The synthesis of nano silica from agricultural waste is a sustainable and environmentally friendly alternative to traditional methods that address both waste management and material production issues. Abundant agricultural waste, such as sugarcane bagasse ash (SCBA) and rice husk (RH) as shown in Fig. 1, is frequently mismanaged, resulting in substantial environmental burden. Repurposing this waste for nano silica synthesis prevents this by reducing environmental waste and lowering dependency on energy-intensive commercial silica production. Green synthesis of nano silica has been largely explored by focusing on their applications in in nanotechnology, biomedicine, and construction over the years. This review paper, in contrast, discusses the synthesis of nano silica from agricultural waste using a variety of procedures, including sol-gel processes, precipitation methods, acid and alkali treatments, hydrothermal reactions, and other novel approaches as well as their application in pavement engineering. This review compiles the various methodology reported for synthesis of nano silica from agricultural waste in the past two decades (2004 to 2024) and highlights the limited research on its use in asphalt, helping to identify gaps and guide future studies in sustainable infrastructure (Refer Fig. 1 for Graphical Abstract).
