Towards a quantification of the water footprint of biofuels

The objective of this work is to discuss in quantitative terms the water footprint of liquid biofuels for transport. Specific attention is paid to the discussion of the impact of biofuels on water withdrawals for irrigation purposes. Even if this paper addresses mainly the most important components (blue and green water footprint), for a complete assessment, all the stages of the full cycle from agricultural crop/feedstock production to conversion into energy and effluents management (grey water footprint) have to be taken into account. A comparison was performed between the impact on water resources of different types of biofuels feedstock (selected biodiesel and bioethanol first generation pathways from soybean, sugar cane, wheat, rapeseed, sunflower, sugar beet, palm and corn). Four main geographical regions (Europe, US, Brazil and South East Asia) were considered. In addition, energy requirements and corresponding CO2 emissions related to water irrigation and conversion processes were addressed.