Abstract: Abstract: Renewable energy is ever ever-increasing demand for the recycling of biomass wastes. This study aimed to explore the kinetics and potential energy of the agricultural and forestry waste, as well as their fermentation products during pyrolysis. Three types of the biomass wastes—corncob, leaves, and Auricularia dregs—were selected as the raw materials. Their fermented counterparts were prepared for the comparative analysis. Thermogravimetric analysis (TGA) and kinetic studies were conducted to investigate the pyrolysis behavior for the key thermodynamic parameters, including activation energy (E) and pre-exponential factor (A). Additionally, X-ray diffraction (XRD) was employed to analyze the crystal structure and phase composition of the samples. TGA results revealed that there was the a similar pyrolysis of the three materials and their fermentation products. Four weight-loss stages were divided in the pyrolysis. The first stage (30–120 °C) was corresponded to the evaporation of moisture, while the second stage (120–250 °C) was attributed to the decomposition of hemicellulose. The third stage (250–520 °C), the primary weight-loss phase, was associated with the pyrolysis of the cellulose and lignin. The final stage (520–800 °C) was involved the further decomposition of the residual char. Among the samples, the fermented leaves exhibited the lowest activation energy (2.66 kJ/mol), indicating a lower energy barrier for the pyrolysis reaction and higher potential for energy conversion. In contrast, there were the more complex pyrolysis products of the fermented corncob and Auricularia dregs. XRD analysis demonstrated that all samples shared a crystalline structure, with the SiO₂ was identified as the predominant phase. The fermented leaves and Auricularia dregs showed the similar peak positions, indicating the comparable crystal structures. While the fermented corncob exhibited the distinct diffraction patterns. The variations in crystal structure were attributed to the microbial degradation of cellulose, hemicellulose, and lignin during fermentation, which was altered the crystallinity and phase composition of the biomass. Therefore, the fermented leaves were highlighted to serve as a promising feedstock for biomass energy and chemical industries, due to their low activation energy and high conversion efficiency. In contrast, the more complex products were yielded in the pyrolysis of the fermented corncob and Auricularia dregs. A theoretical foundation was provided to understand the pyrolysis kinetics of the biomass waste. The practical guidance was offered for its efficient utilization. The agricultural and forestry waste was transformed into the valuable energy resources. This research was greatly contributed to the sustainable development of economic and ecological fields. In conclusion, the biomass waste can be expected to serve as a renewable energy source. The thermogravimetric analysis, kinetic modeling, and XRD characterization can be integrated to evaluate the pyrolysis behavior and crystal structure of the biomass materials. The fermented leaves can also serve as a high-efficiency feedstock. While the need can also be identified for the further exploration of biomass types. Additionally, the pyrolysis conditions can be optimized to maximize the energy yield for the minimum environmental impact, in order to significantly enhance the scalability of the biomass-based energy systems. Future studies should also focus on the economic feasibility and lifecycle assessment of the biomass-to-energy process for their sustainability and competitiveness in the global energy market. This research can pave the way for the innovative strategies in biomass waste management, in order to promote a circular economy for with the less reliance on fossil fuels.