The energy crisis caused by the reduction of fossil fuel reserves, dramatic fluctuations in their price, as well as environmental problems due to global warming, are a challenge to the sustainable development of mankind. Therefore, in recent decades there has been a significant increase in interest in the use of renewable, medium and low temperature energy sources such as solar, geothermal, biomass, marine and ocean heat, and waste heat from various industrial plants and processes, such as petrochemical plants, exhaust gases from gas turbines and internal combustion engines. The organic Rankine cycle (ORC) comes to the fore for the production of mechanical work at lower pressures and temperatures. Micro and small power ORC units for decentralized electricity generation have a special perspective. An important component of any ORC is an expander that can be a volume or turboexpander. In this paper, for a biogas internal combustion engine, the ORC thermal scheme is proposed as a lower cycle in which waste heat is utilized. Due to the importance of the selection of the working fluid as well as the expander for the operation of the ORC, the thermodynamic characteristics of the cycle as well as the thermodynamic and aerodynamic calculation of the ORC turbine were calculated for the five selected organic working fluids. For the ORC turbine which gives the best thermodynamic and aerodynamic characteristics, the profiles of the stator and rotor blades of all stages were designed and the drawing of the longitudinal section of the ORC turbine was made.