Given the current situation with the high price of oil (an average of $53 per barrel in 2005) and the risk of global warming, the European Union (EU) is reinforcing its objectives related to the production of biofuels: they should account for 5.75% of the overall fuel consumption by 2010 in France, as opposed to 1% in 2005. In keeping with the objective set for 2010, the biodiesel derived from rapeseed is still the preferred biofuel (27.5 million hectolitres projected), compared to the ethanol derived from wheat or sugarbeet (9.3 million hectolitres projected). Our model makes it possible to foresee that there will be a competition between food and energy crops by 2006 and that this will occur even before all of the fallow areas are requisitioned. Our paper stresses the fact that the energy and economic advantages of first-generation biofuels are not sufficient to replace large quantities of petroleum resources.