Biofuel yield figures are

There are few substitutes for fossil fuels when it comes to keeping the wheels turning on trains, buses, lorries and cars. Biofuels are the obvious alternative, but can we grow enough biofuel crops to meet demand? New research suggests that biofuel-crop yields may have been misrepresented in the past, giving us false hopes about the ability of biofuels to fill the fossil fuel gap.

Until now different biofuel crops have usually been compared by looking at their fuel yield for each unit area. For example it is widely reported that the productivity for each hectare of maize-ethanol is roughly half that of sugarcane. It is a simple way of conveying the complex relationships between the starch, sugar and oil content of different crops, and how they translate to potential fuel yields. However, the way that these yields have been presented is misleading.