The aim of this master`s thesis was to clarify the utilization potential and different treatment possibilities of bottom ashes derived from municipal solid waste incinerator of Kotka Energy Ltd. Alternatives in utilization were different kind of earth constructions and covering landfills. In addition, disposal of bottom ashes to landfills was investigated as an alternative for utilization. Using treated bottom ashes in earth constructions or as a covering material in landfills as well as disposal in the landfills, is controlled by law. Council of State has defined leaching limits of heavy metal ions for bottom ashes going to be disposed to landfills. It is decided within these limits whether the bottom ashes are managed as non-hazardous waste, inert waste or hazardous waste. If bottom ashes are used as a covering material in landfills, it also needs to qualify the limits for the leaching of heavy metals ions in that type of landfill. When using bottom ashes in earth constructions, the limits are defined by The Decree of Earth Constructions. Where ever bottom ashes are used, it always requires an environmental permit according to The Environmental Protection Act. From analyses that have been done to bottom ashes from the incineration plant of Kotka Energy Ltd, it seems to be possible to use threatened bottom ashes for example in structures of fields and landfills and also as a covering material in the landfills. Exploiting bottom ashes in earth constructions concerning district heating system, needs more investigation because of the risk of possible corrosion in district heating pipes. As a result of this master`s thesis was developed an operational model. With the help of this model it is possible to minimize the costs when processing, utilizating and disposing the bottom ashes derived from incineration plant of Kotka Energy Ltd.