The management and final disposal of agro-industrial wastes are one of the main environmental problems. Due to the presence of silica in some agricultural by-products, it is possible to convert waste into materials with advanced properties. This contribution was aimed to extract and characterize silica materials from various feedstocks including sugarcane bagasse (SCB), corn stalk (CS), and rice husk (RH). Silica yields of 17.91%, 9.39%, and 3.25% were obtained for RH, CS, and SCB. On the other hand, the textural properties show that the siliceous materials exhibited mesoporous structures, with high silica composition in the materials due to the formation of crystalline SiO2 for SCB and CS and amorphous for RH. XPS spectra demonstrate the presence of Si4+ species in RH, and Si3+/Si4+ tetrahedra in SCB and CS.