Production and Evaluation of Lime Fertilizers with the Addition of Biomass Combustion Waste

The study identified the optimal material, e.g., raw composition and moisture content, and process parameters for the non-pressure agglomeration of carbonate lime combined with biomass waste, e.g., calcium sulfate (ECO-ZEC), post-production residue (PPR), and fly ash using a molasses-based binder. The chemical analysis revealed that the CaO content in the granules ranged from 34% to 52%, with the highest calcium concentration observed in formulations containing carbonate limestone. Among the waste-based additives, PPR exhibited a calcium content only 7% lower than that of pure carbonate lime, whereas ECO-ZEC and fly ash contained 20% and 30% less calcium, respectively. Due to the low MgO levels in the tested granules, they cannot be classified as calcium-magnesium fertilizers. Regarding heavy metal content, concentrations of cadmium and lead remained below the permissible regulatory limits. The highest levels of these elements were detected in the fly ash-enriched granules, consistent with the known chemical composition of this waste type. The tested waste materials ECO-ZEC, PPR, and fly ash demonstrated alkaline pH values ranging from 12.37 for fly ash and 12.28 for PPR to 8.84 for ECO-ZEC. The reference carbonate lime showed a slightly lower pH of 8.82. Mechanical strength testing indicated that the addition of PPR improved the mechanical resistance of the granules compared to the reference sample. Conversely, the inclusion of ECO-ZEC and fly ash reduced this parameter. Notably, granules containing fly ash and PPR exhibited prolonged disintegration times in water, suggesting their potential application as slow-release fertilizers. The findings of this study demonstrate that industrial waste materials generated from biomass combustion can serve as effective components in the production of innovative lime-based fertilizers. This innovative approach not only promotes the recycling of by-products but also supports the development of sustainable agriculture by reducing the environmental burdens associated with waste disposal and encouraging resource efficiency.