Once ratified the Kyoto protocol, Spain arises the great challenge of reducing the emissions of greenhouse gases. Among the measures proposed is the introduction of biofuels in the market, both for the transport sector and for the production of heat. This paper compares the environmental impact from the production of biofuels whose origin is the oil obtained from sunflower, rapeseed and soybeans. The environmental impact of each production is performed by applying the methodology of life cycle analysis (LCA). The categories where you get a greater impact are land use, fossil fuels, carcinogens, inorganic respiratory and climate change. The cause is mainly due to the processes of seed production. We have also found a significant impact on the drying and preparation processes of the seed as well as the crude soybean oil extracting process. Moreover as the LCA shows production of rapeseed and sunflower has a positive contribution to climate change. (C) 2010 Elsevier B.V. All rights reserved.