Man-made fibers like glass, nylon, and aramid contribute to environmental issues, prompting studies on sustainable alternatives like HCS fibers. This research used various characterization techniques to analyze the sustainability of HCS fibers treated with alkaline solutions such as 5% NaOH, benzoyl peroxide with acetone, and KMnO4 with acetone, with the most effective treatment involving a 5% NaOH solution for 60 min. The mechanical and chemical properties of optimally alkalized HCS fibers were compared to raw fibers, showing a 9.07% increase in cellulose content and a 3.03% improvement in fiber density. The removal of non-cellulosic substances was confirmed by increased crystallinity index (from 48.78 to 54.43%) and crystal size (from 1.59 nm to 1.84 nm). TGA analysis showed increased carbon residue and higher degradation temperature for alkalized fibers, which also demonstrated improved surface roughness and tensile strength (447 ± 15 Mpa). These enhanced properties suggest that optimally alkalized HCS fibers have potential for use in FRPC.