# Assessing the Techno-Economic Feasibility of Bamboo Residue-Derived Hard Carbon
## 1 Introduction  
Energy storage is one of the critical challenges in achieving a sustainable energy transition. Renewable energy sources such as solar, wind, and tidal power are inherently intermittent and cannot serve as stable primary energy sources without reliable and efficient energy storage solutions [1]. Among various forms of energy carriers, electricity is the most versatile, making electrochemical batteries a leading option for large-scale energy storage. However, existing commercial battery systems--especially lithium-ion batteries--remain costly, and alternatives often suffer from insufficient energy density or limited scalability. Sodium-ion batteries have emerged as a promising substitute due to the earth abundance of sodium and their potential for cost reduction. Notably, one of the most promising anode materials for sodium-ion batteries is hard carbon, which can be derived from lignocellulosic biomass--the most abundant and renewable carbon source on the planet [2]. Hard carbon is a non-graphitizable carbon material formed by thermally converting organic precursors at elevated temperatures. Unlike highly ordered graphite, hard carbon consists of disordered, anisotropic graphite-like microdomains that aggregate into a turbostatic structure [3]. This unique morphology contributes to its favorable electrochemical properties, including low voltage plateaus and good sodium storage capacity. A key advantage of hard carbon lies in its feedstock flexibility--most lignocellulosic biomass, including agricultural and forestry residues, can serve as viable precursors. Despite the growing interest in biomass-derived hard carbon for sodium-ion batteries, the economic feasibility of producing hard carbon from low-cost and regionally abundant feedstocks such as forestry residues remains underexplored [4]. The production of hard carbon from biomass typically involves high-temperature thermal conversion under an inert atmosphere [4]. In the initial pyrolysis stage (usually below 900 \({}^{\circ}\)C), oxygen and other heteroatoms are removed, resulting in a solid carbonaceous intermediate commonly referred to as biochar. This is followed by further carbonization and graphitization at elevated temperatures, where disordered carbon structures reorganize into short-range graphite-like layers with turbostatic morphology [5]. The entire process involves complex physicochemical transformations, along with the generation of by-products such as bio-oil, syngas, and tar [6]. The properties of the final hard carbon product are highly sensitive to thermodynamic conditions, heating rates, precursor type, and temperature profiles. Accordingly, significant research efforts have been dedicated to elucidating the mechanisms of sodium-ion storage in hard carbon, linking structural features--such as pore size distribution, interlayer spacing, and defect density--to specific charge-discharge behavior [7; 8]. Over the past decade, progress in both mechanism understanding and pilot-scale production has enabled early-stage commercialization efforts [9]. However, there remains a lack of systematic evaluation of the economic viability of biomass-derived hard carbon production, which is essential for accelerating its industrial adoption as a competitive alternative to lithium-ion battery materials. Among various lignocellulosic biomass feedstocks, bamboo is particularly attractive for hard carbon production due to its high areal yield, short growth cycle, and minimal input requirements. In bamboo-rich regions such as southern and southwestern China, extensive cultivation and mature downstream industries--ranging from construction materials to paper and textiles--generate substantial quantities of bamboo residues (BRs) as by-products. These residues are typically concentrated near processing hubs, which can significantly reduce feedstock transportation and logistics costs [10].