As supercapacitor electrode materials, the sustainable biomass-derived activated carbons have attracted a great deal of attentions due to their low-cost, abundant, and unwanted natural wastes. In this work, a facile KOH activation method is adopted to prepare activated carbon tubes from the biomass waste-cotonier strobili fibers for the first time. The resultant PTAC-x materials possess highly accessible surface areas and abundant micro-mesopores, which benefit large ion storage and high-rate ion transfer. The optimized material denoted as PTAC-6 demonstrates a high specific capacity (346.1 F g(-1) at 1 A g(-1)) and a superior rate performance (214.5 F g(-1) at 50 A g(-1)) in the three-electrode supercapacitors. In addition, the symmetric supercapacitor exhibits excellent cycling stability with a capacitance retention of 84.21% and a columbic efficiency of nearly 100% after 10,000 cycles. Furthermore, the PTAC-6-based symmetric supercapacitor gives a remarkable specific energy of 33.04 Wh kg(-1) at 160 W kg(-1). Meanwhile, our proposed porous activated carbon tubes provide a green and low-cost electrode material for high-performance supercapacitors. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.