Biofertilizers from Microalgae

Most chemical fertilizers are finite resources that require large amounts of energy to be either chemically synthesized or mined. Hence, agriculture needs to adopt the concept of circular economy, so that losses are avoided, nutrient recycling is stimulated, and the sustainability of the world food supply is enhanced. Microalgae are a possible solution to this problem, as they are able to uptake N and P present in wastewaters and produce biomass rich in phytohormones and amino acids able to promote plant growth when applied to the soil. To grow microalgal biomass for the industrial production of biofertilizers/biostimulants, raceways and thin-layer reactors are proposed in order to decrease production costs. However, proper control of the composition of the microalgal biomass is crucial, even though this might be difficult to achieve. In spite of this hurdle, preliminary results strongly suggest that microalgae-based biostimulants can significantly impact on plant growth and seed germination indexes when applied to soil with minimal pre-treatment. Moreover, several methodologies have been tested for producing microalgae-based biofertilizers, ranging from preparing water extracts to composting. These technologies to process algal biomass into biofertilizers are discussed.