Valorization of Biomass Gasification Char as Filler in Polymers and Comparison with Carbon Black

Char, the solid residue produced during biomass gasification, is usually treated as a waste with high environmental and economic costs associated to its disposal. However, char shows remarkable properties that make it suitable for a plethora of different applications. In particular, this study aims at investigating the feasibility of using char as filler in polymers for boosting polymer thermal stability and electrical conductivity, and comparing its performances with carbon black (CB), a more traditional carbonaceous filler. Char residues were collected from a commercial biomass gasifier, thoroughly characterized, and compared with CB. Both materials were used in combination with a styrene–ethylene–butylene–styrene (SEBS) matrix for the production of two different compounds, deeply characterized as well. An addition of 44 wt% of char increases the thermal stability of the compound and its electrical conductivity up to 2× 10−3 S cm−1, without interfering with its structure and mechanical properties. Less CB (20 wt%) was needed for obtaining composites with the same electrical conductivity. The findings of this study pave the way for new valorization routes for large amounts of char in cutting-edge applications and present the opportunity to the polymer manufacturing to use a high-available and low-cost substitute for carbon-based fillers.