Kinetic analysis and pyrolysis behavior of organic fraction of municipal solid waste towards the production of renewable fuel: A sustainable approach to resource recovery for circular economy

Valorization of organic fraction of municipal solid waste (OF-MSW) for bioenergy production is a widely adopted approach. In view of the requirements for scaling up, optimization and design of the pyrolysis reactor, the kinetic and thermodynamic behavior, reaction mechanism along with product characterization has rarely been explored. In the present study, physicochemical analyses, kinetic, and thermodynamic study of OF-MSW were performed using TGA thermograms obtained at four heating rates (5, 10, 20, and 40 °C min⁻¹) under nitrogen atmosphere. Model-free methods, viz Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), and Friedman (FRD) models were employed to determine the mean activation energies (E_o), which were found to be 153.84, 155.48 and 159.41 kJ mol⁻¹ respectively. These values are consistent with those calculated by the combined kinetic (CK) model. The pyrolysis mechanisms based on the CK model involve a single-step process and can be represented as f(α)=(1-α)^1.50075α^−1.0606. The frequency factor, ΔG, ΔH, and ΔS using FRD model were found to be 3×10¹² s⁻¹, 164.82 kJ/mol, 155.46 kJ/mol and -32.74 J mol⁻¹ K⁻¹ respectively. Additionally, Criado method with Y(α) master plots were employed to elucidate the reaction mechanism. It was observed that at the initial conversion stage, second order and first order reaction mechanisms were predominant followed by D3 (three-dimensional diffusion) at higher conversion. The bio-oil and biochar obtained were further characterized in terms of physico-chemical and spectroscopic techniques to explore its potential in environmental and energy applications. By embracing the circular economy concept, we can transform OF-MSW from a linear “take-make-dispose” into valuable resource stream.