Biorefinery development and environmental impact assessment using two-phase exhausted olive pomace for the production of succinic acid and phenolic-rich extract

BACKGROUND

This study presents the development of a biorefinery concept using exhausted olive pomace (EOP) for the production of a crude phenolic-rich extract and succinic acid.

RESULTS

The crude phenolic-rich extract was obtained by ultrasound-assisted extraction using 70% (v/v) aqueous ethanol with a phenolic content of 1.22 g gallic acid equivalents (GAE) 100 g⁻¹ EOP (dry basis), an antioxidant capacity of 7.42 μg mL⁻¹ extract (based on DPPH), and an antioxidant activity index of 4.15. Alkaline treatment of the remaining solids with 1% (w/v) NaOH at 90 °C led to 63.9% lignin removal in the liquid fraction, while 87.9% of the initial glucan and 83.4% of the initial xylan remained in the pretreated solids. The hydrolysis efficiency of glucan and xylan corresponded to 42.8% and 42.9%, respectively. Subsequent fermentation with Actinobacillus succinogenes produced 28.1 g L⁻¹ succinic acid with 0.63 g g⁻¹ yield and 0.59 g/(L h) productivity. Life cycle assessment of the biorefinery showed a global warming potential of 0.79 kg CO₂-eq kg⁻¹ dry EOP and an abiotic depletion potential of 14.53 MJ kg⁻¹ dry EOP.

CONCLUSION

The proposed biorefinery could produce 245 g crude phenolic-rich extract and 60 g succinic acid from 1 kg EOP. The remaining solids (136.8 g lignin and 439.9 g post-hydrolysis remaining solids) could be incinerated for energy generation in the olive pomace mill to support the drying of wet olive pomace with up to 10% moisture content. This study demonstrates a sustainable alternative process for the valorization of EOP within an integrated olive pomace mill. © 2025 Society of Chemical Industry (SCI).