ABSTRACT Common waste biomasses such as fruit and vegetable peels and spent coffee grounds are valorized via low‐temperature pyrolysis (400°C) to produce valuable biochar and bio‐oil for diverse downstream applications. Detailed and comprehensive characterization of the resulting biochar, including carbonization degree, morphology, surface acidity/basicity, and energy content, enables the assessment of their suitability for technological and environmental uses, based on the specific properties developed during thermal conversion. The bio‐oils exhibit feedstock‐dependent chemical profiles enriched in platform chemicals (e.g., HMF, furfural, cyclic ketones), lipid‐derived compounds, and aromatics, supporting their targeted utilization in energy, materials, and chemical synthesis. Upon sulfonation, selected biochars display promising properties as acidic heterogeneous catalysts (1.65–1.75 mmol H + g −1 ), showing high activity in industrially relevant reactions such as esterification and condensation. Their application in the cross‐aldol condensation between bio‐based cyclopentanone and cyclohexanone, targeting sustainable aviation fuel (SAF) precursors (C 10 ‐C 18 cyclic compounds), is explored in detail. Among all samples, sulfonated biochar derived from coffee grounds and orange peel achieves superior catalytic performance, matching or surpassing commercial Amberlyst‐15 under mild conditions (120°C, 4 h, atmospheric pressure). Catalyst stability and recyclability tests confirm performance retention after regeneration, with surface deactivation by heavy compounds deposition being fully reversible.
Schiaroli et al. (Fri,) studied this question.