The final thesis describes the work of CHP biomass plants. We can see which raw materials are used for fuel, what kind of technology is used for combustion of selected raw materials and the difference between cogeneration power plants and power plants used for electricity generation. Furthermore , the operation of the powerplant is explaind, where is shown process of gathering the raw materials to the creation of electricity and heat. There is still a lot of processes that occur prior to obtaining the desired energy and they have a major role in the operation of power plants and they are all described in the third chapter. Finally we get the electrical energy via a generator and it is then used in the timber industry complex, it is used to start the engine inside the plant and the rest is sent to the network.