Investigation of Microbiological Processes in Fuels

Fuel samples are tested for microbiological contaminations. Photo: OWI

Currently, the steady development of fuels for the heating market is basically focused on the admixture of regenerative fuels, such as fatty acid methyl ester (FAME) or hydrated vegetable oil (HVO). According to the new standard DIN SPEC 51603-Part 6 the admixture of FAME up to 20 % to the product low-sulphur heating oil extra light (HEL) is already possible. When these fuels are used, the oxidation, thermal and storage stability are important product characteristics in order to preserve distinctive features and thus the applicability during the storage in oil tanks over several years.

But despite the quality management and adherence to all standards by the fuel producers, microbiological contaminations of liquid fuels in heating oil systems arise, although seldom and irregularly during the storage. These microbiological contaminations can lead to system breakdowns. Individual case analyses are carried out at OWI, in order to determine causes, effects and possible countermeasures in case of detection of microbiological processes.

As it can be assumed that microbiological contaminations are facilitated by regenerative fuels, OWI analyses in preventive basic investigations (e.g. project “Microbiological Contaminations“) which physical-chemical characteristics of regenerative fuels (and fuel mixtures) lead to microbiological contamination and thus can cause an impairment of the operating reliability of oil burning installations. It is, for instance, assumed that in addition to the essential water due to the production process of FAME, important nutrients, such as phosphor, sodium and potassium, are added to the fuel.

Central questions are: Which microorganisms can appear in heating oil, in middle distillates in general, in FAME and vegetable oil as well as in their mixtures? Does the potential of a microbiological load increase, when biogenic fuels are used? If necessary, which countermeasures can be taken apart from additivation? In order to answer these questions, microbes in liquid mineral oil based and biogenic fuels are identified and the presence of critical ingredients which influence the growth of microbes significantly are verified.