<p>Powdered silica aerogels are highly porous materials with exceptionally high specific surface area and low density, making them attractive for applications in adsorption, catalysis, or thermal insulation. In this study, sustainable silica aerogels were successfully synthesized from two abundant waste resources, including rice husk ash (RHA) and fly ash (FA), via a sol–gel method followed by freeze-drying. The effects of key synthesis parameters, including HCl concentration during acid pretreatment, NaOH concentration during silica extraction, and pH during the sol–gel process, were systematically investigated. The results reveal that these parameters play critical roles in controlling silica dissolution as well as the hydrolysis and polycondensation reactions governing gel formation and pore development. Under the suitable conditions (HCl 2&#xa0;M, NaOH 1&#xa0;M, and pH ≈ 7), the RHA-derived aerogel exhibited a high specific surface area of 493.3&#xa0;m²&#xa0;g⁻¹, porosity of 97.5%, and pore volume of 0.58&#xa0;cm³&#xa0;g⁻¹, while the FA-derived aerogel showed a surface area of 376.0 m²&#xa0;g⁻¹ and porosity of 96.1%. Scanning electron microscopy confirmed the formation of a typical three-dimensional nanoporous silica network composed of interconnected nanoscale clusters. The obtained materials synthesized in this study exhibit textural properties comparable to those obtained from conventional precursors such as TEOS and MTMS. Importantly, the utilization of RHA and FA demonstrates strong potential for large-scale production and environmental applications.</p>