I've been lucky in that my collections have all been good, liquid oil for quite a long time now.
But I've come across a tin in the stock pile from a one off collection that's fairly thick fat. It'll still pour, (just) at these temperatures but, I started wondering about a different way to handle it without heating, so I tried mixing it with bio.
I tried a 50/50 mix of a small quantity and after a good stir it reached the approximate consistency of good oil. After a few hours of settling a thin layer of bio was evident on the top, but the bulk remained runny.
Probably not the most economical way of handling whites and fat, but, the with a little more experimentation, the idea may help people with no means of heating drums and cubies.
It would be interesting to try a larger scale test using a full tin and a hand drill with a plaster mixing attachment.