Transformation of food waste. Orange peel (Citrus sinensis) into biochars through sustainable pyrolysis

Food waste represents a biomass source prone of being converted into carbon materials with properties suitable for various applications. In this context, orange peel waste possesses a porous morphology and a surface containing different functional groups (N, O, S), which sparks interest in its valorization. For this reason, the present research proposes the design, synthesis, and characterization of biochars from orange peel (Citrus sinensis) using different pyrolysis conditions for their potential use in the fields of heterogeneous catalysis, energy and agriculture. Firstly, domestic waste orange peels were dried in an oven a milled in a rings mill. Afterwards, different pyrolysis conditions were performed in a muffle, following a green protocol of synthesis. Resulting materials were characterized by several techniques. X-ray Diffraction (XRD) presented typical signals from amorphous carbon at 24°. Fourier-transform Infrared Spectroscopy (FT-IR) showed the presence of different surface functional groups with a decrease in intensities according to the temperature of pyrolysis, due to volatile compounds loss. Consequently, Thermogravimetric Analysis (TG) displayed a decrease in lignocellulose and hemicellulose composition with the temperature of synthesis (from 5% to 2% mass loss). Furthermore, Scanning Electron Microscopy (SEM) showed a granular and porous morphology with a decrease in pore sizes with pyrolysis temperature. Specific surface area (S_BET) analysis is currently in progress. This preliminary study shows that natural structure and composition of orange peel could produce high-performance biochars with tailored properties, converting a domestic waste into a green technological asset.