Strategic way for peach seed valorisation by integrating thermochemical approaches: Transesterification and pyrolysis

This study aimed to maximise carbon utilisation in the biodiesel (BD) production from transesterification of oil-bearing seed and subsequent pyrolytic valorisation of defatted biomass waste. Peach seed (PS) was selected as a model for the oil-bearing seed. After extracting PS oil (PSO) (56.3 wt% of PS), the defatted PS (DPS) was subjected to CO₂-assisted pyrolysis over a nickel catalyst, resulting in enhanced conversion of DPS into syngas, particularly CO. The homogeneous reaction between CO₂ and VM liberated from DPS led to reduced CO₂ formation and its oxidation with VM, resulting in enhanced CO evolution. Compared with pyrolysis under inert N₂ conditions, syngas production increased by 39.0 % in the presence of CO₂. PSO was converted into BD via thermally induced transesterification, yielding superior BD yield compared to alkali-catalysed conversion. Indeed, the BD yield from thermally induced transesterification was 98.15 wt%, whereas the BD yield from alkali-catalysed transesterification was 87.10 wt%. To further enhance the transesterification kinetics, biochar produced from the pyrolysis of DPS served as a catalyst. This approach resulted in a BD yield of 98.34 wt% at 340 ˚C. CO₂ mitigation potential was evaluated by integrating the pyrolysis of DPS with the BD production process from PSO.