<p>Aerogels, recognized for their 3D porous structure and high porosity, hold significant potential for oil–water separation. So many preparations of aerogels have been widely reported. It is still challenging to prepare high porosity efficiently and cost-effectively. This study presents a green, simple, and efficient approach to aerogel production, using cellulose and cellulose nanofibers from sorghum bagasse waste as the framework, with polyvinyl alcohol as the crosslinking agent, lead formation of hydrogen bonds to form a stable three-dimensional network structure. Ultrasonic treatment significantly enhanced their aspect ratio. The resulting aerogel features a low density (&lt; 6.3&#xa0;kg/m³) and high porosity (&gt; 99.4%). After hydrophobic modification with methyltrimethoxysilane through chemical vapor deposition, the aerogel achieves excellent hydrophobic properties, with a water contact angle of 146°. It demonstrates strong absorption capabilities for oil and organic solvents, with an oil absorption capacity of 89&#xa0;g/g. Importantly, the aerogel retains its high absorption capacity after ten cycles, highlighting its excellent reusability. In conclusion, this aerogel represents a promising solution for valorizing Sorghum bagasse (BG) waste and shows significant potential in oil–water separation applications.</p> Graphical abstract <p></p>