The water footprint of biofuels from microalgae

Microalgae are receiving much interest as a possible biofuels feedstock, resulting in increasing research and development efforts. Biofuels from microalgae are potentially important sources of liquid renewable energy carriers, replacing petrol. Algae are not produced on a large-scale yet, but research shows promising results. Biofuel production needs water, an increasingly scarce resource. The interest in biofuels, in combination with an increasing global water scarcity, causes a need for knowledge of the water footprint (WF) of this new energy resource. This chapter gives an indication of the water footprint (WF) of algae-based biofuels. It uses the WF method as an indicator of water use. We aim to give an overview of the methods used for the cultivation, harvesting and conversion to biofuels of microalgae and the related WF. The results from our case study for microalgal biodiesel produced in California, USA, show a blue WF between 16 and 172 m 3 /GJ and a grey WF of 0. The results, however, show large variation and depend on the water recycling during the harvest and dewatering process. Compared to biofuels from crops, the green and grey WFs of biofuels of microalgae are favorable, but blue WFs might be larger in some cases. There is a need to assess the impact of the microalgae biofuels production on fresh water resources, because fresh water of adequate quality is an important criterion for assessing the physical, economic and environmental viability of energy systems.