Through the use of historical and contemporary satellite images, we developed a novel method for quantifying CO2 emissions from direct and indirect land use change (ILUC) related to the expansion of soy in an area spanning 2.1 million ha in Argentina. The project was commissioned by a leading biofuels producer and has demonstrated a cost-effective alternative to the economic models that have hitherto been applied in the ILUC question. Results have been used to advise on EU policy related to biofuels.