamic.

The Emerging Legal Pattern

The legal pattern is now clear. LNG offers the greatest regulatory certainty but still faces climate-related legal pressure because methane slip is only partly captured in current rules. Methanol is commercially attractive and increasingly available, but still sits in a less settled safety-and-pollution framework than LNG. Ammonia may offer strong decarbonisation potential, but it currently presents the sharpest legal uncertainty because its IMO regime is still interim, explicitly provisional, and heavily shaped by toxicity and future rulemaking.

That does not mean owners should avoid alternative fuels. It means they must approach them as integrated legal projects. The fuel decision now affects design approval, crew training, emergency procedures, charterparty reimbursement, carbon-cost allocation, emissions reporting, and casualty exposure. In short, fuel choice has become a legal risk-allocation decision as much as a decarbonisation decision.

Conclusion

Alternative Marine Fuels in Shipping: Methanol, Ammonia, LNG, and the New Liability Landscape is ultimately about regulatory unevenness. The IMO has made clear that alternative fuels are central to shipping’s decarbonisation future, but the legal frameworks around those fuels are developing at different speeds. LNG sits inside the mandatory IGF Code and STCW training structure. Methanol and ammonia are governed by interim IMO guidance, with methanol still facing a thinner pollution framework and ammonia carrying the highest toxicity-driven safety burden and the most visibly provisional regulatory position. At the same time, EU ETS and FuelEU Maritime have turned fuel choice into a direct cost, reporting, and charterparty allocation issue.