Biofuels, Water Footprints, and Green Perspectives

Abstract

Biofuels that are applied using advanced conversion technologies are promoted as green alternative to fossil fuels. The water footprint, the freshwater consumption, linked to current life cycles of such biofuels is much larger than the corresponding consumption associated with fossil fuels. Wind‐ and photovoltaic energy are also characterized by water footprints that are much lower than the corresponding consumption linked to biofuels. Food production and biofuel production increasingly compete for scarce freshwater resources and freshwater stress may increase when biofuel production expands. Availability of freshwater may be a limiting factor in biofuel production. Biofuel life cycles can also be associated with substantial water pollution burdens of nitrate, phosphate, pesticides, and organic substances. On the other hand, it has been proposed to use wastewater for the production of microalgal biofuels. So far, however, no full‐scale production based on this proposal that meets standards achieved by state‐of‐the‐art wastewater treatment facilities has been reported. In many respects relevant to green perspectives, except the consumption of geochemically scarce mineral resources, solar and wind‐based technologies tend to outperform biofuel‐based energy supply technologies. There would seem to be a case for modest expectations as to the share of biofuels that are applied using advanced conversion technologies in future energy supply.