It is a vegetable origin fuel that can replace the mineral gasoil.
The ASTM (American Society for Testing and Materials) defines the Biodiesel as “the mono alkyl ester of long chain fatty acids derived of renewable resources, as for example oils vegetables or animal fats, to use them in Diesel motorsâ€.
Its presents in liquid state and it is obtained starting from renewable resources as vegetables oils of soya, colza/canola, sunflower, palm and other, likewise of animal fats, through a process denominated “Ester interchange”.
The ester interchange basically consists on the blendeding of the vegetable or fatty oil with an alcohol (generally Methanol) and an alkali (caustic soda). After a time of rest, the biodiesel is separated by decantation of its by-product Glicerol.
It refers more and more to the alkyl esters of vegetable oils or animal fats and not to the oils or fatty alone, used as fuel in the Diesel motors.