Carrot green, the algae Chlorella pyrenoidosa, and straw as representatives for different types of biomass are converted by hydrothermal conversion. The amount of nitrogen remaining in the hydrochar as well as in the aqueous phase is determined, and the amount of nitrate, nitrite, and ammonia in the process water is analyzed. The nitrogen content of hydrochar has an significant impact on the properties of hydrochar; therefore, a control of the nitrogen content would be useful to design hydrochar for different applications. With regard to the fate of nitrogen, the different biomass feedstocks show significant differences as a result of the different chemical nature of nitrogen compounds in the feedstock. A complete removal of nitrogen from the hydrochar could not be achieved. In contrast, wood incorporates nitrogen when impregnated with the amino acid cysteine during hydrothermal carbonization.

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