Pyrolytic evaluation of essential oil industry waste: Effect of pyrolysis temperature on bio-oil composition

The essential oil industry, a rapidly growing sector driven by its value-added applications, generates substantial amount of waste that contribute to land pollution and open dumping, highlighting the urgent need for effective waste management strategies. In this study, spent carrot seed waste (SCSW), a common byproduct of the essential oil industry, was pyrolytically evaluated at various temperatures (300-500 °C) to produce bio-oil. The proximate analysis of SCSW showed high volatile matter 71 % along with high ash content 13 %. XRF analysis of SCSW revealed the presence of alkali, alkaline and transition metals, which can act as an inherent catalytic site for the breaking of larger bio-oil compounds. SCSW contains substantial amounts of cellulose (32 %), hemicellulose (28 %) and lignin (27 %) along with extractives (12 %). TGA and DTG analysis exhibited the active devolatilization zone between 250 and 500 °C with weight loss of 50 %. Upon subjecting SCSW to pyrolysis at various temperature, the maximum amount of bio-oil was obtained i.e., 16 wt% at 500 °C. The GC-MS analysis revealed that notable amounts of cyclic ketones (42-50 %) were present in the SCSW-bio-oils, formed under the influence of metallic sites in the SCSW. These cyclic ketones mainly 1,3-Cyclopentanedione, holds the potential to be used for drug development and chemical probes applications. Increase in pyrolysis temperatures showed significant reduction in hydroxy-ketones and furanics but in contrast, there is the significant increment in cyclic hydrocarbons and anhydrosugars in the bio-oil. NMR analysis revealed highest aliphatic, aromatic and carbohydrate nature at 500 °C.