Hydrochar prepared from aquatic and terrestrial biomass: Comparative analysis of characteristics and applications

The benefits of hydrothermal carbonization (HTC) for carbon sequestration, energy, and soil remediation are widely recognized. Up to the present, there has been much research on hydrochar from terrestrial biomass residues, but there is little research on hydrochar based on aquatic plants. In this study, the physical and chemical properties of water hyacinth (representative of aquatic plants) and corn stalk (representative of terrestrial plants) were systematically analyzed under the condition of single hydrothermal carbonization. The results showed that water hyacinth-based hydrochar (WHHC) had well-developed pores, rich functional groups, and high nitrogen content. Among them, the nitrogen content of WHHC was 3.83%, which was more than three times the nitrogen content of corn straw-based hydrothermal carbon (CSHC) (1.11%), and the number of micropores, mesoporous pores, and macropores were also higher than that of CSHC. These differences were attributed to the contrasting growing environments and main components of water hyacinth and corn stalk. These differences revealed their potential application directions: WHHC can be used as an adsorbent and soil amendment; CSHC is more suitable as a supplementary energy source because of its higher carbon content and stability.