Developing heat recovery systems to capture and utilize heat from unmanaged dumpsites is crucial for mitigating urban heat island effects and greenhouse gas emissions. Particularly in major cities in Tamil Nadu, the rise in temperatures approaches ignition thresholds. The present study has systematically examined and estimated the heat output across the selected dumpsites in Tamil Nadu, India, specifically Perungudi-Chennai, Vellalore-Coimbatore, and Vendipalayam-Erode open dumpsites. These unmanaged dumpsites hold considerable environmental threats, associated with greenhouse gas emissions and landfill fire risks due to spontaneous ignition, highlighting the urgent need for effective regional waste management strategies. The landfill degradation and transport equations and thermodynamic concepts are utilized to estimate the heat output from the decomposition of municipal solid waste. The stoichiometric equations involved in the anaerobic breakdown process were implemented to determine the liberation of heat per kilogram of the nutrients. It has been shown that carbohydrate breakdown produces the highest heat energy at 2931.17 kJ/kg, followed by lipid and protein decomposition yields of 1840.27 kJ/kg and 1309.74 kJ/kg, respectively. The organic matter percentages by weight in Chennai, Coimbatore, and Erode were 45%, 41.29%, and 64%, respectively, while the carbohydrate percentages were 21.26%, 15.21%, and 15.97%, respectively. The total heat energy liberated by the three dumpsites and the resultant rise in temperature were computed and compared with the spontaneous ignition temperature, which has shown much attention to reducing the risks of fire hazards in Chennai. The present study revealed a close correlation between heat energy generation and carbohydrate content. It has been revealed that issues arising from heat generation can lead to elevated thermal thresholds, risks of landfill fires, and increased air pollution. It has also emphasized that heat generation is a renewable energy source from anaerobic degradation. It underscores the impact of waste segregation practices on heat generation, particularly in densely populated areas.