GREEN cellulose aerogels from paper waste were successfully synthesized cost-effectively by using alkaline/urea and freeze drying/supercritical drying processes. The cellulose aerogel structures could be optimized by various recipes for high absorbance applications of polar liquids (water) and non-polar liquids (spilled oil), and excellent eco-friendly heat insulators (very low thermal conductivity and water repellent for tropical climate usage). The hydrophobic property of the cellulose aerogels were significantly improved by coating the whole porous structure with a few nanometers of MTMS through chemical vapor deposition. The developed recipes and methods can be scaled for the mass production with various sizes and shapes.