## 1 Introduction  
Market and research are in the constant pursuit of new technologies and treatments to improve the properties of mechanical components. Human society has been increasing the magnitude of global production constantly for several decades. Environmental problems such as waste management, and the need to reduce CO\({}_{2}\) and other pollutants and to produce energy in a sustainable way, are creating pressures on the research to find new sustainable materials and technologies. Biochar could play a major role in this process. The biochar consists in the carbonized biological material obtained through thermochemical conversion processes such as pyrolysis and gasification [1]. Nowadays, biochar has well-documented applications, such as geopolymers addition [2], insulation materials production [3], water remediation [4, 5], and soil amendment [6, 7]. Biomass-derived char is also gaining interest in high-tech carbon-based materials, i.e., using biochar as a graphene precursor [8, 9] or blending graphene and biochar to produce new materials [10]. Within this literature framework, the presented work aims to investigate the possibility of including biochar as a carbon source in electrospun PolyAcryloNitrile (PAN)-based carbon nanofibers. The literature review shows a few attempts to use carbon sources derived from biomass thermochemical conversion in electrospun fiber production: [PERSON] et al. [11], in their literature review, investigated the preparation of carbon nanofibers from biomass and biopolymers as precursors using electrospinning as the manufacturing method; [PERSON] et al. in 2018 used additivated and non-additivated pyrolysis bio-oil in a melt-spinning process [12]; [PERSON] et al. in 2017 and [PERSON] et al. in 2021 both included char from hydrothermal liquefaction in PAN-spun fibers [13; 14]. Gasification-derived biochar has still not been investigated in the literature, opening the question of the feasibility of the proposed aim. Pyrolysis and hydrothermal gasification are widely used for char production due to the large biochar yield values (up to 30%wt) that can be obtained from these processes [1]. On the other hand, pyrolysis and hydrothermal carbonization are endothermic processes that require an external source of heat to operate [1]. Gasification systems produce less char compared to pyrolysis (about 2-10%wt. ), but they have the major advantage that biochar is the byproduct of a renewable bioenergy (thermal and/or electric) production process [1]. A second advantage relies on the specific biochar production conditions in gasification reactors: gasifiers are characterized by higher temperatures (600-1100 \({}^{\circ}\)C) compared to pyrolysis reactors (300-600 \({}^{\circ}\)C). These conditions create a more regular physical structure of the gasification biochar that moves toward the graphene one, as it is described in [15]. Therefore, this study aims to investigate whether gasification-derived char can be included as a carbon source in carbon fiber production. Carbon NanoFibers (CNFs) are fibers less than 1 \(\upmu\)m in thickness. These fibers are a new class of superior engineered materials due to their excellent mechanical and electrical properties. CNFs reach 600 GPa in Young's modulus [16; 17]. CNFs and carbon fibers are usually fabricated through various spinning methods. After spinning, the fibers undergo the heat treatment, which allows the carbonization of the material. This thermal process is divided into two: stabilization and carbonization [18; 19]. The spinning system uses a solution composed of a polymer and a solvent. The concentration ratio of the solution is usually in the range of 10-30% of polymer/70-90% solvent, depending on the applications [18; 20]. Further to the mechanical properties, CNFs are particularly interesting due to the range of possible applications, among which filtration plays a major role. The process takes advantage of the small diameters and a high surface area/volume ratio.