There is an ever-growing demand for biochar production and its chemical transformation into specialty materials. Herein, we suggest a versatile method to elaborate Ag/Cu nanoparticles, by phytochemical process, on aryl-sulfonated sugarcane bagasse pulp-derived biochar. A binary nanocomposite has been fabricated through a four-step strategy. The raw substrate biochar was first prepared by a slow pyrolysis of the biomass at 500 degrees C under N-2:H-2 95\%:5\% inert atmosphere. Thereafter, in situ arylation of the biochar surface has been performed to obtain SO3H-Biochar. The loading of silver and copper ions on SO3H-Biochar has been achieved via a wet impregnation using a hydroalcoholic medium. Finally, the natural extract obtained from sugarcane bagasse has been employed to ensure the reduction of the adsorbed metal ions and obtain SO3H-Biochar@Ag/Cu. Interestingly, the structural analysis of SO3H-Biochar@Ag/Cu and the study of the evolution of D to G band intensity and area ratios have revealed that the metal phase deposition has altered the SO3H-Biochar surface properties. It finally provided a more graphitized nanocomposite compared with the bare biochar and the intermediate substrate (SO3H-Biochar). Such a result suggests that the phytochemical reduction has catalyzed the substrate graphitization. The catalytic performance of SO3H-Biochar@Ag/Cu has been investigated in the oxidative degradation of malachite green oxalate. A total mineralization of the dye has been registered, and the experimental data were found to give a best fitting to the pseudo-first-order model. The fitting was relatively good with a mineralization apparent constant rate equals to 65 10(-3) min(-1). It is worth mentioning that all experiments used a relatively low amount of the composite catalyst (2.5 mg). So to recap, this route takes advantage of the two phases of sugarcane bagasse to generate a robust biochar-based catalyst, its solid phase to derive biochar substrate with particular properties, and its liquid extract to be used as natural reducing preparation.