Fate of Plant Available Nutrients during Hydrothermal Carbonization of Digestate

Products from the hydrothermal carbonization of two digestates have been analyzed in order to investigate the fate of nitrogen, phosphorus, and potassium in specific plant available speciations. The availability of phosphate and potassium ions was significantly increased due to hydrothermal carbonization of a nutrient-rich digestate. In contrast, the availability of NH4+ and PO43- in the process liquor was decreased to <10% of the original value in the case of a nutrient-poor digestate. With the exception of nitrate, process parameters did not show an influence on the recovery of the investigated ions with the HTC process liquor.