Biodiesel is the term to describe alkyl esters which are produced when vegetable oils or animal fats are reacted with alcohol. There are various chemical routes to create biodiesel from bio-oils and fats, but base catalysed transesterification of the oil using alcohol is the most common. Base catalysed is preferred as it involves a single step, which can happen at normal temperatures and pressures, requiring no expensive additives. The use of catalysts such as Sodium or Potassium Hydroxide, produce a mixture of glycerine and biodiesel.
Whilst Biodiesel can be made from any oil-bearing plant matter and other waste oils, certain crops have such a high yield of oil that they have been adopted as the natural biodiesel crops. The Americas, China, and India favour the Soybean, whilst much of Europe have opted for others such oil seed rape and sunflower. In some tropical zones such as peninsular Malaysia, there are extensive plantations of oil palm, while other areas exploit Coconut oil. Waste oils can be processed back into useful biodiesel as can certain types of animal waste.
The great strength of biodiesel as an early player in the sustainable transport industry is the fact that it can be seamlessly integrated into existing infrastructure. Unmodified diesel engines can run on any mix from 10% (B10) to 100% (B100), present tanks and pumping system require little alteration. Various requirements for minimum percentages of biodiesel are now in force across the world, leading to a range of biodiesel mixes being prepared and sold.
The attractiveness of exchanging expensive imported crude oil-derived diesel for home grown carbon neutral biodiesel has meant that as the global prices of crude rise, biodiesel is being adopted simply as a result of its price and availability additional to any ecological credentials that may be recognised.