Hakea sericea is one of the most aggressive invasive shrubs in Mediterranean ecosystems, producing large quantities of lignocellulosic residues during control operations. This study evaluates thermochemical liquefaction as a valorisation route for this biomass, linking biomass conversion with invasive species management. Whole-plant material was liquefied through acid-catalysed reactions using 2-ethylhexanol as the solvent and p-toluenesulfonic acid as the catalyst. A response surface methodology design was used to assess the effects of temperature, reaction time, and catalyst loading on conversion efficiency. The biomass contained 35.92% cellulose, 32.29% hemicellulose, and 17.36% lignin. Liquefaction yields ranged from 15.59% at 120 °C for 30 min to 82.7% at 160 °C for 90 min, with conversions above 70% achieved within 30 min at higher catalyst concentrations. The regression model explained 87.5% of the variability in liquefaction performance. Spectroscopic and thermal analyses confirmed extensive depolymerisation of lignocellulosic polymers and the formation of an aliphatic-rich bio-oil, with 57.5% of proton signals located in the alkane region of the 1H NMR spectrum. The bio-oil exhibited a higher heating value of 31.91 MJ kg−1, corresponding to an energy recovery of about 85%. Microscopic observations showed strong structural disruption of plant fibres. Overall, the results demonstrate efficient conversion of H. sericea biomass into energy-dense liquid products, supporting its use in invasive species control strategies.
Gonçalves et al. (Wed,) studied this question.