Biodiesel can be used in stock engines of modern cars with no modification, unlike waste vegtable oil which requires Lovecraft-type modifications.  Older vehicles, like my Mercedes 300D, require replacement of fuel hoses.  Older hoses fail because biodiesel is a solvent that breaks down rubber, but DuPont makes hose called Viton that does not fail.  You can't just go to the local Mercedes mechanic and ask to have Viton installed, which turns out to be a good thing.  You also can't get this hose anywhere, except one internet site, and the Oregon shop associated with it, which also turns out to be a good thing.

I wonder if one of the reasons that 75% of early 1980's 300Ds are still on the road is that they are so easy to work on.  Installation of the Viton hose took about 10 minutes.  The only tool required is scissors.  I bet this fix would cost $85 at your local mechanic, plus you would have to supply the Viton yourself because I bet they will not be carrying it.  Even if you want to use ordinary replacement hose, I would recommend trying to fix this problem yourself.

Viton hose is available at Greaseworks.  They were a pleasure to deal with.