Acidophilic nitrification of biogas digestates accelerates sustainable hydroponics by enhancing phosphorus dissolution

Abstract

The low solubility of phosphorus in biogas digestates can cause phosphorus deficiency in hydroponics. We hypothesize acidophilic nitrification could prevent this deficiency by dissolving phosphorus in biogas digestates. Food waste-based biogas digestates were fed into two nitrification systems: an acidophilic reactor (pH 3.27), which was followed by incubation of the withdrawn digestate to increase pH, and a neutrophilic reactor (pH 6.25). The resulting filtrates were used to grow lettuce hydroponically and were compared to a commercial solution. The acidophilic nitrification increased the percentage of dissolved inorganic phosphorus to 73.56 %, while the neutrophilic nitrification ratio was 21.56 %, with NO3-N concentrations of 402 and 617.75 mg L−1, respectively. The acidophilic nitrification resulted in fresh lettuce weight equivalent to the commercial solution, demonstrating that improving phosphorus availability alleviates deficiency. Therefore, acidophilic nitrification will be a pioneering approach to enhance the availability of phosphorus and nitrogen in biogas digestates for hydroponics, promoting resource recycling.