Research on chestnut residues has shown that phenolic and antioxidant compounds can be extracted. In addition, the waste from the process can serve as a source for biochar production. In this study, three extraction methods were employed. To optimize the extraction process and determine the best experimental conditions, response surface methodologies were applied, including three-level factorial designs (3²) and the Box-Behnken design for each extraction method. Results indicated that the Soxhlet method, distilled water for 4 h, and the 50: 50 distilled water / ethanol mixture for 6 h yielded the most promising results. The highest phenolic content (679. 69 mg GAE/g) was achieved by the Soxhlet method. The residues resulting from the extractions, were mixed and used were used to obtain biochar through the application of fast pyrolysis. Biochar yields were 47 %, and the percentage of ashes and volatiles generated during the process was high.
Cancela et al. (2026) studied this question.