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

The Global Centre for Maritime Decarbonisation (GCMD) has published a report titled "Quantity assurance in marine biofuel supply chains." This report presents a practical approach to ensure shipowners receive the correct total quantity of fuel and the promised renewable content they have contracted. The trial conducted by GCMD focused on an end-to-end marine biofuel supply chain in real-world operating conditions.

Biofuels are sought not only for their energy value but also for their renewable content and the associated emission reductions. The renewable fraction of the fuel determines the "green premium" and is crucial for calculating GHG emissions and complying with regulations. However, blend ratios like B24 or B30 are typically declared by suppliers rather than independently verified. This verification gap needs to be closed to instill trust in marine biofuel transactions.

Mass flow meters (MFMs) are now the preferred method for custody transfer, providing a transparent and auditable basis for determining the quantity of fuel transferred. Yet, adding Fatty Acid Methyl Ester (FAME) to conventional marine fuels like Very Low Sulphur Fuel Oil (VLSFO) or High Sulphur Fuel Oil (HSFO) can alter the blend's viscosity. This could push the blend outside the validated operating range of the MFM used on the bunker barge.

To ensure measurement integrity, the final blend's viscosity should be evaluated under actual transfer conditions and compared with the MFM's validated operating range. This can be achieved by managing transfer-temperature control or using MFMs validated for broader ranges.

Verifying the renewable fraction in biofuel blends requires specific analytical methods. For blends containing FAME, compositional analysis can be used, whereas hydrotreated vegetable oil (HVO)-based blends need radiocarbon analysis, as renewable and fossil hydrocarbons cannot be distinguished through compositional testing. However, interpreting these measurements can be complex.

Neat FAME may contain up to 3.5% non-ester material, so the measurable FAME content may not match its declared blend ratio. Laboratory methods also have limited precision. Therefore, a discrepancy between the measured result and the declared blend ratio does not always indicate incorrect blending or under-delivery.

GCMD's report outlines the three pillars of its biofuels assurance framework: quality, quantity, and GHG emissions abatement assurance. The aim is to determine whether the fuel is suitable for use, whether it delivers the promised emissions reductions, and whether it contains the contracted quantity and renewable content. Professor Lynn Loo, CEO of GCMD, stated, "Buyers need confidence that they have received both the fuel and the renewable content they paid for.

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."