This article presents a method to precipitate zinc (lignin/silica/fatty acids) complex (Zn LSF complex) from the black liquor of pulped rice straw and studying the efficiency of it as green activator and antioxidant in natural rubber composites. The results obtained revealed that the investigated zinc complex has dual function as activator and antioxidant in natural rubber composites. This evaluation was supported by physico-mechanical properties of the vulcanizates which showed a considerable improvement of rheometric characteristics, tensile strength, strain at break, hardness, Young's modulus, thermal oxidative aging, and thermal stability of NR composites. The composite loaded with 7 phr of Zn LSF complex as activator exhibited the best mechanical properties in comparison with the same concentrations of control activator zinc stearate. Also, results revealed that Zn LSF complex is efficient as antioxidant in NR vulcanizates compared conventional antioxidants, namely polymerized 2,2,4-trimethyl-1,2-dihydroquinoline. POLYM. ENG. SCI., 59:E196-E205, 2019. (c) 2018 Society of Plastics Engineers