Biodiesel: an intriguing decarbonisation option, but questions remain

Carbon insetting

Biofuels are also being used by shipowners in bespoke green voyage services that cater to shippers and non-operating common carriers that want to rein in their Scope 3 GHG emissions.

In September, the 180,432-dwt bulk carrier Lambert Maru, chartered to mining company Anglo America from Mitsui OSK Lines (MOL), bunkered with ISCC-EU certified B30 biodiesel at the Port of Singapore. The ship is part of the Japanese owner’s carbon inset programme framework, Blue Action Net-Zero Alliance, which was launched in 2024 to achieve net-zero emissions in maritime transportation. The GHG reduction value delivered during the voyage will be allocated to Anglo American using digital certification. This allows the mining company to incorporate the information into integrated reports or other disclosures as part of its Scope 3 reduction activities.

MOL estimates the B30 blend will reduce CO2 emissions during the transit by about 30% compared to conventional diesel.

Case study

In its report, DNV presented a case study of an 18,000-dwt chemical tanker operating under the Net-Zero Framework. The class society said present price levels make “a better business case to use biofuel rather than pay Tier 2 penalties. To reach the Base target from 2028 to 2040 by increasingly blending in biofuels, the case study ship starts with 6% of biofuel in its energy mix in 2028, increasing to 78% in 2040.”

But all biofuels are not created equal. If the same chemical tanker was powered by LNG engine technology, the business case falls apart. “Selling surplus units through maximal use of bioLNG for the LNG version of the case study ship is not economically viable with our case study assumptions after 2031, without extra income from premium transport or rewards from the IMO Net-Zero Fund,” said DNV.

But how penalties collected in the IMO Net-Zero Fund are shared and distributed still needs clarifying. An estimated US$10Bn to US$15Bn in penalties will be collected from shipping and deposited annually in the fund.

Impact on components

Another question that needs answering is the long-term impact of using biodiesel on engines, generators, fuel storage and supply systems.

A recent pilot project between Japan’s NYK Line and the Global Centre for Maritime Decarbonisation (GCMD) is attempting to address this knowledge gap.

Called Project LOTUS, the six-month pilot involved assessing the engine performance and operations of the fuel oil delivery systems onboard a pure car truck carrier, following the continuous use of B24 FAME in combination with VLFSO.

Results from the trial reported by GCMD were encouraging. The Singapore-based NGO reported the main and generator engines, which ran on B24 for 2,888 and 1,813 hours, respectively, performed comparably to when they operated on VLSFO.

Key observations from testing and inspections confirmed no excessive sludge in fuel injection valves, no scratches in fuel injection pump plungers, and no liner or piston wear beyond OEM specifications. Scavenge drain and engine oil analyses also showed no excessive wear elements.

While the acid value of B24 blends increased 2.5-fold after six months of storage, the fuel quality remained within ISO 8217 specifications. No microbial growth was observed in fuel samples.

GCMD concluded: “With these findings, OEMs confirmed engine and hardware compatibility with long-term B24 use, with no significant impact on operational costs, provided appropriate maintenance and handling practices are followed.”

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