Chapter 6 - Nutrient recycling for sustainable production of algal biofuels

Abstract

Microalgae are an interesting new generation feedstock for the production of biofuels. However, their production costs are currently much higher than fossil fuels, restricting their commercial production. Among the various production processes, the consumption of fertilizers (carbon, nitrogen, phosphorus, etc.) contributes significantly to the total production costs. Moreover, it is projected that the use of industrially manufactured fertilizers will outcome in an unsustainable process, also raising competition between biofuels and food-crops for nutrient availability. To improve the economics and the sustainability of microalgal biofuels, an approach for recycling of nutrients from waste streams should be established, in order to apply nutrients from waste/wastewater at low cost, and to avoid using industrially manufactured fertilizers. For this purpose, a closed-loop production scheme should be developed, in which a series of technologies will be employed in order to obtain the main products (biofuels and other biorefinery products) along with a stream rich in spent nutrients for their reuse for further microalgae cultivation and biomass production.