Phosphorus biofertilizer from microalgae

Abstract Phosphorus is a finite nonrenewable resource, a major nutrient for plants, and essential for modern agriculture. Currently, agriculture almost exclusively depends on phosphorus extracted from phosphate rock that is nonuniformly distributed, with large deposits in a few countries. The global food and feed production depend on this finite resource and its socioeconomic impact may well exceed that of fossil fuels. The efficiency of P usage today hardly reaches 20% with the rest ending in wastewater or carried away by runoff from fields to rivers and to the ocean. The phosphorus available in wastewaters is being precipitated, but often in a form that cannot be recycled to agriculture. As an alternative, the potential of microalgae to accumulate large phosphorus quantities may close the cycle from the waste back to agriculture. This is because algae can acquire and store phosphorus through luxury uptake and the phosphorus-enriched algal biomass can be applied as a fertilizer to soil in return. The complementarity of algal biotechnology and agriculture can be further enhanced by synergistic effects achieved if the algal infrastructures are also used for solar-driven recycling of phosphate and other nutrients from wastewater to crop plants. In this chapter, we review the specifics of phosphorus uptake from nutrient-rich waste streams, paying special attention to luxury uptake of this nutrient by microalgal cells and to the potential application of the phosphorus-enriched algal biomass to fertilize crop soils by a delayed release of phosphorus and other nutrients.