The prospect of biofuels going ‘mainstream’ has drawn more attention to the social impacts of the production and use of transport biofuels. Since 2007, many media stories have appeared about alleged negative impacts of biofuels, notably the price of food going up or land-grab by plantation developers. These stories stand in stark contrast with the rosy picture painted by some academics involved in the technical development of bioethanol or biodiesel. This paper explores the questions when and why negative social impacts are likely to occur and under what circumstances more positive impacts might be expected. These impacts are discussed for three geographically defined biofuel supply chains; north–north, south–north and south–south. These three systems differ in the spatial scale of production and consumption and with that comes a different distribution of environmental, social and economic impacts. In the case of domestic production and consumption in developed countries, the social impacts are relatively minor and can be mitigated by social policies. Large scale, export-oriented production systems in developing countries could theoretically yield positive social impacts, but this would require on the one hand the tailored design of ‘pro-poor’ social innovations and interventions on the ground and on the other hand a certification of the supply chain feeding into consumer demand for ‘ethical’ fuel. The latent existence of this demand might be significant but recent NGO campaigns have severely undermined the ethical credentials of biofuels. It would require a persistent and collaborative effort to restore the brand value of ‘green’ fuel, an effort which will require better legislation and radically improved monitoring and enforcement practices in countries where the very absence of these has led to, and is still causing, the large scale destruction of habitats that are carbon sinks of global importance. The significant levels of government funding for biofuels stand in strong contrast with the problematic environmental and social governance of international biofuels supply chains. Notwithstanding the ‘must tackle climate change’ rhetoric by policy makers and in policy documents, this suggests that biofuels policy may be primarily driven by other concerns, especially regarding energy security. We argue that policies that are designed for a rather narrowly defined purpose of ‘security of supply’, cannot be realistically expected to yield high social or environmental benefits, and certainly not abroad.