Oil Crops as potential sources of biofuels

For many thousands of years, oil crops have been used as sources of a wide range of edible and non-edible products, including fuels. However, during the twentieth century, their use as fuels became very limited as they were largely replaced by fossil fuels. This situation has changed dramatically over the past decade with mounting pressure to limit CO2 emissions from, and to reduce dependence on, fossil fuels. As a result, there has been a huge growth of interest in the use of plant-derived oils as renewable alternative fuels such as biodiesel. At present, the major globally traded sources of biodiesel are mainstream commodity oil crops, principally oil palm, soybean, and rapeseed. Other minor oil crops serve mainly as local sources of biodiesel. Although evidence can be conflicting, data from life-cycle analysis (LCA) studies tend to support biodiesel, especially tropical biodiesel crops, as having more favourable net carbon/energy balances than most bioethanol crops. Research is now focussing on ways to improve the balance sheet of biodiesel crops even further by increasing their yield and manipulating fatty acid composition. New tropical biofuel crops such as jatropha are also being developed and, while the yields of some current varieties have been disappointing, there are good prospects for further improvements over the next decade. In the longer term, the so-called “next generation” biofuel crops such as oil-producing or hydrogenproducing microalgae, or even non-carbon alternatives such as wind or solar power, may eventually largely replace conventional oil crops as sources of renewable fuel. This will enable oil crops to act as renewable sources of hydrocarbons, e.g. for manufacture of plastics, long after fossil sources are depleted.