Evaluation of nutrient leaching and algal growth characteristics by anaerobic digestate pellets for marine fertilization

Abstract

In this study, anaerobic digestate pellets that slowly release nutrients into the sea were prepared for the purpose of fertilization of oligotrophic seas and utilization of anaerobic digestate. Three types of digestate (food, sewage, and livestock) and blast furnace cement were used as experimental materials to evaluate the nutrient release function of the digestate pellets and their effect on the growth of microalgae, which are primary producers in the sea. The results of nutrient leaching tests to artificial seawater showed that ammonium and phosphate ions were leached in large amounts from the digestate pellets in the sewage and livestock systems. Microalgae culture tests showed that the addition of digestate pellets from the sewage and livestock systems promoted the growth of the floating microalgae Nannochloropsis.oculata and the attached microalgae Nitzschia sp. These results suggest that digestate pellets may contribute to the fertility of oligotrophic waters.