Valorization of orange peels in a biorefinery loop: recovery of limonene and production of volatile fatty acids and activated carbon

Abstract Orange peels (OPs) were valorized in a lab-scale biorefinery loop for the recovery of limonene and subsequent production volatile fatty acids (VFAs) activated carbon (AC). Solid/liquid extraction was optimized using n -hexane at 85 °C with an OPs-to-solvent ratio 2:1, allowing yield 1.20% w/w. Then, post-extraction OPs used both VFAs AC. For VFA production, hydraulic retention time (HRT) 5 days total solid (TS) inlet content 10% w/w adopted leading to about 43% gVFAs/gTS. Adsorption tests revealed that, among all matrixes tested, only powdered (PAC) able discriminate no-VFA compounds allowed purification. AC firstly converted into biochar through slow pyrolysis 550 1 h then physically CO 2 880 h. Extraction did not appreciably affect OP properties, while increased (from 43 83%) heating value 17 29 MJ/kg) material. Physical activation its surface area by almost ten times, from 40 326 m /g, proving effectiveness treatment.