Here is the list of environmental disadvantages of biodiesel:
The cost of biodiesel is one and a half times expensive than the existing petroleum diesel.
It requires lot of energy to produce the biodiesel from soybeans it include the energy of sowing, fertilizing and harvesting.
In some cases it can damage the rubber hoses in the engines especially in the cars that were built before 1994.
Biodiesel has the ability to clean the dirt from the filter but these can get clogged in the fuel filter. But this usually happens when the biodiesel is used in the engine that has been using petroleum diesel for a long time.