The answer to your question is yes you can use biodiesel in your furnace. The problem is the cloud point/freeze point is not low enough for winter use in your area. You may be able to use say B20, (20% biodiesel) and the rest fuel oil.
But you have to do a test. Take 20% of B100 and 80% fuel oil and mix and put in your freezer or refrigerator and see how it works, then put in the freezer. Now if your tank is in your basement, should not be a problem is the temp is reasonable in the winter. Again, test the mix you would use.
Biodiesel has a normal storage of about 6 months. Also you need to use a Biocide, yes even in biodiesel. I use FP-60 personally.
I don't think anyone sells it in my area.
It sure is interesting reading about the other guys on here making their own .
I'm not sure if it's worth all the work and trouble collecting the oil for me though.
If you or anyone does use Biodiesel in an oil fired furnace, make sure that the seals in your oil pump are compatable with biodiesel. The same problem will occur with your furnace as it does with vehicles if the seals are not compatable.