In a world with an increasing population and consequently high demand of resources, new approaches to close material and nutrient cycles are needed. In this perspective microalgae and cyanobacteria present new possibilities.
Humane urine is a nutrient source containing 70% of the phosphorous and 40% of the nitrogen load in household wastewater. The microalgae Chlorella sorokiniana was successfully grown on urine and it was proposed to use the algae biomass as a fertilizer (Tuantet et al., 2014). However, Chlorella’s nutrient requirements does not match the urine’s high phosphorous to nitrogen ratio and due to its rigid cell wall it is difficult to extract energy or functional components from it. Also Cyanobacteria could be used for urine treatment, with the advantage that under certain stress conditions (e.g. phosphorous limitation) some species of cyanobacteria can accumulate a nitrogen rich polypeptide called cyanophycin.