Biodiesel is basiclly vegetable oil, refined of course,made from something like soybeans or peanuts. To run it in a PSD I think all you would have to do is drain your fuel system completelly and change the filter. Then bleed out your fuel system with the bio.
I don't know where you could get it, but in where I live there is a oil supply company that we can get it from. It costs a few more cents a gallon.
In Ventura county CA, the county gave rebates to all the fishing boats to convert to burning used cooking oil from fast food joints, when you go to the docks sometimes it smells like french fries.