Owing to concerns about energy security and because of increased environmental awareness, the biofuel industry is expanding worldwide. it is therefore extremely important to be able to quantify the sustainability of biofuels in order to determine their benefits over using conventional fossil fuel derived transport fuels. This study investigates the total energy requirement and global warming potential (GWP) of the production of biodiesel from oilseed rape in the UK, using life cycle analyses. Large- and small-scale productions are compared and the sensitivity of these environmental impacts to production variables investigated. Possible changes to the processes are considered, with a view to reduce the energy requirement and global warming potential. This research shows that the scale of the production of biodiesel from oilseed rape in the UK, and the transport involved in the various stages of manufacture, has little effect on its global warming potential. It is also shown that if the rape meal and glycerol were combusted in combined heat and power plants, and the rate of application of nitrogenous fertiliser were reduced from 211 kg/ha to 100 kg/ha, the energy requirement and global warming potential savings from using biodiesel rather than ultra low sulphur diesel would increase dramatically, to 170% and 120%, respectively, on a basis of equivalent net energy content. (c) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.