The aim was to extract free phenolics using a green solvent (ethanol), and bound phenolics from glabrous canary seed hulls. The efficiency of ethanol 75% was compared with that of other solvents used in the literature (acetone 70%; methanol 80%) in terms of phenolic yield and antioxidant activity. Bound phenolics were extracted with ethyl acetate, prior to hydrolysis with NaOH 2 M. The phenolic extracts obtained were characterized according to extraction yield, total phenols, flavonoides, antioxidant activity, radical DPPH; and phenolic profile, HPLC. Methanol 80% had lower extraction yield, and acetone 70% had lower antioxidant activity; whereas ethanol 75% was the most efficient solvent to obtain free phenolics. Extraction yield of bound phenolics (6411.13 mg/100g hulls d.b.) doubled the value of free phenolics. Thus, antioxidant activity was four times higher (78.67% inhibition of radical DPPH). On the other hand, phenolic acids predominated over flavonoids compounds in a rate 26/1. Ferulic acid was the dominant (42.48 mg/100g hulls), followed by p-coumaric (39.07 mg/100g hulls). Although the use of glabrous canary seed is new, interest in its processing at industrial level makes canary seed hulls a potential waste material that could be leveraged as a source of bioactive compounds with several applications.

Sunflower hulls are an abundant lignocellulosic waste with significant but underexploited potential for the recovery of high-value compounds and production of renewable energy. In this study, an integrated biorefinery approach was developed for the sequential recovery of waxes, free and bound phenolic compounds, and biomethane. Three pretreatment strategies (acid-thermal, mechanically assisted alkaline, and ultrasound-assisted ethanolic) were comparatively evaluated to determine their effects on bound phenolics extraction and biomethane production. Sequential extraction recovered 0.94 g of waxes 100 g⁻¹ d.b. and 145.52 mg GAE 100 g⁻¹ d.b. of free phenolics, with chlorogenic acid as the predominant compound. The different pretreatments exhibited contrasting performances depending on the valorisation criterion considered. Although acid–thermal pretreatment achieved the highest recovery of bound phenolic compounds (99.3 mg GAE 100 g⁻¹ d.b.), ultrasound-assisted ethanolic pretreatment preserved the largest proportion of the original biomass and resulted in the highest overall methane recovery (150% relative to the untreated biomass). Each pretreatment modified the lignocellulosic matrix through hemicellulose solubilization, lignin disruption, and fibre reorganisation, thus explaining the observed differences in phenolic release and biomethane production. The results demonstrate that each pretreatment favours a specific product stream, and that the selection of the most suitable pretreatment depends on the biorefinery’s objective.