The global shipping industry, currently under intense pressure to reconcile its massive carbon footprint with the ambitious net-zero targets set by the International Maritime Organization (IMO), is looking toward a familiar resource with newfound interest: ethanol. As the sector grapples with the transition away from heavy fuel oils, a comprehensive new study suggests that ethanol—a fuel already ubiquitous in the automotive and industrial sectors—could emerge as a critical bridge for both modern dual-fuel vessels and the existing, conventional diesel-powered fleet.
Main Facts: Ethanol as the "Hidden" Alternative
The maritime transition to green energy has largely been dominated by discussions surrounding methanol, ammonia, and hydrogen. However, research published by the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping, titled Ethanol as a Marine Fuel: Exploring Its Usability, introduces a compelling argument for diversifying the fuel portfolio. Developed in collaboration with industry heavyweights including NORDEN, TotalEnergies, and ABS, the report outlines the technical and commercial viability of ethanol.
The primary appeal of ethanol lies in its supply chain maturity. Unlike ammonia or green hydrogen, which require massive, nascent infrastructure investments, ethanol production and distribution networks are already well-established in key global markets, particularly the United States and Brazil. This "readily available" status gives it a distinct advantage in a market where fuel availability remains the single greatest bottleneck to decarbonization.
The study categorizes the potential for ethanol adoption into two distinct paths:
- The Methanol-Compatible Pathway: Utilizing ethanol in engines already designed for methanol.
- The Diesel-Blend Pathway: Mixing ethanol with marine gas oil (MGO) for use in conventional diesel engines.
Chronology: From Experimental Blends to Commercial Bunkering
The journey of ethanol from a niche biofuel to a maritime contender has been marked by rapid experimentation and landmark operational milestones.
- Early 2025: Maersk begins dedicated testing of ethanol blends aboard its methanol-fueled container vessel, the Laura Maersk. The trials start conservatively with a 10% ethanol blend, designed to monitor engine performance and stability.
- Late 2025 – Early 2026: As data from the Laura Maersk trials proves successful, the company incrementally increases the concentration of ethanol, testing the limits of the engine’s fuel systems and combustion efficiency.
- June 2026: Maersk achieves a breakthrough, reporting the successful operation of the Laura Maersk on 100% pure ethanol, confirming that methanol-capable engines require only minor adjustments to handle the transition.
- Mid-2026: The industry witnesses a significant commercial milestone in Houston, where the 9,016-TEU Tangier Maersk performs the first commercial ship-to-ship ethanol bunkering of a deep-sea container vessel in the United States. This event serves as a proof-of-concept for the logistics of large-scale ethanol refueling.
- July 2026: Technology providers enter the fray. Caterpillar announces the development of specialized conversion kits for selected MaK engines, signaling a move toward market-ready hardware that allows existing ships to transition to methanol or ethanol.
Supporting Data: Technical Hurdles and Economic Realities
The transition to ethanol is not without significant engineering challenges. The research by the Mærsk Mc-Kinney Møller Center highlights a sharp divide between the relative ease of adapting methanol engines and the complex hurdles of modifying diesel engines.
The Methanol-Ethanol Synergy
For engines already designed for methanol, the shift to ethanol is largely a matter of optimization. Because both fuels share similar chemical properties, engine control units and fuel injection timing can be tuned to accommodate the switch. Furthermore, ethanol’s higher energy density compared to methanol means that ships can potentially achieve a longer operating range with less fuel volume, providing a logistical efficiency gain for long-haul routes.
The Diesel-Ethanol Dilemma
The prospect of using ethanol in the world’s massive conventional diesel fleet presents a more daunting set of problems, primarily concerning safety and fuel chemistry. The study identified two "red flags":
- The Flashpoint Crisis: Safety regulations under the International Convention for the Safety of Life at Sea (SOLAS) mandate a minimum flashpoint of 60°C for marine fuels. The study found that even a 10% ethanol blend crashed the flashpoint to a dangerous 13.5°C. Despite attempts to use additives and biodiesel to stabilize the flashpoint, laboratory efforts were largely unsuccessful.
- Storage Instability: Ethanol-diesel mixtures exhibit a propensity to separate during storage, especially in the cold conditions often experienced at sea. The study noted that all tested blends separated within one week at 10°C, rendering them unsuitable for current fuel handling systems.
To mitigate this, researchers have proposed "onboard blending"—where ethanol and diesel are mixed just seconds before entering the engine. However, this does not address the fundamental safety issue of carrying ethanol as cargo, which remains a primary regulatory obstacle.
Economic Viability and Retrofitting
Perhaps the most optimistic aspect of the study is the cost-benefit analysis. Using a Kamsarmax bulk carrier as a model, researchers estimated that retrofitting a vessel for ethanol-diesel blends would cost roughly 50% less than a full conversion to a dual-fuel methanol engine.
While the baseline scenario shows that ethanol-diesel blends are currently less cost-competitive than very low-sulfur fuel oil (VLSFO), the math changes for specific segments:
- Regional Operators: Ships frequently transiting through Emission Control Areas (ECAs).
- High-Intensity Consumers: Large container vessels consuming over 25,000 tonnes of fuel annually.
- Carbon Pricing: As the IMO’s Net-Zero Framework begins to impose stricter financial penalties on carbon emissions, the economic case for ethanol strengthens, particularly if the fuel is sourced with low lifecycle carbon intensity.
Official Responses and Industry Perspectives
Major engine manufacturers, including Everllence, WinGD, Wärtsilä, and HD Hyundai, have publicly supported the research, reporting their own internal testing successes. These entities are pivoting to provide the necessary hardware—conversion kits and software updates—that will allow shipowners to hedge their bets.
However, industry analysts caution that technology is only half the battle. The "sustainability" of ethanol remains a point of contention. Not all ethanol is created equal; its carbon footprint is dictated by the feedstock (e.g., corn vs. agricultural waste), farming practices, and the energy sources used in the distillation process. Consequently, shipowners are advised that adopting ethanol is not a "plug-and-play" solution for net-zero; it requires rigorous supply chain auditing to ensure that the lifecycle emissions reduction is legitimate.
Implications: A Strategic Bridge or a Dead End?
The move toward ethanol carries significant implications for the global maritime landscape.
First, it offers a pragmatic lifeline for shipowners who are currently "stuck" with conventional diesel assets. Instead of forced early retirement for vessels, ethanol offers a potential mid-life upgrade that is far cheaper than full engine replacement.
Second, it challenges the "methanol-only" narrative that has dominated the alternative fuel conversation. By demonstrating that methanol-capable engines can also burn ethanol, manufacturers are creating "fuel-agnostic" or "multi-fuel" vessels, effectively de-risking the massive capital expenditure of new-builds against future fuel price volatility.
Third, the regulatory landscape will need to evolve. The current SOLAS requirements regarding flashpoints were written for a world of fossil fuels. If the industry is to adopt ethanol at scale, international regulators will need to develop new safety protocols for onboard blending and hazardous material handling that reflect modern technical capabilities.
Ultimately, the findings from the Mærsk Mc-Kinney Møller Center suggest that ethanol will not be the "silver bullet" for shipping. It is not an immediate replacement for the entire global fleet. Instead, it is a high-potential, context-dependent solution. Its role will likely be determined by the regional availability of sustainable feedstocks and the speed at which engine manufacturers can standardize the safety systems required to manage ethanol’s unique physical properties.
As the 2030 and 2050 decarbonization deadlines loom, the shipping industry finds itself in a race against time. Ethanol, with its existing supply chains and potential for cost-effective retrofitting, has officially secured its place as a serious candidate in the maritime energy transition. Whether it becomes a dominant fuel or a specialized niche will depend on the next phase of research: determining how to scale the production of truly sustainable, low-carbon ethanol that satisfies the stringent environmental demands of a warming planet.
