Identification of Aromatic Phytochemicals from Sustainable Horticulture Waste via scCO 2 Extraction: A Comparative Study

Climate change, resource constraints, and increasingly fragile global supply chains are reshaping how chemicals, materials, and fragrances must be produced; placing sustainability at the centre of future industrial viability. Despite this, horticultural waste streams such as rejected and surplus flowers remain under-utilised despite their rich phytochemical content. This study explores the valorisation of discarded Hyacinthus orientalis flowers through the selective recovery of aromatic compounds using supercritical carbon dioxide (scCO 2) extraction, a green, and advanced chemical separation technology. Volatile profiles were first characterised by solid-phase microextraction and GC-MS, revealing colour-dependent differences in aroma composition and identifying phenylethyl alcohol (PEA) as a key floral compound. A fractional factorial Design of Experiments was employed to assess the effects of pressure, temperature, CO 2 flow rate, and extraction time. Pressure emerged as the dominant factor influencing both extract yield and PEA concentration, while extraction kinetics demonstrated rapid initial solute recovery followed by diffusion-limited behaviour. Supercritical CO 2 extraction produced extracts enriched in delicate floral volatiles while mostly excluding non-volatile lipids, waxes, and thermally degraded compounds common with solvent-based and distillation techniques. Importantly, scCO 2 enabled direct extraction from fresh flower biomass, eliminating energy-intensive drying and pre-treatment steps. This reduces environmental impact and operational costs while preserving delicate phytochemicals. Overall, the results demonstrate a viable pathway for transforming low-value horticultural waste into high-value aromatic ingredients, supporting circular economy principles, and resilient production.