GCMD outlines practical approach to quantity assurance in marine biofuel supply chains

Image: Global Centre for Maritime Decarbonisation

The Global Centre for Maritime Decarbonisation released its report Aug. 27, “Quantity assurance in marine biofuel supply chains,” outlining a practical approach to help shipowners verify that they receive both the total quantity of fuel and the renewable content contracted.

The approach draws on evidence from GCMD’s end-to-end marine biofuel supply-chain trials conducted under commercial operating conditions.

Biofuels are purchased not only for their energy content, but also for the renewable content and emissions reductions they represent.

The renewable fraction determines the green premium and underpins greenhouse-gas (GHG) emissions accounting and regulatory compliance, yet blend ratios such as B24 or B30 are typically supplier-declared rather than independently verified.

Closing this verification gap will strengthen confidence in marine biofuel transactions.

Ensuring reliable measurement of total quantity transferred

Mass-flow meters (MFMs) have become the preferred method for custody transfer, as they provide a transparent and auditable basis for determining the quantity of fuel transferred.

However, adding fatty acid methyl ester (FAME) to conventional marine fuels, such as very-low sulfur fuel oil (VLSFO) or high-sulfur fuel oil (HSFO), can reduce the final blend’s viscosity, potentially pushing it outside the validated operating range of the MFM installed on the bunker barge.

To maintain measurement integrity, the viscosity of the final blend should therefore be assessed under the actual transfer conditions against the applicable MFM operating range.

This can be managed through appropriate transfer-temperature control or by using MFMs that have been validated for broader ranges.

Verifying the renewable fraction in biofuel blends

Verifying the renewable fraction requires appropriate analytical methods.

FAME-based blends can be verified through compositional analysis, while hydrotreated vegetable oil (HVO)-based blends require radiocarbon analysis because renewable and fossil hydrocarbons cannot be distinguished through compositional testing.

Interpreting analytical measurements, however, is not straightforward.

Neat FAME may contain up to 3.5 percent nonester material, so the measurable FAME content of a finished BXX blend may not exactly match its declared blend ratio.

Laboratory methods also have finite measurement precision.

A difference between a measured result and a declared blend ratio therefore does not necessarily indicate incorrect blending or under-delivery.

Completing GCMD’s 3-pillar biofuels assurance framework

Together, the three pillars of GCMD’s quality, quantity and GHG emissions-abatement assurance framework address whether the fuel is fit for use, delivers the claimed emissions reductions, and contains the contracted fuel quantity and renewable content.

“Buyers need confidence that they have received both the fuel and the renewable content they paid for,” said GCMD CEO Lynn Loo. “This report provides a practical, evidence-backed basis for verifying renewable fuel claims, protecting commercial value and supporting credible GHG accounting as marine biofuel use scales.”

To access the report, click here.