Technosol Development Based on Residual Fraction of Coal Tailings Processing, Agro-Industrial Waste, and Paper Industry Waste

In order to obtain solutions to the coal mining region demand in southern Brazil for high-performance and low-cost technosols within a concept of mineral circularity and sustainable development of the coal sector, this study aims to evaluate the functional feasibility of the combined use of a residual fraction of coal tailing, waste from the rice and poultry agro-industry, as well as the cellulose industry, as raw materials for technosol development. Characterizations (XRF, LOI, ICP-OES, pH, XRD, and sulfur forms) were performed to adjust the waste proportions used in the constructed soil, as defined based on the clay content of the coal tailing, the organic carbon content of the poultry litter, and technical recommendations for the use of synthetic gypsum in agricultural soils. Based on the characterizations of the residues, a greenhouse experiment was designed, consisting of four technosol formulations (T1-T4). Initially, an ecotoxicity test was conducted with the treatments in contact with Allium cepa L. (onion) to determine the degree of technosol toxicity. Field tests were then carried out, which were replicated three times in a completely randomized block design, with the germination and growth of Lactuca sativa L. (crisp lettuce) as a bioindicator. The fertility of the treatments was analyzed eight weeks after the establishment of the experiment and compared to standard values for agricultural soils. The characterization performed with the individual wastes demonstrated the potential for application in technosols according to current regulations. The ecotoxicity tests showed that the soil was not toxic to the plant in any of the treatments studied. The field experiment demonstrated no difference in germination between the treatments. However, the development of lettuce seedlings occurred only in technosol formulations T2 and T3, highlighting the potential of the studied residues for the construction of technosols.