One of the methods of waste disposal that offers efficient and economically acceptable solutions is the thermal treatment of waste. Although the method is often disputed by the general public, a significant part of the waste in the world, especially in developed countries with a developed economy, is processed by incineration, co-incineration or some other thermal process. Minimizing the impact of incinerators and co-incinerators on the environment is the main problem of thermal treatment, and particular attention is given to the reduction and treatment of waste products when designing thermal treatment plants. The plants for various thermal treatment procedures and the procedures carried out in them are described and explained in the final paper. The advantages and disadvantages and procedures that minimize emissions of harmful substances are presented. The situation in the Republic of Croatia and the reasons why Croatia lags behind European countries, which have been applying thermal treatment procedures with good ecological and economic results for decades, were criticaly reviewed.