The company points out that adapting vessels and operating procedures to comply with the requirement for lower sulphur levels has been demanding enough without the additional challenge of supply interruptions. Upcoming shortages of 2015-spec MGO are bound to impact pricing as well as availability, forcing operators to consider in house sulphur abatement measures or even burning diesel, which may be more available.

There are engineering implications of further reducing sulphur content. As well as being a lubricity improver, sulphur is known to inhibit microbial growth. Microbial growth in fuels can block filters, wear injectors and, if left unchecked, can corrode tanks.

The increased use of bio-fuels is thought to exacerbate the problem because they have the organic compound FAME (fatty-acid methyl ester) added. This compound has a high affinity for water and provides additional organic matter to support the microorganisms.

Vessel operators are already dealing with de minimis levels of FAME in MGO, as a result of its inclusion in diesel. This is because diesel deposits trace quantities of FAME as it passes through shared fuel pipelines. FAME levels in diesel can range from 1% to as high as 30% in some applications. The adverse effects of FAME on fuel quality peak around the 30% level but are also evident at the lowest levels too.

FAME attracts and holds onto water, unlike traditional mineral diesel, making water drainage a much more challenging affair. Also it appears to be a more attractive food source for micro-organisms. The two factors combined increase the risk of micro-biological contamination.

What can vessel operators do to reduce risk? Draining water and testing regularly for contamination is a start. An even better course of action is a risk and assessment and remedial plan, so that the situation can be dealt with by specialists such as Conidia as soon as problems present themselves. Conidia claims to offer knowledge, skills and impartiality to assist operators in designing the right combination of testing and remediation strategies to keep vessels moving.

Gerry Herman, technical manager of Conidia Bioscience said: “Regular fuel testing is the only way we can identify a microbial problem. If on testing, the diesel tanks show evidence of moderate levels of microbial contamination then an effective biocide treatment can save the day. If, however, microbial growth has been left unchecked for too long and heavy contamination is detected then a tank clean will be in order.”