Conversion of Biomass into porous carbon with high yield is a huge challenge due to the consumption of plentiful carbon during pore-forming. Here, we employ the biomass materials as the activation agent to circumvent the excessive etching effect of the conventional chemical reagent. Both green activation agent and raw material are converted into porous carbon, which results in ultrahigh yield (even more than 100%). Furthermore, the biomass activation agent with abundant metal elements not only contributes to pore-forming but also achieves heteroatom doping. The obtained N-doped hierarchical porous carbon presented good capacitive capability (150.1 F g(-1) at 0.2 A g(-1)) and high rate performance (similar to 61% of capacitance retention from 0.2 to 50 A g(-1)). The green activation process achieves both the increase of yield and excellent capacitive properties for the first time. The green strategy proposed in this work for producing porous carbon with high yield provides a new consideration on comprehensive utilization of biomass resources. (C) 2020 Elsevier Ltd. All rights reserved.