The first family of threshold (ppm level) cellulose-based scale inhibitors and crystal modifiers has been developed through the chemical nanoengineering of cellulose fibrils, the building blocks of plant cell walls, overcoming the structural and chemical limitations of conventional nanocelluloses. Dicarboxylated hairy cellulose nanocrystals and biopolymers address one of the most tenacious challenges of water-based industries, i.e., the scaling of inorganic salts, providing a green, environmentally-friendly alternative to the current phosphonated macromolecules. This research may shape the future of biomass-based antiscalants and advance the field of organic–inorganic biomimetic nanocomposites based on the most abundant biopolymers in the world.