The present disclosure provides capacitors for storing electrical energy. The capacitors can comprise, at least in part, bast fiber, bast powder, hurd fiber, hurd powder, or a derivative thereof. In some instances, a dielectric of a capacitor can be formed of bast fiber, bast powder, hurd fiber, hurd powder, or a derivative thereof. In other instances, one or both electrodes of the capacitor can be formed of bast fiber, bast powder, hurd fiber, hurd powder, or a derivative thereof. The resulting capacitors can be configured to have various power densities and various energy densities over various minimum numbers of charge/discharge cycles at a certain specified range of operating temperatures.