Municipal Solid Waste (MSW) is the mixture of many waste types, including organic waste (garden and park waste, food and kitchen waste, paper and cardboard etc.). Such waste creates a living environment for various microorganism species, many of which are known as pathogenic. The presence of microorganisms in favorable conditions (pH, organic matter content, carbon content, moisture, appropriate granulation) leads to decomposing of organic matter, which is accompanied by an increase in temperature. Microorganisms in waste pose a serious risk for staff operating at waste treatment plants. Moreover, heat released by their activity may cause a fire in waste storage facilities. Therefore, it is necessary to search for methods of waste stabilization and hygienization. The most commonly applied technology for waste stabilization is its processing in Mechanical Biological Treatment (MBT) plants. Such treatment is capital – and timeconsuming, however. Waste liming can become an alternative method for stabilization and hygienization of waste. Lime addition is one of the oldest method known by humans for hygienization of certain waste materials, such as animal waste. Currently, liming is applied in sewage sludge treatment as one of the initial operations and is necessary for further sludge management processes. The aim of the research was to valuate temperature changes during mixed MSW hygienization process with CaO addition in the amount of several percent by using a thermographic camera. The reaction of CaO with waste is short and lasts no longer than 20 minutes. The maximal temperatures were reached after 65-124 seconds from the time of CaO addition. The most dynamic increase in temperature were observed up to approx. 120th second of the process, with the rate dependent on the initial moisture of the material. The observed pH values indicate that the maximal dose of CaO additive should not exceed 3%. Such a dose is sufficient for waste to reach pH 12, which, according to literature, guarantees the deactivation of microorganisms.