INVESTIGATION OF CO-PYROLYSIS OF FISH WASTE AND EMPTY FRUIT BUNCH: KINETIC AND THERMODYNAMIC PARAMETER ESTIMATION, PRODUCT YIELDS, AND BIOCHAR CHARACTERISATION

Abstract

This study explores the feasibility of utilising fish waste (FW) and empty fruit bunches (EFB) as feedstocks in co-pyrolysis. The research aims to optimize copyrolysis by estimating kinetic and thermodynamic parameters, evaluating product yields at various temperatures, and characterising biochar properties. Thermogravimetric analysis was employed at heating rates of 10, 20, and 30 °C/min, while kinetic and thermodynamic parameters were estimated using the Kissinger- Akahira-Sunose and Flynn-Wall-Ozawa methods. Reaction mechanisms were inferred using Criado plots. Product yields were measured in a tube furnace at 500 - 600 °C temperatures. The biochar was characterised using Fourier-transform infrared spectroscopy and scanning electron microscopy. Results revealed that activation energies (𝐸!) ranged from 25.56 to 170.76 kJ/mol, with 75FW:25EFB exhibiting the lowest 𝐸!. The complexity of co-pyrolysis reactions was evidenced by frequency factors with average values spanning from 1.65 x 108 to 5.66 x 1011 s-1. Reaction models identified included Power law, Avrami-Erofeev, Reaction-order, Geometrical contraction, and Diffusion models. The changes in enthalpy and entropy analyses highlighted the energy-intensive and thermodynamic equilibrium tendencies of the process, with the change in Gibbs free energy confirming the feasibility of copyrolysis. FW-rich mixtures produced higher biochar yields, attributed to their ash content, while EFB-rich mixtures favored biogas production due to higher volatile content. At 500 °C, 75FW:25EFB achieved 47 % biochar yield, which decreased to 42 % at 600 °C. EFB demonstrated superior gas production potential, reaching 67 % biogas yield at 600 °C. Co-pyrolysis resulted in improved liquid fuel and gas yields compared to individual feedstocks. Biochar analysis revealed that FW-rich biochar contained nitrogenous and aromatic functional groups, while lignocellulosic structures characterized EFB-rich biochar. Co-pyrolyzed biochar also showed enhanced carbonization, porosity, and functionality, making it ideal for soil amendment, water filtration, and renewable energy uses. The study highlights the advantages of optimizing FW and EFB ratios, with 75FW:25EFB and 50FW:50EFB emerging as the most effective blends for balanced product yields and biochar quality. This research demonstrates the potential of FW and EFB co-pyrolysis as a sustainable approach to optimize biochar production and convert waste into valuable resources.