Biodiesel actually has superior lubricity to dino diesel. Adding small amounts of bio to dino diesel (1-2%) can significantly improve lubricity.
It is a very bad idea to use B100 in our cars.
The problem on our cars (with B100) is the use of the DPF and regen cycles. Read this article, which contains a very good explanation of the problem. Note that it was published by an organization that promotes biodiesel, so they don't have a hidden agenda: http://www.biodieselmagazine.com/art...ction-problem/
Note the 2 problems; first, that biodiesel in too high percentages dilutes our engine oil. But - also pay attention to the second problem: that the bio that makes it to the sump interacts with additives and increases the possibility of engine wear.
BMW only warrants our engines for 5-7% bio (depending on the model year), anything beyond that won't be covered by BMW if a problem occurs.