317 Silicate Agromineral, Remineralizer, Fertilizer, Coproduct, Mining, Waste Rock 1. INTRODUCTION Brazil is one of the world’s largest agricultural producers, but much of its cropland is developed on highly weathered tropical soils with low base saturation and pervasive acidity, making soil amendments and nutrient replenishment essential for sustaining yields. At the same time, the country remains strongly dependent on imported fertilizers; the National Fertilizer Plan (PNF) highlights that Brazil accounts for ~8% of global fertilizer consumption and historically imports around 85% of the fertilizers it uses, motivating policies to expand domestic alternatives and circular-economy solutions (MAPA, 2025). In this context, mining companies such as Vale have an opportunity to align mineral production with decarbonization targets by transforming suitable waste rocks into agricultural inputs. Rock powders produced by crushing and milling silicate rocks can act as multi-nutrient amendments, soil remineralizers and conditioners, supplying K, Ca, Mg and trace elements while improving soil chemical conditions, especially in acidic systems where base cation inputs alleviate Al toxicity and increase base saturation (van Straaten, 2006). Recent studies with basaltic rock powders report increases in soil pH and exchangeable bases and, in some cases, improved crop performance, reinforcing the potential of mafic quarry by-products as low-cost, regional nutrient sources (Luchese et al., 2023; Richardson et al., 2024; Theodoro et al., 2021; Zuffo et al., 2022). In Brazil, Law 12,890/2013 established the legal framework for the producing and commercializing these materials as soil remineralizers, defining them as mineral inputs obtained by mechanical size reduction and classification that improve soil fertility by supplying macro- and micronutrients and by enhancing physical, physicochemical, or biological properties. Under this legislation, soil remineralizers are defined as “mineral materials processed by mechanical size reduction and classification that improve soil fertility by supplying macro and micronutrients and enhancing physical, physicochemical, or biological properties.” To ensure the quality and safe application of these materials, Normative Instruction No. 5 (MAPA, March 10, 2016) specifies the required standards for chemical composition (CaO + MgO + K2O > 9%; K2O > 1% and maximum thresholds for potentially toxic elements (As <15 ppm, Cd < 10 ppm, Hg < 0.1 ppm, Pb < 200 ppm), mineralogy (quartz < 25 vol%) and grain size distribution (powder 100% < 2 mm, 80% < 0.84 mm, 50% < 0,3 mm; filler 100% < 0,3 mm). These criteria provide a regulatory foundation that guides the evaluation and certification of soil remineralizers for agricultural use. Beyond agronomic benefits, finely ground mafic rocks have gained prominence in climate-mitigation strategies via Enhanced Rock Weathering (ERW). ERW accelerates the natural weathering of Ca- and Mg-bearing minerals, increasing alkalinity (bicarbonate formation) and enabling durable CO₂ removal while potentially delivering co-benefits for soil fertility (Hartmann et al., 2013; Beerling et al., 2020). This dual function strengthens the rationale for converting suitable mining waste rock into certified remineralizers.
RkJQdWJsaXNoZXIy MTM0Mzk2