The article concerns fly ashes generated from the combustion of hard coal and deposited on landfills. Investigation results describing fly ash taken from a combustion waste landfill are presented in the article. The investigation results indicate a possibility for combusting the coal reclaimed by separation from the fly ash and utilizing the remaining fly ash fractions.

In the processes of coal mining, preparation and combustion, the rejects and by-products are generated. These are, among others, the rejects from the coal washing and dry deshaling processes as well as the coal combustion by-products (fly ash and slag). Current legal and industry regulations recommend determining the content of mercury in them. The regulations also define the acceptable content of mercury. The aim of the paper was to determine the mercury content in the rejects derived from the coal cleaning processes as well as in the combustion by-products in respect of their utilization. The mercury content in the representative samples of the rejects derived from the coal washing and dry deshaling processes as well as in the coal combustion by products derived from 8 coal-fired boilers was determined. The mercury content in the rejects from the coal washing process varied from 54 to 245 μg/kg, (the average of 98 μg/kg) and in the rejects from the dry deshaling process it varied from 76 to 310 μg/kg (the average of 148 μg/kg). The mercury content in the fly ash varied from 70 to 1420 μg/kg, (the average of 567 μg/kg) and in the slag it varied from 8 to 58 μg/kg (the average of 21 μg/kg). At the moment, in light of the regulations from the point of view of mercury content in the rejects from the coal preparation processes and in the coal combustion by-products, there are no significant barriers determining the way of their utilization. Nevertheless, in the future, regulations limiting the maximum content of mercury as well as the acceptable amount of leachable mercury may be introduced. Therefore, preparing for this situation by developing other alternative methods of using the rejects and by-products is recommended.

The manuscript presents the condition of circular economy in Poland in diversified approach: subjective (waste streams, energy), sectoral (construction, wastewater treatment, coal energy), related to the resources (phosphorous and anthropogenic minerals) and considering proper energy management (almost zero energy buildings). The achievements reached in different sectors as well as the requirements towards implementation of CE are presented. The advancement of recycling technologies does not deviate from the global level, in terms of areas specific to Poland. Limiting the exploitation of natural resources and usage of new materials as well as producing more durable products are of CE concern. Also energy and heat recovery in buildings and technological processes (e.g. during wastewater treatment), ways of utilization of combustion by-products and water decarbonization waste are described. The implementation of CE in Poland needs not only research and technical activities, but also the modification of technological processes, the right policy, overcoming crosssectoral barriers, developing legal regulations and support schemes for CE.