Sustainable Conversion of Brewery Waste into Biochar via Pyrolysis: Influence of Operational Parameters

Brewers’ spent grain (BSG), the major by-product of the beer industry, represents a widely available and underutilized lignocellulosic residue with strong potential for sustainable valorization. This study investigates the pyrolysis of BSG under controlled conditions to produce carbon-rich biochar and evaluates how particle size (300 and 600mm), temperature (500 and 700°C), and residence time (1h and 2h) influence product yields and structural development. The feedstock exhibited an exceptionally high moisture content (75 ± 2.34%), emphasizing the importance of pre-drying to improve thermal conversion efficiency. Biochar yields ranged from 22.51% to 41.32%, strongly dependent on the operational parameters, with higher temperatures and smaller particles promoting enhanced devolatilization and gas formation. Comprehensive characterization through FTIR, XRD, Raman spectroscopy, and TGA revealed predominantly amorphous carbon structures, extensive loss of oxygenated functionalities, and the presence of mineral phases typical of mid- to high-temperature pyrolysis. These results confirm that BSG is a promising renewable precursor for engineered biochars and demonstrate how fine control of pyrolysis conditions enables tailored physicochemical properties. Importantly, the structural and chemical features identified in this study establish a solid foundation for future activation processes aimed at converting BSG-derived biochar into high-performance activated carbons, opening pathways for advanced adsorption and environmental remediation applications. This research is funded by São Paulo Research Foundation (FAPESP) with grants 2024/01112-1 and 2025/17942-6.