Biodiesel cloud point?

Question

I have done the 3/27 test and it shows my bd is good. I made 5 batches and put a sample of each in the freezer and they all start to cloud at about 55 F. Is this normal?

Answer 1

Remember that biodiesel is basically the same as vegetable oil.  It contains both long and short hydrocarbon chains.  The clouding that you see are the longer chains precipitating out as solids.

You could reheat the oil to remix it, or you could strain out the solid particles so that it can be used in lower temperature environments.  You might also try reheating / remixing it, and then making a 50/50 bio/petrol mixture.  This might have better temperature stability.

My personal choice would be to let it drop to 32° F in a sedimentation tank, and then siphon off the top, leaving the crud behind.  Even in summer, the temperature might drop cold enough for those solids to precipitate and become a problem.  I would avoid using even that bio if the temperature is lower than 50° F.  I think people who mix bio with petrol have much better results though.