Pyrolysis Valorization of Vegetable Wastes: Thermal, Kinetic, Thermodynamics, and Pyrogas Analyses

Abstract

In comparison to other methods, valorising food waste through pyrolysis appears to be the most promising because it is environmentally friendly, fast, and has a low infrastructure footprint. On the other hand, understanding the pyrolytic kinetic behaviour of feedstocks is critical to the design of pyrolysers. As a result, the pyrolytic degradation of some common kitchen vegetable waste, such as tomato, cucumber, carrot, and their blend, has been investigated in this study using a thermogravimetric analyser. The most prevalent model fitting method, Coats–Redfern, was used for the kinetic analysis, and the various mechanisms have been investigated. Some high-quality fitting mechanisms were identified and used to estimate the thermodynamic properties. As the generation of pyrolysis gases for chemical/energy production is important to the overall process applicability, TGA-coupled mass spectrometry was used to analyse the pyrogas for individual and blend samples. By comparing the devolatilization properties of the blend with single feedstocks, the presence of chemical interactions/synergistic effects between the vegetable samples in the blend was validated. The model, based on a first-order reaction mechanism, was found to be the best-fitting model for predicting the pyrolysis kinetics. The calculated thermodynamic properties (ΔH (enthalpy change ≈ E (activation energy))) demonstrated that pyrolysis of the chosen feedstocks is technically feasible. According to the TGA–MS analysis, blending had a considerable impact on the pyrogas, resulting in CO2 composition reductions of 17.10%, 9.11%, and 16.79%, respectively, in the cases of tomato, cucumber, and carrot. Overall, this study demonstrates the viability of the pyrolysis of kitchen vegetable waste as a waste management alternative, as well as an effective and sustainable source of pyrogas.