Thermochemical conversion of biomass produces tar, as an inevitable byproduct, which was a potentially precursor for carbon material preparation. This study provided an approach of preparation of tar-based Fenton-like catalytic nanoparticles from waste biomass tar via green solvent-free approach. The monoand bimetallic nanocatalysts were synthesized from biomass tar and metal salts by ball milling combined with calcination. The synthesized catalysts were utilized for H2O2 decomposition and subsequent methylene blue (MB) degradation in aqueous solution. The results showed that the presence of tar resulted in the porous structure and defective graphite layers on the surface of resultant catalysts. The bimetallic nanocatalysts had higher H2O2 decomposition rate than monometallic nanocatalysts and among all the catalysts, the bimetal catalyst prepared at 300 degrees C (FeNi/C-300) showed the highest rate constant (10.55 x 10(-3) min(-1)) for the decomposition of H2O2. This high catalytic activity of FeNi/C-300 was attributed to the promotion of Fe3+ reducing to Fe2+ due to accelerated electron exchange by the introduction of nickel and the formation of defective graphite layers. For MB degradation, the monometal nanocatalyst prepared at 300 degrees C (Fe/C-300) and FeNi/C-300 showed high removal efficient in the degradation of methylene blue, and the highest removal efficiency reached 100% and 98%, respectively. This study offered a promising approach for the preparation of heterogeneous Fenton catalytic nanoparticles for organic pollutant removal using waste biomass tar and by green synthesis method. Most importantly, this approach has the potential to be extended for other metal based Fenton catalytic nanoparticles synthesis. (C) 2019 Elsevier Ltd. All rights reserved.