Sustainable biorefinery development for valorizing all wastes from date palm agroindustry

This study examined how various residues from date palm agroindustrial can be utilized in a biorefinery platform to produce ethanol, methane, and lignin. Liquid hot water, ethanol organosolv, and catalyzed ethanol organosolv (CEO) pretreatments were applied to trunk, leaves, leaf sheath, pedicels, date cake, and seeds. The process included extracting lignin from the liquid fraction, followed by converting the pretreated solid material into ethanol. The fermentation residues were also utilized to produce biomethane through anaerobic digestion. Two different scenarios were employed for the biorefining, i.e., (I) maximum lignin production and (II) maximum biofuel production. The best results for the first scenario were obtained when CEO was employed in the pretreatment of date palm wastes, where 806.9 mL ethanol, 902.8 L methane, and 528.0 g lignin were produced from each kg of each residue. In energetic terms, the biofuel products (i.e., ethanol and methane) were determined to have a combined energy content equivalent to 1553.1 mL of gasoline. Likewise, the most favorable outcomes of the second scenario were obtained by incorporating CEO pretreatment of trunk, leaf sheath, leaves, and pedicels in the valorization of untreated date cake and seeds. Furthermore, for the second scenario, the resulting products were 967.5 mL ethanol, 1605.3 L methane, and 341.0 g lignin, with the biofuel products having a combined energetic content equivalent to 2452.0 mL of gasoline. These findings indicate that the biorefining of date palm agroindustrial wastes has significant potential for bioenergy production.