Recycling Nutrients from Anaerobic Digestates for the cultivation of Phaeodactylum tricornutum: A Feasibility study

Abstract The valorisation of Anaerobic digestion waste streams into algal biomass to produce a protein alternative to soybeans could have significant commercial and environmental value. It has the benefit of alleviating the pressure of disposal of nutrient-rich digestate that is rich in nitrogen, phosphorous and trace metals, while potentially reducing the cost of microalgae production. Currently, the use of soybean protein in animal feed has significant negative environmental issues and high carbon footprint associated with its use. This study investigates three types of Anaerobic digestion to grow Phaeodactylum tricornutum Bohlin microalgae. The results found that the crude protein in all concentrations of cow waste and food waste digestates were found to produce a significantly higher concentration of crude protein in comparison to the F/2 control. In addition, cow waste 1% and pig waste 1% formulations were found to have favourable fatty acid profiles, which has significant health benefits in the livestock industry. There was no significant difference in the total fatty acids found in cow waste 1% and pig waste 1% digestates compared to the F/2 control, which was in the range of 243.4 to 269.4 mg/g (dry weight). The other formulations produced a significantly lower (p