Because it is so easy to make, either industrially or domestically in the home garage. Most on this forum source discarded vege oil or buy at the few bio diesel outlets. It is cleaner and better for a diesel motor than dino diesel. The diesel motor was built by Rudolf Diesel and originally run on peanut oil.

Alcohol on the other hand is very dangerous to handle and produce with a low flash point and no visable flame.

Some Oil companies are now adding 5% bio diesel to meet the Ultra Low Sulphur requirements and provide lubrication for the fuel pump. Bio is better for a diesel engine than dino diesel.