Processing and characterization of biogenic SiO₂ and CaO from rice husks and eggshell waste materials

Agro-poultry wastes, which are generated by the combined activities of agricultural and poultry operations, are a valuable but underutilized resource with significant environmental and economic implications. By converting these waste materials into valuable resources, we can promote a circular economy approach that reduces environmental impact, fosters sustainable practices, and contributes to resource conservation. In this regard, this study investigated the feasibility of rice husks (RH) and chicken eggshells (CES) as sustainable sources of biogenic silica (SiO₂) and calcium oxide (CaO), as alternatives to commercially sourced materials. Both thermal treatment and chemical extraction methods were employed to extract these biogenic compound. Characterization studies revealed that EGSA has a CaO content of 95.3%, which is comparable to that of commercially pure CaO (C_CaO) at 90.4%. Both EGSA and C_CaO had fine-grained morphologies with even distribution. The SiO₂ content of RHA and RH_SS was 87.6% and 94.59%, respectively, approaching that of commercially pure SiO₂ (CSi) at 95.9%. RHA and CSi shared a predominantly crystalline silica phase, while RH_SS exhibited an amorphous silica phase. These findings demonstrate the promising potential of biogenic SiO₂ and CaO derived from agro-poultry wastes as sustainable alternatives to their commercially available counterparts.