In November 2024, the published the first edition of the international standard Methanol as a fuel for marine applications — General requirements and specifications, ISO 6583.
This document applies to methanol from all forms of production, prior to any onboard required treatment, for use as fuel in marine diesel engines, fuel cells and other marine applications. It was prepared in cooperation with ship owners, ship operators, national standards bodies, classification societies, fuel testing services, engine and fuel cell designers, marine fuel suppliers, methanol producers, governmental organizations and other technical organizations, to meet the requirements for methanol supplied as a marine fuel on a worldwide basis for consumption on board ships.
The International Methanol Producers and Consumers Association (IMPCA) has developed , Methanol Reference Specifications, Version 9, and , Methanol Sampling Methods — Procedures for Methanol Cargo Handling on Shore and Ship. However, the IMPCA specifications concerned methanol as a chemical traded as a raw material, and included parameters that were not seen as critical to marine fuel users. Fuel-related aspects were also not covered. Additionally, whereas in the IMPCA specifications, there is only a single grade, it was considered that in terms of a marine fuel type product, there was a need to differentiate between the grades of methanol used by equipment, which can be highly sensitive to off-specification deviations, through to more robust systems that can tolerate a less tightly defined product.
ISO 6583:2024 specifies three categories of methanol:
1Marine methanol grade A (MMA): lists the characteristics considered applicable when using methanol as a marine fuel, based largely on the IMPCA specifications, but with placeholders for additional requirements in respect of lubricity and cleanliness; as represented by the particle counting, on the basis of industry experience
2Marine methanol grade B (MMB): lists the characteristics considered applicable when using methanol as a marine fuel. This is based largely on the IMPCA specifications
3Marine methanol grade C (MMC): although derived from the IMPCA specifications, MMC grade provides for wider tolerances on some of the listed characteristics as compared to MMB
One general difference from the IMPCA specifications for all three grades is that density, at 15°C, is specified, rather than specific gravity at 20°C/20°C, in order to conform to general and the requirements of the International Convention for the Prevention of Pollution from Ships (MARPOL). Annex VI, Regulations for the Prevention of Air Pollution from Ships, as amended.
The document indicates that methanol fuel should not be blended with petroleum derived fuels since these would not combine to form a homogeneous product, given the density differential between methanol and petroleum derived. Accumulated petroleum fuel, which may have cross-contaminated the methanol, can cause damage to an engine set up to operate on methanol.
For further information about the applicable requirements, properties, their limits and test methods, consult the SGS INSPIRE fuel specification database.