These land price differences will influence competitiveness of biofuel production. The key problem is the empirical implementation of this land supply curve for all major regions in the world, as land price data are not available on a global scale. For the EU15 countries, more information on land prices is available, and empirical estimates have been used here (Cixous, 2006). Land heterogeneity is introduced by using a Constant Elasticity of Transformation (CET) function.