European Green Deal (EGD) and the Circular Economy Action Plan (CE) promote recycling of materials in line with circular economy principles and enhance the value of material flows. Recently, new technologies have been introduced to produce value-added products from agricultural residues and food processing side streams. However integrated approach is necessary for organic waste utilization as environmentally safe product according to the bio-economy rules. The so-called opoka-rock is characterized as a transitional rock between carbonate (app. 71%) and those of a silica character (app. 26%). This study identifies research gaps on how circular bioeconomy can be achieved through application of opoka for improvement of sustainable nitrogen and phosphorous management of poultry manure as safe fertilizer according to CE. Initially, it was found that opoka was able to effectively absorb the N and P ions from water solution and then gradual release to environment. Thermal treatment (900 °C) increased rapidly sorption capacity of opoka to 100% in the case of phosphorous, value of pH and content of Ca2+ions in eluates. Moreover, the volume ratio of opoka to poultry manure in experimental mixtures was optimized to determine of nitrogen and phosphorus release into the solution. The substrate was characterized by good desorption properties - the tests confirmed gradually release of N and P ions to solution with the maximum concentration obtained after 32 h equal almost 71% of initial value in mixtures in the case of phosphorous and almost 40% in the case of nitrogen. The novelty of such approach gives opportunity use opoka-rock not only as a single sorbent but also for improvement of poultry manure as mineral-organic fertilizers in the context of CE. This also allow to control for ions N, P release and maintain suitable pH value of soil environment.
Keywords: Adsorption; Circular economy; Desorption; Mineral-organic fertilization; Nitrogen; Opoka-rock; Phosphorous; Poultry.
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