Biorefining of pine cone forest waste: Ultrasound assisted extraction followed with thermal degradation for a zero waste process

Abstract

Pine cones tend to form a high amount of waste in the Himalayan region of India that is covered with dense pine forests. It is therefore important to develop an economical biorefinary model for utilisation of pine cone waste towards sustainable circular economy. In the current study ultrasound assisted extraction (UAE) followed by pyrolysis was studied and optimised for extracting maximum value added products from waste pine cones. In UAE parameters like soild-to-solvent ratio, temperature and ultrasound power was studied and optimised. The UAE was also compared with maceration and soxhelt extraction. The solid pine cone powder were characterised using scanning electron microscopy before and after extraction. The chemical analysis of extract showed a compositional change in ultrasound as compared to maceration. Peleg’s mathematical model was used for describing the extraction kinetics and to calculate the initial rate constant and equilibrium concentration for all investigational results. The activation energy of ultrasound extraction was 48.23 kJ mol⁻¹. The thermal degradation of the solid biomass after extraction was studied using thermogravimetric analyser. The results do not show any significant difference in the volatile matter content of the biomass before and after extraction using ultrasound or maceration. The treatment tends to enhance the volatile matter content of the pinecones. The char residue may be further used for soil enhancement applications leading to a sustainable zero waste process.