<p>The non-edible biomass brings attention to energy generation from the agro-residues. The co-pyrolysis of stone apple seed biomass (SAS) and waste X-ray film (WXF) was experimentally investigated. Thermo-gravimetric analyzer (TGA) was employed at varying heating rates (5, 10, 15, and 20 °C/min) to analyze the thermal degradation behavior of the samples. The kinetic parameters and thermal behavior of co-pyrolysis blend were estimated using the Starink, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) iso-conversational models were employed to assess the activation energy (<i>E</i>_α) and thermodynamic properties such as Gibbs energy (ΔG), enthalpy (Δ<i>H</i>), and entropy (Δ<i>S</i>). The average value of <i>E</i>_α when identified through Starink, FWO, and KAS models was estimated to be 211.55, 210.47, and 220.91 kJ/mol, with co-efficient of determination (<i>R</i>²) values of 0.91, 0.91, and 0.90 correspondingly. The average thermodynamic triplet values were estimated to be change in enthalpy (Δ<i>H</i>) = 214.74 kJ/mol, entropy (Δ<i>S</i>) = 32.01 J/mol.K, and Gibbs free energy (Δ<i>G</i>) = 189.74 kJ/mol, respectively. The insight into the kinetic and thermodynamic values reveals that the process is non-spontaneous and indicates the SAS and WXF can be utilized as alternative fuel feedstock owing to their environmentally friendly nature, sustainable energy generation, and ideal characteristics.</p> Graphical abstract <p></p>