The hygroscopic nature of biodiesel also means the greater potential presence of water molecules available for microbes to develop and grow. Microbial contamination will increase the risk of injector damage and filter blocking.
Traditionally, storage tank fuel samples are taken and sent to a laboratory for testing. However, regarding microbial contamination, this creates issues as the community of microbes may change during transit if the sample is not stored correctly. It also means a delay in test results.
The Standard Guide for Microbial Contamination in Fuels and Fuel Systems, ASTM D6469 – 14, states in Section 8.5 that: “Samples for microbiological testing should be kept on ice for transport to the laboratory. Tests should be performed within 4 hours and no later than 24 hours after sampling. Samples stored at higher temperatures, or for longer times, can show microbial contamination that does not represent actual fuel system conditions.” Overall, it makes more sense to carry out testing on-site to avoid these issues altogether.