The main purpose of this paper was to outline a novel approach for the use of industrial by-products generated in coal mines and coal-fired power plants as the components for artificial soils. Several coal combustion by-products, coal mine waste and organic waste materials were tested at laboratory scale for use in the reclamation of areas degraded by coal mining activity. The role of artificial soils was the land rehabilitation of the high acidic waste heap. The results revealed that the amounts of organic matter (14.87–25.01%) and nutrients in the soil substitutes were sufficient to support plant growth, i.e., N (0.37–0.51%), P (0.23–0.47%), K (1.78–3.17%), Ca (4.93–8.39%) and Mg (1.16–1.71%). A phytotoxicity test using white mustard (Sinapis alba) seeds under laboratory conditions showed good germination results (56–66%) for three soil substitutes that did not contain fly ash from biomass combustion, compared to the reference soil (84%). The relationships established for the aqueous leachate parameters of soil substitutes vs. the Sinapis alba germination revealed negative correlations with electrical conductivity (r = −0.88), SO₄²⁻ (r = −0.91) and Cl⁻ (r = −0.70) ions; the two latter ones were responsible for the salinity which hampered the germination process of the soil substitutes. Moreover, quite similar correlations were obtained between the germination of Sinapis alba and the trace elements of the soil substitutes: Fe (r = −0.69), Cd (r = −0.72), Cu (r = −0.80), Pb (r = −0.78) and Zn (r = −0.74). However, negative and significant correlations in aqueous leachates were shown only with Ni concentration (r = −0.73). The relevance of these results for the effect of salinity on germination and the early growth of S. alba was discussed in detail and was confirmed with the Principal Component Analysis (PCA). The study proved that the physicochemical characteristic of recycled wastes exhibited their potential usefulness for the reclamation of affected areas such as mine waste heaps.

Coal mining and the energy industry generate large amounts of solid waste, which must be disposed of in landfills and lead to numerous environmental problems. This paper presents a method for creating artificial soil mixtures based on an EU-funded international research project called RECOVERY. The main idea behind the proposed solution is the safe use of coal combustion by-products (energetic slag and decarbonation lime), mining waste (aggregate and sealing material) and spent mushroom compost as components for creating artificial soils. Laboratory tests of the soil substitutes showed low concentrations of heavy metals and high macronutrient content, adequate for proper plant growth. As a result of a two-year study on the application of soil cover on a 4000 m² testing ground, species characteristics for the mesotrophic, dry meadow, ruderal and segregated vegetation were found. In the second year of the in situ study, an apparent reduction in soil salinity was observed. The principal component analysis confirmed that decreasing soil salinity positively affected ruderal and dry meadow species. In contrast, high salinity levels showed no adverse effect on mesotrophic meadow vegetation. The results demonstrated that applying soil covers elaborated from industrial by-products is valuable for recovering high-acidity coal mine waste heaps.

Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe₂O₃) compared to the historical slags (up to 26.1 wt% of Fe₂O₃). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management.

This paper presents the results of research on the possibility to obtain CRMs (REEs) and industrial metals (Zn) from slag as a waste generated as part of zinc and lead extraction processes. Physicochemical methods were used to separate CRM and Zn concentrates: magnetic separation, sintering with NaOH and leaching with selected mineral acids. After analysing the obtained results, it was found that the use of concentrated hydrochloric acid and a temperature of 363 K for leaching was effective in separating REEs from slags obtained from current production. The recovery rate in this case ranged from 83.73% for La to 98.03% for Eu. For slag samples (M1) obtained from current production from ZGH Bolesław S.A.(Poland) as well as HC Miasteczko Śląskie S.A. (Poland) and treated with concentrated HCl, the leaching level of Bi, Zn, Ni, Mn and P exceeded 90% compared to the content in the reference sample. For a historical slag sample from Ruda Śląska (Poland), treatment with concentrated HCl yielded a high leaching level of Cd (70.90%), Pb (78.66%), As (72.49%) and Mo (61.90%). A concentrate containing 1.64% of REEs and 67.1% of Zn was isolated from the solutions obtained after leaching by precipitation. An economic analysis of an REE concentrate extraction facility was also performed. For an operation of 17 years, the calculated NPV was −26,352,644 million EUR. The obtained results indicate that, for the analysed facility, recovering metals and critical raw materials from slag as a waste mass is not economically effective.

Degraded post-mining landscapes require reclamation strategies that ensure soil stability, environmental safety and successful vegetation establishment. This study evaluated two soil cover systems applied between 2020 and 2025 on a mining spoil heap in Libiąż, Poland: a two-layer (TL) cover with a soil substitute layer and a multilayer (ML) cover incorporating additional insulating materials. Both covers were non-saline and mildly alkaline. The applied methods supported favorable soil conditions after five years, with stable organic matter (24.48–28.26%), nitrogen (4.5–4.9 g/kg) and phosphorus (1.5–1.6 g/kg) contents, while potassium decreased markedly (from 17.1 to 6.44–6.83 g/kg), likely due to plant uptake or leaching. Leachate analyses showed low concentrations of toxic metals and salinity-related ions, confirming the environmental safety and inert properties of the soil substitute. Vegetation assessments revealed differences between reclamation systems, with Phragmites australis exhibiting greater stalk length, plant density and biomass in the TL cover. Establishment costs were also substantially lower for TL (EUR 1.65/m²) than for ML (EUR 6.14/m²). These results indicate that soil substitute covers provide a safe, cost-effective and functionally efficient reclamation option that supports circular economy principles by reusing mining waste and coal combustion by-products, while Phragmites australis enhances vegetation development and overall reclamation success.

Raw materials policy plays an increasingly important role in the economies of countries all over the world. The development of new technologies grows the demand for resources. The list of critical resources accepted by the European Committee contains rare earth elements, commonly referred to as REEs. A prospective way of obtaining these elements is recovering them from power industry wastes originating from coal combustion. This publication presents the results of research aimed at evaluating the content as well as illustrating and interpreting the spatial distribution of rare earth elements in power industry wastes deposited in a chosen landfill. It also presents maps of horizontal variability in the content of REEs deposited in certain layers of the ash-slag mix.