<p>The industrial circular economy focuses on minimizing waste and maximizes resource efficiency by designing durable, reusable, and recyclable products; reducing costs and environmental impact; and fostering sustainability. Here, the potential of industrial solid and hazardous wastes (ISHWs) mixture as co-firing material with Indonesian coal towards waste-to-energy has been assessed. The study systematically evaluates the blending of ISHWs with coal in various proportions (2, 5, 10 and 20%) to optimize combustion efficiency considering the environmental concerns. The impact of blending on crucial parameters such as fixed carbon content (33.73–35.46% compared to 26.07% for coal), bulk density (0.3–0.4 kg/L, which is similar to that of coal), ash content (9.21–10.38% compared to 9.1% for coal), moisture content (12.04–12.37% compared to 12.4% for coal), volatile matter (43.8–46.31% compared to 43.1% for coal), heavy metal content (35.62–51.81 mg/L against the permissible limit of 2500 mg/L), calorific value (4515.86–5158.78 kcal/kg compared to 5191.1 kcal/kg for coal) and activation energy (46–50 kJ/mol compared to 66–69 kJ/mol for coal) has been elucidated that may affect combustion performance. Various analytical techniques (scanning electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, Brunauer–Emmett–Teller, ion chromatography and inductively coupled plasma, etc.) are implied to derive the physio-chemical properties of ISHW mix, coal and blends of ISHWs in coal. Furthermore, heavy metal content and leaching properties were evaluated and found within acceptable limits. The cost–benefit analysis revealed that blending ISHWs with coal could save 10% to 96% of the current fossil fuel costs while ensuring environmental sustainability.</p> Graphical Abstract <p></p>