As the maritime industry navigates the push toward decarbonization, vessel operators are weighing a complex mix of technologies, regulations and fuel options. Workboat operators, in particular, face tough choices as they balance performance, safety and cost while meeting emissions targets.
To explore how this transition is unfolding, Marine Log spoke with Will Watson, product manager – Caterpillar Marine, about the realities of adopting alternative fuels, the promise of hybrid propulsion, and the practical challenges that come with integrating new power solutions into today’s fleets.
Marine Log (ML): How are operators in the workboat sector approaching the transition from conventional diesel to alternative fuels like methanol, LNG, or biodiesel?
Will Watson (WW): Sustainability, efficiency, performance and evolving regulatory requirements are all factors influencing maritime power solutions today and in the future. There are many options available, which can be confusing. Operators are seeking trusted and knowledgeable collaborators to help them navigate their choices, from power solution manufacturers to naval architects to shipyards to integrators, to select solutions that are application and vessel appropriate. Operators want to select solutions that enable them to comply with regulatory requirements while lowering their operating costs and maintaining reliable performance.
ML: What operational or safety challenges do you see most often when operators adopt new fuels?
WW: Shifting to a new type of fuel must be carefully evaluated to understand storage and safety requirements as well as suitability for prime or standby applications. For example, blending fatty acid methyl ester (FAME) with diesel fuel by more than 5% requires increased engine monitoring. In contrast, hydrotreated vegetable oil (HVO) provides the ease of a drop-in diesel replacement that doesn’t require monitoring adjustments.
A fuel’s useable life can also vary. Using FAME as an example again, it has a shorter shelf life and lower oxidation stability than conventional diesel. It’s also more likely to dissolve and absorb water, which can lead to microbial growth and contaminants that may clog filters.
Temperature sensitivity and material compatibility can influence a change of fuel type. Different fuel types, such as hydrogen and liquefied natural gas (LNG), can require special insulation and some lower carbon-intensity fuels are more flammable than others.
Space constraints can require major structural changes to a boat to properly store a lower carbon-intensity fuel. This substantially impacts a vessel’s design and cargo capacity. Price, availability and bunkering infrastructure port to port could vary for certain fuel types. This can complicate operators’ refueling logistics.
This shouldn’t deter operators from introducing lower-carbon power options into their fleet, however. Just as LNG intimidated operators and crews when it was introduced as a marine fuel over 20 years ago, its bunkering is standardized today. We’ll witness this same evolution with fuels such as methanol, ammonia and hydrogen used for marine applications where these lower carbon-intensity fuels are practical.
While operators strive to lower greenhouse gas (GHG) emissions, they must factor all these aspects into their decision making as these alternatives come with unique challenges. They also must plan with flexibility in mind to enable their vessels to remain in service in the coming years even as requirements change.
ML: Hybridization is gaining traction across vessel types. From your perspective, which kinds of workboats stand to benefit most from hybrid propulsion, and why?
WW: It truly depends upon the application however tugboats, offshore support vessels (OSVs) and ferries can benefit from hybridization due to their variable operating profiles. Tugs’ point-to-point operations lend themselves to full electrification or the use of hybrid and electric systems—power solutions that combine the reliability of internal combustion propulsion engines with electric motors, clutches, gensets, power electronics, controls and battery systems.
OSVs tend to operate in standby or dynamic positioning mode, depending on the task, and hybrid and electric systems can effectively manage low load demands.
Ferries and crew transfer vessels (CTVs) run fixed routes—their energy requirements are very predictable. When these types of boats operate in geographies with GHG emissions restrictions, a hybrid and electric system can be especially helpful.
Hybrid and electric systems not only efficiently manage these types of fluctuating power demands but also lower GHG emissions and generate operational savings from decreased fuel use and extended time between maintenance intervals.
ML: Methanol is drawing attention because of its availability and simpler storage compared to other fuels. What are the key considerations for integrating methanol systems into workboats?
WW: Caterpillar sees great potential for methanol as a marine fuel to help operators achieve their sustainability objectives while ensuring reliable power and performance. Methanol has a much lower flash point than marine diesel oil (MDO). With this increased safety risk, LNG safety standards must be followed.
Storage requirements also require additional attention. Methanol tank location, employing a double-walled fuel tank, fuel equipment protection, spill containment, firefighting and vapor and fire detection are all necessities for using methanol onboard. Additionally, oxidation catalyst functionality is required to address formaldehyde in methanol-fueled emissions. This may impact future newbuild design and construction needs.
There are also physical differences to consider. Methanol’s energy density is 2.3 times lower than the density of diesel, so tank volume must double in size to carry enough methanol to maintain the same energy performance as MDO. For tugs, trying to fit the same amount of fuel in a compact design creates a challenge—and it’s one that must be resolved to avoid increased refueling, which can impact vessel utilization. Methanol also requires twice as many fuel lines, which could increase newbuild construction costs by as much as 15-20%.
ML: Hydrogen is seen as a future option but comes with storage and safety hurdles. What developments are needed before hydrogen is viable for widespread use in workboats?
WW: Hydrogen faces significant technical, safety, regulatory, and infrastructure hurdles to be used as a marine fuel. It has unique storage requirements that demand the use of high-pressure tanks or cryogenic storage. Both options absorb valuable space onboard which is already at a premium for workboats.
Hydrogen’s high flammability makes it crucial to train crews on the nuances of this fuel type. Specialized leak detection, ventilation and fire suppression systems are necessary given the industry’s confined engine rooms.
Additionally bunkering facilities are needed to ensure safe and accessible refueling—and green hydrogen is costly and has limited availability. As regulatory requirements for hydrogen evolve and these challenges are addressed, it can become a viable option.
ML: LNG has been used in larger ships for some time. Do you see opportunities—or limitations—for LNG in smaller, mission-specific vessels like ferries or tugs?
WW: LNG can be a compelling option when striving to reduce GHG emissions as it can reduce SOx by 100% and NOx by up to 85% compared to marine diesel oil (MDO). It also benefits from established safety protocols and a bunkering infrastructure that’s growing globally.
However, methane slip can be a challenge—especially for smaller vessels using two- or four-stroke engines. The large, cryogenic storage tanks LNG requires can also be difficult to accommodate on smaller boats. For ferries and tugs that adhere to routes with quick trips, LNG may not be an economical choice.
ML: How do fuel choices affect lifecycle costs for operators, especially when balancing compliance, reliability, and efficiency?
WW: Balancing energy flexibility and total cost of ownership are key to ensure operators can optimize the considerable investments they’ve made in existing fleets while simultaneously reducing GHG emissions—and fuel choices heavily influence lifecycle costs. The fuel selected impacts upfront capital costs, compliance, operating costs due to price volatility and availability, maintenance and operational efficiency. Fuel flexibility is a way that operators can reduce costs and minimize stranded assets.
For tug and ferry operators, hybrid and electric systems can modernize assets while avoiding heavy CapEx investments that are tied to the uncertainty of certain fuel economics and availability.
ML: Looking ahead, do you expect one alternative fuel to dominate in the workboat sector, or will different vessel types rely on different solutions?
WW: What we’ve learned in collaborating with vessel operators, naval architects and shipbuilders is that there truly is not a single solution that fits all applications. What is appropriate for a passenger vessel won’t meet the needs of a tug, for example. Flexibility is key. This is why Caterpillar is focused on fuel flexibility and multiple power options that can be customized for a vessel’s unique needs. Holistic marine power solutions that allow optimal transit speeds, improved fuel efficiency and lower operating costs are a top priority. Lower-carbon intensity fuels are crucial for this reason and complement hybrid and electric systems that reduce diesel fuel consumption.
Given the broad range of operating conditions, variances in fuel availability by region and vessel operator goals we encounter, Caterpillar anticipates an evolving energy landscape in the marine sector. That vision includes an approach that pairs engines or gensets with other methods of generating and storing energy onboard.
EDITOR’S NOTE: Listen to Will Watson discuss future propulsion options on Marine Log’s Listen Up! podcast.
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