An efficient, environmentally friendly flame-retardant process for lignocellulosic material was developed based on a renewable phosphorus flame retardant. The whole process which is easy to implement and to scale up is patented. The effectiveness of the treatment was proved by the analyses of pyrolysis-combustion flow calorimetry (PCFC), a flame test, X-ray fluorescence, 31P and 13C NMR and optical microscopy. Grafting of ≈ 0.5%P and ≈ 0.7% N was sufficient to produce a non-flammable material by a synergistic P/N effect. This process was successfully applied to cellulosic fibers and wood particles for the production of fire-resistant wood panels. The analysis of these panels showed not only an efficiency in fire behavior but also an improvement in mechanical and hygroscopic properties. The implementation of the process in different industrial production lines will be exposed.