Lloyd's Register Flags Risk of Inaccurate Energy Values in Biofuels

FOBAS illustrated the issue with testing that compared measured net specific energy values using ASTM D240 against those calculated under the ISO 8217 formula for various FAME-based blends. Image Credit: LR  

Lloyd's Register's has highlighted the risk of miscalculating the energy content of marine biofuels, noting that standard methods can overstate calorific values and lead to voyage planning errors.

According to its latest FOBAS Fuel Insight covering the first half of 2025, fatty acid methyl esters (FAME) have an energy value of about 37 MJ/kg, compared with around 41 MJ/kg for conventional residual marine fuels.

But the conventional ISO 8217 formula for Net Specific Energy (NSE) does not account for biofuels, meaning energy content of blends such as B30 is often overestimated by about 1.5 MJ/kg.

"This discrepancy can cause inefficiencies in fuel management, particularly for electronically controlled engines that rely on accurate energy inputs," the report said, adding that the gap could result in higher-than-expected consumption and fuel costs.

"To address this, the ISO 8217:2024 standard emphasises the importance of direct measurement and specifies the ASTM D240 Bomb Calorimeter method for the accurate determination of energy content for biofuel blends," it said.

At the same time, the report highlights that biofuel adoption in shipping is continuing to rise, with B30 blends the most common blend ratio.

These fuels are now regularly supplied in Singapore, Algeciras and the ARA hub.

LR says vessels using B30 FAME-based blends have generally reported no operational problems.

The report added that most quality issues observed with these fuels have been linked to the 70% VLSFO portion of the blend - such as high sulfur, cat-fines or sediment levels - rather than to the FAME component itself.

Looking ahead, FOBAS said that while FAME-based blends have so far performed reliably, ship operators must ensure that biofuel blends based on new types of feedstocks entering the market are properly tested before being treated as drop-in replacements.

To view the LR report in full, click here.