Biodiesel can be used as a drop-in fuel to reduce GHG emissions, but questions remain around its price, supply, availability and impact on onboard components
While biofuels are expensive and contain carbon, they offer an immediate solution to help shipowners cut greenhouse gas (GHG) emissions from existing vessels with conventional engine technology.
This drop-in benefit is particularly relevant given the other, more expensive, choices to comply with IMO’s Net-Zero Framework, which was approved at MEPC 83 in April. This has led to an increasing number of pilot projects using various blends of biodiesel.
But all the same questions that surround other alternative fuels – availability, scalability and price – plague biofuels, too. And in the case of biodiesel, the question will be if maritime can compete with other transport sectors for the limited supply.
But biodiesel is still intriguing for shipping. It can be blended with traditional marine fuels to reduce or eliminate penalties under the escalating GHG Fuel Intensity (GFI) targets that were set in the regulation. By blending biodiesel, owners can meet regulatory compliance targets, or bank surplus remedial units for trading or future use. The cost of using biodiesel would have to be balanced against the potential penalties, or the market for trading surplus units.
This year’s DNV Maritime Forecast to 2050 examines the viability of biofuels, with sections exploring potential costs, and considerations around their operational and technical limits. Two of the most widely used versions of biodiesel are fatty acid methyl esther (FAME) and hydrotreated vegetable oil (HVO).
As explained by DNV: “FAME, often called biodiesel, is made from fats, oils, and greases (FOGs) through transesterification, and its exact characteristics depend on the feedstock.
“HVO, or renewable diesel, is produced from FOGs via hydrotreatment, resulting in paraffinic hydrocarbons suitable for most current fuel systems and engines. The fuel properties differ among biofuel products and blend ratios.”
HVO use
Owners across the spectrum – from tugs to tankers – are increasingly piloting biofuels. Earlier this year, Norwegian OSV owner Solstad tested certified HVO in Normand Ferking during the 2007-built anchor-handling tug supply (AHTS) vessel’s transit from Husøya on the west coast of Norway to Rio de Janeiro “to demonstrate that existing measures can effectively cut emissions.”
Propulsion power for the diesel-electric-powered AHTS is normally supplied by four Wärtsilä 8L32 medium-speed engines.
During the transit, the crew focused on saving fuel “by reducing speed and operating with a single engine,” explained Solstad in a social media post.
“OEMs confirmed the engine and hardware compatibility with long-term B24 use”
This resulted in an impressive reduction in CO2 emissions during the voyage. Solstad estimated the vessel saved “more than 95%” of the 1,600 tonnes of CO2 emissions generated with normal speed and “fuel down to 71-t CO2 (net GHG emissions).”
