Biofuels Decoded: Which One Is Right for Your Vessel?

Biofuels offer the maritime industry fuel flexibility, however selecting the biofuel that is most appropriate for a given vessel depends upon several factors, such as application requirements and region. Lower-carbon intensity fuels can reduce lifecycle greenhouse gas (GHG) emissions, even though tailpipe GHG emissions are essentially the same. This helps support vessel operators’ climate-related objectives.

Cat^® diesel engines have offered the flexibility to operate on lower-carbon intensity fuels for more than a decade in land-based sectors, and that field-proven technology is now being leveraged in maritime applications.

To determine if biofuel may be appropriate for your vessel, it’s important to understand the advantages and considerations of the primary options available today.

Key Biofuel Options and Benefits

Biodiesel, or fatty acid methyl ester (FAME), can be manufactured using vegetable oil, animal fat, recycled restaurant grease and even natural gas. FAME is often blended with conventional diesel fuels, and many Cat engines can accommodate specific FAME blends depending upon engine guidelines. Three common biodiesel blends are readily available: B5 (up to 5% biodiesel by volume in 95% diesel fuels), B20 (up to 20% biodiesel) and B100 (100% biodiesel), also known as “neat” biodiesel.

Like FAME, renewable diesel (also known as hydrotreated vegetable oil or HVO) is sourced from vegetable oils and fats, however, it’s processed differently and the end product has different chemical properties. HVO, which can be blended with diesel or used at 100% (neat), burns thoroughly and reduces visible smoke and particulate matter. Its performance is comparable to diesel.

Biofuels’ ability to reduce lifecycle GHG emissions stems from their source – the raw material that creates biofuels are waste materials from different industries. Restaurants' cooking grease is just one example of many potential waste-derived feedstocks. As a result, the capacity to produce biofuel from waste raw materials is limited by the production of the waste itself.

Key Considerations to Optimize Biofuel Use

While biofuels offer compelling advantages, there are unique nuances that influence their use. For example, FAME and HVO price and availability can vary considerably based on geographic region. Substantial investments in methanol supply specifically intended for maritime use¹ have already begun, which will positively impact availability and infrastructure.

Blending and operational requirements must also be considered. Blending FAME with diesel fuel by more than 5% requires increased engine monitoring. The type of application must also be weighed when evaluating FAME and HVO. FAME is best suited for prime applications while HVO can be used in both standby and prime applications.

Biofuel stability and compatibility can vary based on the fuel type. FAME 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. For engines with aftertreatment devices, B20 must be used due to naturally occurring metals. Vessel owners should also be aware that FAME’s operability in cold temperatures and its material compatibility differs from diesel. HVO, in contrast, is not only a drop-in replacement for diesel but also can be stored up to 10 years and resists contaminants, oxidation, water absorption and temperature changes.