The recent cold snap has thrown into focus the varying quality standards of biodiesel and the issues of running fleets on high levels of the eco fuel.
The use of biodiesel is growing as fleets look for cheaper and greener alternatives to traditional fuels.
But not all is going as expected: for example, a bus company in Norfolk had to apologise to customers for “unprecedented disruption” to its services after the biodiesel in all of it 11 buses froze, leaving the vehicles unusable.
First Eastern Counties managing director Peter Iddon said until the problems of using the biodiesel in cold weather are overcome, the bus company will go back to using low-sulphur diesel.
Generally, biodiesel has a slightly higher freezing point than standard diesel.
But, according to the quality of the biodiesel, that freezing point changes.
According to experts at Gloucestershire-based biodiesel producer Green Fuels, biodiesel made from vegetable oil behaves very similarly to standard diesel, freezing at around -12°C.
However, the spokesman said those blends made from ‘tropical oils’ such as palm oil, or fuel made from animal fat, struggle in the northern European climate with a freezing point much nearer to zero degrees.
But due to the number of different production methods, there are very few standards for production of biodiesel.
Only expensive high-end rapeseed oil- based biodiesel has a set European standard – EN 14214.
Fleets running their cars or vans on blends of up to 5% biodiesel mixed with normal diesel have nothing to worry about.