Sintesis Nano-Biochar Dari Lignin Tandan Kosong Kelapa Sawit (TKKS) Sebagai Komplemen Karbon Pada Vulkanisasi Styrene Butadiene Rubber (SBR) Dengan Carbon Black N-550 = Synthesis of Nano-Biochar from Oil Palme Empty Fruit Bunches (OPEFB) Lignin as Carbon Complement in Vulcanization of Styrene Butadiene Rubber (SBR) with Carbon Black N-550