Due to changing legislation and emission standards, sulphur levels in diesel have significantly decreased worldwide over the past 20 years.
The reduction of sulphur content in diesel fuels has improved global air quality (ultra-low sulphur diesel is estimated to have lowered emissions by 90% after it was introduced).
However, the change has not come without its disadvantages, as the removal of sulphur from diesel products created a favourable environment for microbial growth within the fuel.
Why is this an issue?
Microbial corrosion is a blanket term used to define the corrosion of metals through the activity of micro-organisms. Unfortunately the mechanism that causes microbial corrosion is not very well understood due to its complexity and the fact that there is a large range of microbial organisms that can cause it.
A 2012 report found several cases of severe and rapid corrosion in underground diesel tanks thought to be related to microbial corrosion.
Corrosion in Systems Storing and Dispensing Ultra Low Sulfur Diesel, funded by the Clean Diesel Fuel Association (CDFA), was the first proper study to be conducted after increasing reports of a metallic, coffee ground like substance clogging dispenser filters. Corrosion of seals, gaskets, meters and other components of multiple underground storage tanks (UST’s) was also observed.
The study of 6 US sites found that corrosion of metal components in diesel UST’s was common, that the corrosion was not geographically restricted and that microbial corrosion was likely a factor, as indicated by previous studies.
What does this mean for your diesel tank?
Due to limited knowledge of microbial corrosion – and its relation to UST’s in particular – there has been little development of technology to accommodate for or prevent its effects on diesel storage. In fact, there has been no acknowledgment of the existence of microbial corrosion within diesel tanks outside the United States.
Until further studies are conducted to fully understand the cause of corrosion, it is important that site owners and operators are made aware of potential issue through education and outreach programs.
What steps can you take?
Following the 2012 study, the US EPA recommends that site owners visually inspect accessible components of any UST’s storing diesel (including steel and fibreglass tanks) for microbial growth or corrosion as part of their operating procedure, along with regular biocide treatment to kill any existing microbial colonies inside their tanks.
Providing accurate and timely data to your SIR provider will also increase the likelihood of detecting any corrosion in your tank before it’s too late.
Taking these simple precautions can ensure that your diesel storage system remains tight, and help you to avoid significant loss of profit or environmental remediation costs.
Consult your analyst for helpful tips on how to investigate the right way. Get in touch with EMS today.