If you need to dispose of it by using it, I would recommend blending it as B5 with real fuel during warm weather only. That shouldn't do any damage and it won't hurt your mileage significantly. Since it's free, it will effectively increase your fuel mileage by a couple of percent.

BTW, is this commercial or homemade BD? If it's homemade, you need to trust that the person who made it knows what he's doing. I probably wouldn't bother with homemade myself.