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Mechanochemical-assisted Natural Deep Eutectic Solvent as a platform for an olive leaves biorefinery: Extraction of bioactive compounds and methane production

Year: 2024

Type: article

Abstract: Olive leaves (OL) are a by-product of the olive sector, primarily generated during pruning and olive harvesting. OL is mainly used for livestock feed, composting, or combustion, which wastes valuable compounds. This study proposes a biorefinery process to obtain phenolic compounds, lignocellulosic material, and biomethane from OL. The proposed technique combines mechanochemical extraction with sustainable solvents, such as natural deep eutectic solvents (NADES). NADES are typically formed before the extraction process, but in this study, they were developed and used for extraction simultaneously in a ball mill. Choline chloride (ChCl) was used as a hydrogen bond acceptor with different hydrogen bond donors (oxalic acid (OA), urea (U), fructose (F), water (W), lactic acid (LA), and glycerol (Gl), forming different NADES in the ball mill. A central composite design combined with response surface methodology was employed to optimize the experimental conditions for lignocellulosic material and phenolic compounds extractions. The optimal conditions for maximum extraction of high-value compounds were 0.5 g of OL using 10 mL of ChCl:Gl (3:1) and an extraction time of 1.1 hours in a ball mill. The yields of the recovered lignocellulosic fraction and phenolic compounds were 14.5 ± 2.9 g/kg OL and 1.3 ± 0.3 g gallic acid eq./kg OL, respectively. OL waste generated after the optimized extraction process was evaluated for methane production compared with untreated OL. Similar methane production was observed, with 126 ± 30 mL CH4/g VS for untreated OL and 142 ± 53 mL CH4/g VS for OL waste. These results support the potential of the proposed biorefinery as an environmentally friendly and circular economy approach to recover high-value compounds from OL, with the potential for further improvement

Source: Sustainable Chemistry and Pharmacy

DOI: 10.1016/j.scp.2024.101879