In a world that’s moving towards more sustainable energy solutions, a new type of marine engine is creating a buzz in the maritime industry. Caterpillar Marine is set to debut its revolutionary dual-fuel Cat 3500E engines in 2026, which could change the way tugboats and other vessels operate. With a combination of diesel and methanol as fuel sources, these engines promise high efficiency, reduced emissions, and greater operational flexibility. However, as the industry explores the potential of this new technology, questions abound about its feasibility and impact.
A groundbreaking engine technology
Caterpillar Marine’s dual-fuel 3500E engines, which integrate both diesel and low-pressure methanol fuel systems, offer a powerful and sustainable solution for maritime operators. The methanol dual-fuel engine, a part of Caterpillar’s 3500E platform, is poised to deliver the same power output as the existing diesel engines which range from 2800 to 3000 bkW while meeting stricter emission standards.
“We’re leveraging our deep dual-fuel expertise to help reduce emissions in the maritime industry,” said Brad Johnson, vice president and general manager of Caterpillar Marine. The dual-fuel Cat 3500E engines aim to meet International Maritime Organization (IMO) Tier III emissions standards, which are more stringent than the current IMO Tier II standards met by the diesel version. The engines are designed to operate with high methanol substitution rates, even at low load conditions, a crucial factor for vessels like tugs that often operate at low speeds.
Andres Perez, Caterpillar’s global tug segment manager, further highlighted the importance of fuel flexibility, saying: “This technology will enable owners to adopt their fuel of choice when the conditions are right without having to build a new asset or face cost-prohibitive retrofits.”
The methanol advantage
Methanol is gaining attention as an alternative marine fuel. It exists in liquid form at ambient conditions, making it easier to store and handle than gases like hydrogen. Additionally, methanol has a lower carbon intensity and good energy density. This makes it a promising option for reducing greenhouse gas emissions in the maritime sector. Caterpillar expects to deploy the first methanol dual-fuel 3500E engines in tugboats by 2026. This will allow operators to run their vessels on diesel for now, but retrofit them to run on methanol when it becomes more widely available.
“Methanol has a promising future in the industry as it is in the liquid phase for storage at ambient conditions, it has low carbon intensity and good energy density,” said Perez. Caterpillar is betting that methanol will become a major part of the marine fuel mix in the coming years, and this dual-fuel engine could help pave the way for its wider adoption.
Why this engine could be a game-changer
The flexibility of the Cat 3500E engine is its key selling point. These engines are optimized for high methanol substitution rates across a wide range of load factors. For instance, a 28-meter tug operating at 8 knots and requiring 600 kW of propulsion power could achieve more than 70% methanol substitution on an energy basis. This would significantly reduce the tug’s greenhouse gas emissions without sacrificing power or performance.
What makes this technology even more attractive is its potential for retrofitting. Tugboats already equipped with the dual-fuel 3500E engines can easily transition to methanol when it becomes available in their regions, without the need for costly and complex modifications. “Fuel flexibility is key to future-proofing assets,” said Perez, underscoring the ability to use whichever fuel is most viable without having to invest in entirely new vessels.
While competitors like Rolls-Royce and MAN Energy Solutions are also exploring alternative engines in the maritime industry, including methanol-diesel engines for tugboats, Caterpillar’s move to offer high methanol substitution rates and the possibility of retrofitting existing vessels gives it an edge in the race to decarbonize the maritime sector.
