Perspectives on novel food packaging applications of hydrochar generated during the hydrothermal synthesis of carbon dots

Hydrochar, a carbon-rich byproduct produced during the synthesis of carbon dots via hydrothermal carbonization of biomass, has received limited attention despite its promising properties. Hydrochar, produced via hydrothermal synthesis, is characterized by tunable surface chemistry, diverse functional groups, and a lower energy requirement for synthesis than its analog, biochar, produced by the dry pyrolysis process. While biochar has been extensively studied for its advanced functionality in food packaging, hydrochar has not been fully explored. Hydrochar exhibits superior surface chemistry compared to biochar, enabling it to interact effectively with biopolymer matrices, which results in enhanced mechanical strength, improved thermal properties, and potential antioxidant and antimicrobial activities. This pioneer review aims to draw parallels between analogous biochar-based packaging systems and provide a pioneering perspective on how hydrochar can be utilized to develop active and intelligent packaging solutions. Moreover, the simultaneous use of both hydrothermal synthesis products, i.e., carbon dots and hydrochar, has been highlighted, which supports a zero-waste approach aligned with the goals of the circular economy and sustainable development strategies.