The seeds of green energy: Expanding the contribution of plant oils as biofuels

Plant oils represent one of the most energyrich sources of renewable fuels available in Nature. Most of these oils occur in the form of triacylglycerols (TAGs) that can be transformed into biodiesel by conversion of their acyl chains into fatty acid methyl esters. In 2009, 14 billion litres of biodiesel were produced worldwide from plant oils (largely in the EU). This compares with 70 billion litres of ethanol (largely from Brazil and the USA). Both of these fuels now depend on land and crops (e.g. oil seeds, palm trees, maize and sugar cane) that are also used for foods. To meet growing demand and avoid competition with food, major expansion of biofuel production and development of new sources of biofuel are required. In this article, we outline how plants synthesize oils and describe some ways in which supplies of oils from plants could be increased to provide a larger contribution to renewable energy supplies.