Conidia Bioscience Ltd

DIESEL MARINE DIESEL BUG IN-DEPTH

The diesel bug in depth

Cruise liner On-deck equipment diesel bug

The marine diesel bug

Marine diesel, along with all diesel fuel, is susceptible to the diesel bug. Diesel bug contamination is usually the result of a consortium of organisms acting together. These organisms usually include moulds, yeasts and bacteria. Whilst there are a fairly large number of organisms known to grow in fuels, the ones most commonly found are the mould Hormoconis resinae, the yeast Yarrowia lipolytica, and the bacteria Pseudomonas aeruginosa. This group of organisms is commonly known as the "diesel bug".

There is more detail on the Diesel Bug Science and Diesel Bug FAQ pages.

Marine Fuel Diesel Bug

Deep sea shipping, in both the commercial and defence sectors, utilises HFO for at-sea navigation. This heavy fuel (bunker oil) is not subject to diesel bug infestations. There is though worldwide governmental pressure to decrease emissions by restricting the use of this grade of fuel. On-deck equipment and inshore navigation engines use standard. Standard diesel carries the same diesel bug contamination risk as all grades of diesel.

Small boats are susceptible to the diesel bug

From January 2011, the risk of diesel bug contamination has increased as a result of the introduction of the latest EU Fuel Quality Directive Gas Oil Requirements. This latest directive applies to Non Road Mobile Machinery (NRMM), including not at sea marine applications. The directive requires lower sulphur and higher biofuel levels in diesel. The new fuel specification is more prone to diesel bug growth due to higher water content and the reduced sulphur level. Sulphur has the effect of controlling the growth of diesel bugs. Water is essential to diesel bug growth.

More detail on this topic can found throughout this site. Please refer to Diesel bug & jet fuel fungus FAQ's, Conidia's online Library, and the Video section where downloads of the Fuel Forum Speaker Powerpoints and videos are available.

Fuelstat™ Marine Diesel Bug Test

Marine diesel bug test

Conidia's fast, accurate on-site test for the marine diesel bug was introduced in December 2010. This 10 minute, pregnancy style test is easy to use and interpret. Better still it needs no special skills, equipment or disposal treatment. This means that marine users only need a pair of gloves, a flat surface and a fuel and/or water sample to find out which diesel bugs are living in their fuel and at what level. The level (negligible, low or high) correspond directly with the action that needs to be taken to remedy the situation.

Negligible diesel bug contamination indicates no further action is required. Low diesel bug contamination indicates the use of a biocide. High levels of diesel bug contamination indicate major intervention is required. This usually involves cleaning the tank and system and either discarding or polishing the fuel before returning it to the tank. If diesel bug contamination has been prolonged the injectors, lines and tank may have corroded. Extensive corrosion has been known to require complete fuel system replacement.

Good fuel hygiene processes, involving regular draining of water, and at least annual testing and treatment for diesel bugs in line with test results, are the key to keeping the problem under control.

Sulphate Reducing Bacteria (SRB)

sulphate reducing bacteria

In response to requests from marine customers, Conidia has marshalled its extensive R&D resources to address the issue of SRB contamination, that is infestation by anaerobic microbes. SRB's are normally found at the bottom of the tank, in the sludge that builds up over time. Major advances have been made towards an innovative, easy to use test for these organisms. Conidia is hoping to introduce the next addition to the test range in 2012.