The global production of lemons and limes amounts to approximately 16 million tonnes annually, making these fruits among the most significant contributors to global citrus production. The objective of this study was to investigate the potential conversion of citrus waste derived from lemons into functional porous carbon biochar. The results of thermal analysis of the obtained materials provided valuable insights into the carbonization mechanism of the examined raw materials, which offers a sustainable alternative to conventional carbon sources. The physicochemical and thermal properties of the resulting carbon materials were characterized through analysis of phase transformations of carbonates, structural and elemental composition changes resulting from the preceding treatment process, and electrical conductivity. Research demonstrated that the carbonization of the material must be preceded by an oxidation stage, enabling effective reinforcement of the carbon structure. The oxidation process also directly impacts the reduction of other elemental species. Fourier-transform infrared (FTIR) spectroscopy revealed the presence of functional groups that vary in position and intensity depending on the selected process parameters. It was demonstrated that optimal processing conditions encompass preliminary oxidation of the material at 140 °C, followed by carbonization at 700 °C.
Twaróg et al. (2026) studied this question.