Thermochemical valorization of biomass into sustainable biomaterials and biofuels: The potential of AAEMs rich mediterranean wastes

Mediterranean biomass presents distinctive features compared to the Northern lignocellulosic biomasses, which are typically exploited for thermochemical conversion. The present work addresses slow pyrolysis and co-pyrolysis of three biomass largely available in the Mediterranean regions, namely cactus cladodes (CC), pomegranate peels (PGP) and pine cones (PC) in a fixed bed batch. Notably, CC, is characterized by a large content of ashes (˃20 %), and is particularly rich in alkali and alkaline-earth metals (AAEMs), which, upon co-pyrolysis, could act as catalysts and affect the chemical composition of the bio-oil, as well as the properties and yields of the biochar. The results indicated that co-pyrolysis decreases the gas yield and increases the bio-oil and biochar yields. The bio-oils produced from either PGP or PC are complex mixtures of chemicals, including phenols, aromatics, aliphatics and anhydrosugars. Co-pyrolysis of PC with CC increases the content of phenol and aromatics in the bio-oil, while decreases the content of retene derivatives. Co-pyrolysis of PGP with CC increases the content of phenols and reduces that of furfural and anhydrosugars. The biochars produced from co-pyrolysis of CC with either PGP or PC have low O/C and H/C ratios, high alkalinity and large content of Ca, K, Mg and P