In order to select the most optimum parameters for running heat recuperation process from aerobic composting process, three testing stages were run involving the registration of the value of recuperated heat volume and the observation of cooling impact on composting process parameters. The values of thermal conductivity coefficient were measured as a function of compost temperature, density and age. The values ranged from 0.171 to 0.300 W/mK. The optimum parameters for process running were selected. Basing on them it was estimated how much heat will be possible to recuperate during the composting process on industrial scale using a battery of heat exchangers. For artificially aerated pile with the following dimensions: lower base 8 m, upper base 5 m, height 3.5 m, length 3 m; it will be possible to recuperate approximately 7.4 kW (from 1 m2 of heat exchanger surface - 774 W).

The present work is devoted to the problem of utilization of the waste heat contained in the exhaust gases having the temperature of 350 °C. Conversion of the waste heat into electricity using a power plant working with organic fluid cycles is considered. Three Organic Rankine Cycle (ORC) power plant solutions are analysed and compared: a solution with the basic, single thermodynamic conversion cycle, one with internal heat recuperation and one with external heat recuperation. It results from the analysis that it is the proper choice of the working fluid evaporation temperature that fundamentally affects the maximum of the ORC plant output power. Application of the internal heat recuperation in the plant basic cycle results in the output power increase of approx. 5%. Addition of the external heat recuperation to the plant basic cycle, in the form of a secondary supercritical ORC power cycle can rise the output power by approx. 2%.

The objective of the project was to find out whether the composting process of municipal waste may be used as a low temperature heat source. It was determined that during high temperature phase of the process on average 930.5 kJ of heat is produced per kg of compost. The designed and made laboratory model was used for carrying out three stages of testing, boiling down to running the composting process with parallel heat recuperation from the process. Basing on the tests, the parameters having affecting the heat recuperation process effectiveness were determined, viz.: optimum initial temperature of cooling water should be approximately 30°C, the reduction of flow rate of the cooling water has advantageous impact on the increase of process efficiency, whereas the safe temperature lower limit for compost cooling should be higher than 52°C (which safeguards compost sanitary purity). It was also observed that in parallel to compost age heat recuperation process efficiency is declining.