Microalgae cultivation: nutrient recovery from digestate for producing algae biomass

The aim of this work was to compare the growth rate of algae in mineral medium and in ultrafiltrate medium. The ultrafiltrate allowed us to recover nutrients from a stream of digestate from agroindustrial sources. Two microalgae strains (Phaeodactylum tricornutum and Pavlova lutheri) were cultivated in both of the media. The stream used as growth medium was obtained from an anaerobic digestion plant used to digest mixtures of agro-zootechnical material. The digestate was treated through an ultrafiltration process and then diluted in order to meet the needs of the algae strains. The algae growth on standard medium versus ultrafiltrate medium was similar for both species. Phaeodactylum tricornutum grew in almost 12 days with a similar average productivity on standard medium and ultrafiltrate (respectively of 25 and 24 mg L-1 d(-1)) while Pavlova lutheri grew in 24 days with an average productivity of 15 mg L-1 d(-1) on standard medium and 17 mg L-1 d(-1) on ultrafiltrate. The results show that microalgal biomass production offers real opportunities for addressing issues such nutrient recovery from wastewater streams and CO2 sequestration, and the resulting biomass could be employed as biofertilizer or to produce added-value organic chemicals as new raw materials.