August 27, 2024
The methanol-fueled tugboat design illustrates the challenges facing designers trying to adapt alternative fuel propulsion and generator systems for fishing vessels. Photo: Elliott Bay
The need to reduce emissions from marine diesel engines has led to the introduction of the Tier system in the United States and IMO ratings in Europe. Diesel engine manufacturers serving the US market are building engines with exhaust systems that significantly reduce NOx, CO2 and particulate emissions, but designers are also looking at the feasibility of alternative fuels. A study published in the UK last year detailed the obstacles to using methanol and LNG on commercial fishing vessels, and in the US, Elliott Bay Design Group is applying for a grant to investigate the feasibility of alternative fuels for commercial fishing vessels.
Mike Compreta, Elliott Bay's vice president of strategic expansion, is aware of the challenges. “We have partnered with the American Bureau of Shipping (ABS) to apply for a grant to fund a study on the safety of installing and operating these alternatives on U.S. fishing vessels,” Compreta says. “We have recently had discussions with several groups about electric or alternative fuel power for the processing plant. That could be in the form of alternative fuel powered generators, reformers/crackers, or fuel cells.”
The technology remains complex, including not only harnessing the power of alternative fuels, but also refueling, transporting and delivering the fuel. Compreta points out that hydrogen, for example, requires large storage capacities on board the ship. “But when you combine it with methanol or ammonia as a carrier, you can actually store more hydrogen in a smaller space. Then, to utilize that hydrogen, you need to use a methanol reformer or an ammonia cracker to release it into a fuel cell to make electricity for processing and powering the ship.”
Compreta points out that another option is to use alternative fuels directly in internal combustion engines. “Right now, marine engine manufacturers like Wärtsilä and MAN have engines on the market that can run on a variety of fuels, including methanol and LNG. But most require a blend of around 5 to 15 percent diesel fuel. These are large, low- to medium-speed engines, though. Caterpillar is making high-speed engines that are marketed as methanol-capable. They can be fitted to run on diesel fuel now, and can easily be converted to methanol as the technology matures.” According to Caterpillar's website, the 800-horsepower methanol dual-fuel CAT 3500E engine is scheduled to be installed on a tugboat for field testing in 2026.
Caterpillar is developing the 3500e, a high-speed, 800 horsepower methanol dual-fuel engine, but the project is still in its early stages. Other manufacturers, such as Wärtsilä and MAN, have larger low- and medium-speed alternative-fuel engines on the market.
Implementing this technology on fishing vessels comes with many challenges, and safety is just one of them. “We hold several formal risk analysis workshops,” Compreta says. “We bring everyone together – engineers, fishermen, coast guard – to discuss all the issues that could arise. After considering all the risks, we discuss and agree on the appropriate design and operational features to minimize them.”
Last year, Scotland's Macduff Shipyard published a report listing many of the challenges to incorporating alternative fuels in fishing boat construction, including the need for larger vessels. Macduff estimated costs would increase by 50 to 100 percent, but Compreta's experience with these technologies on other types of vessels suggests they could be much higher. “Everything we've seen has been a 250 to 300 percent cost increase,” he said, noting that the cost of not only the engines but also multiple additional safety systems would be higher. “This is mostly due to regulations, and many of these technologies take 20 years to be 'right-sized' to be viable on fishing vessels,” Compreta said. “But at this point the technology to install hybrid systems is available and costs are falling. If fishermen want to reduce both their fuel costs and their emissions, there are some options they can implement now.”
