Principles of inexpensive biotechnology are being increasingly used to address the problems posed by the use of lithium-sulfur batteries. We used chitin, a low-cost marine biowaste product, as a precursor for the in-situ preparation of chitin-derived nitrogen-doped hierarchical porous carbon fibers (CNHPCFs) containing abundant pores. These materials are characterized by varying morphologies and high specific surface areas and present a hierarchical porous structure. CNHPCFs adsorb polysulfides, exhibit good ionic conductivity, and can be potentially used to generate green energy. These properties help address the problems of volume expansion and slow transport. The CNHPCF-1@S cathode exhibits excellent cycling performance and high capacity (1368.80 mAh·g⁻¹ at 0.2 C; decay rate: 0.011% per turn at 5 C). The high electrochemical reversibility recorded for CNHPCF-1@S and the stepwise reaction mechanism followed were studied using the in-situ X-ray diffraction and in-situ Raman spectroscopy techniques. The results reported herein can potentially help develop new ideas for the recycling and treatment of marine biofertilizers. The results can also provide a platform to improve the application prospects of lithium-sulfur batteries.