Indeed. It has been very much a known issue in the bus world for a while, with that stuff it doesn’t take long for the resulting sludge to build up in the fuel tank and if it gets pumped around the engine, it causes headaches. Biofuel needs treatment and frequent turnover to mitigate the risk.
They will have their work cut out cleaning all of those engines out - even when the systems are flushed, the bug also needs to be killed from all parts of the fuel system that have been exposed to it, or it will be back before long
Often the problem doesn't start in the vehicle fuel tanks, but is imported from a badly maintained static bulk tank.
Clearly this is what happened here, there were far too many problems on the fleet for it to have been a fluke that their tanks all happened to grow microbiological growth and build up sterol glycosides at same time.
Questions need to be asked about the storage conditions of the fuel tanks at Salisbury:
Were they properly sealed to stop water getting in.
Were they flushed or cleaned periodically.
What proceedures were in place to ensure the biofuel and diesel remained mixed (they are marginally different densities and will eventually split with heavier stuff at bottom, same way oil normally floats on water)
Why if they were using biofuels were they still storing it like pure diesel without sufficient extra tank quality checking.
Why was the build up not noticed until point when fuel filters became clogged (did no one notice train filters didn't seem to last as long etc) then suspect the fuel quality.
I always thought the maintenance staff at Salisbury were doing a great job, but this makes it seem like the proverbial couldn't see wood for the trees, as no one could see any build up towards clogged fuel filters.