A green, cost-effective and sustainable route was proposed for the production of nitrogen-doped porous biochar with a sheet-shaped structure. Gelatin (G) served as carbon and nitrogen sources, and sodium chloride (SC) functioned as not only a porogen but also a two-dimensional structure-directing template. In particular, the used SC salt can be easily recovered for reutilization, which eventually leads to a closed-loop process. Furthermore, a G/SC mass ratio of 1/30 and a carbonization temperature of 750 °C were demonstrated to be the optimal conditions for producing biochar which integrates advantages including the abundant pore structure, the high graphitization degree and the optimized doping of nitrogen species and thus affords an enhanced charge storage capacity. This work takes a step towards green chemistry for the large-scale production of functional biochar, and the correlation of the microstructure and surface chemistry with electrochemical performance provides valuable guidance for the design and configuration of functional carbon nanomaterials.