All energy scenarios show a shift toward an increased percentage of renewable energy sources, including biomass. This study gives an overview of water footprints (WFs) of bioenergy from 12 crops that currently contribute the most to global agricultural production: barley, cassava, maize, potato, rapeseed, rice, rye, sorghum, soybean, sugar beet, sugar cane, and wheat. In addition, this study includes jatropha, a suitable energy crop. Since climate and production circumstances differ among regions, calculations have been performed by country. The WF of bioelectricity is smaller than that of biofuels because it is more efficient to use total biomass (e.g., for electricity or heat) than a fraction of the crop (its sugar, starch, or oil content) for biofuel. The WF of bioethanol appears to be smaller than that of biodiesel. For electricity, sugar beet, maize, and sugar cane are the most favorable crops [50 m ³ /gigajoule (GJ)]. Rapeseed and jatropha, typical energy crops, are disadvantageous (400 m ³ /GJ). For ethanol, sugar beet, and potato (60 and 100 m ³ /GJ) are the most advantageous, followed by sugar cane (110 m ³ /GJ); sorghum (400 m ³ /GJ) is the most unfavorable. For biodiesel, soybean and rapeseed show to be the most favorable WF (400 m ³ /GJ); jatropha has an adverse WF (600 m ³ /GJ). When expressed per L, the WF ranges from 1,400 to 20,000 L of water per L of biofuel. If a shift toward a greater contribution of bioenergy to energy supply takes place, the results of this study can be used to select the crops and countries that produce bioenergy in the most water-efficient way.

Agriculture accounts for 92% of the freshwater footprint of humanity; almost one third relates to animal products. In a recent global study, Mekonnen and Hoekstra (2012) [31] show that animal products have a large water footprint (WF) relative to crop products. We use the outcomes of that study to show general trends in the WFs of poultry, pork and beef. We observe three main factors driving the WF of meat: feed conversion efficiencies (feed amount per unit of meat obtained), feed composition and feed origin. Efficiency improves from grazing to mixed to industrial systems, because animals in industrial systems get more concentrated feed, move less, are bred to grow faster and slaughtered younger. This factor contributes to a general decrease in WFs from grazing to mixed to industrial systems. The second factor is feed composition, particularly the ratio of concentrates to roughages, which increases from grazing to mixed to industrial systems. Concentrates have larger WFs than roughages, so that this factor contributes to a WF increase, especially blue and grey WFs, from grazing and mixed to industrial systems. The third factor, the feed origin, is important because water use related to feed crop growing varies across and within regions. The overall resultant WF of meat depends on the relative importance of the three main determining factors. In general, beef has a larger total WF than pork, which in turn has a larger WF than poultry, but the average global blue and grey WFs are similar across the three meat products. When we consider grazing systems, the blue and grey water footprints of poultry and pork are greater than those for beef

Agricultural production is the main consumer of water. Future population growth, income growth, and dietary shifts are expected to increase demand for water. The paper presents a brief review of the water footprint of crop production and the sustainability of the blue water footprint. The estimated global consumptive (green plus blue) water footprint ranges from 5938 to 8508 km³/year. The water footprint is projected to increase by as much as 22% due to climate change and land use change by 2090. Approximately 57% of the global blue water footprint is shown to violate the environmental flow requirements. This calls for action to improve the sustainability of water and protect ecosystems that depend on it. Some of the measures include increasing water productivity, setting benchmarks, setting caps on the water footprint per river basin, shifting the diets to food items with low water requirements, and reducing food waste.