<p>This research demonstrates a sustainable and low-cost method for producing hydrophobic coatings using silica derived from sugarcane bagasse ash, an abundant agricultural by-product containing 60–80 wt% silica. The silica was extracted through alkaline treatment with sodium hydroxide followed by acid precipitation, yielding a stable silica solution. Although other biomass residues such as rice husk ash and wheat straw ash are also potential silica sources, the present study emphasizes sugarcane bagasse ash for its wider availability and higher silica content. The coatings were fabricated on three different substrates: glass plates, ceramic tiles, and cotton cloth to evaluate performance across both smooth and porous surfaces. Structural and chemical features of the silica were confirmed using powder X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. Hydrophobic properties were investigated through water contact angle measurements at different pH levels (3, 5, and 7). The results show that ceramic tiles achieved the highest water contact angles of 131.2 ± 1.7^o, 130.1 ± 2.7^o, and 137.9 ± 2.4^o, indicating strong and stable water repellency. Glass plates exhibited moderate hydrophobicity with values of 94.5 ± 8.0^o, 102.7 ± 2.1^o, and 101.0 ± 1.8^o, whereas cotton cloth showed pH-sensitive behavior with contact angles of 99.8 ± 13.0^o, 125.1 ± 4.2^o, and 119.5 ± 11.8^o and corresponding water retention volumes of 329.7%, 25.0%, and 183.2%. These findings highlight that silica from sugarcane bagasse ash can be effectively applied to multiple substrates, offering a scalable and eco-friendly alternative to synthetic hydrophobic materials while supporting circular economy practices.</p>