Towards Circularity: Integrating biochar production from maize stover into the tequila industry

Abstract

Maize stover and tequila vinasses require sustainable management. This study aims to assess the feasibility of maize stover biochar (MS-BC) as a low-cost alternative for treating vinasse contaminated water. A comprehensive approach encompassing experimental and simulation methodologies was employed to assess the economic, technological and environmental viability of MS-BC. Commercially available granular activated carbon from coconut shell (CN-GAC) was used for filtration comparison by evaluating reduction capacities for chemical oxygen demand (COD), phosphate (TP), and nitrogen (TN). Afterwards, a comprehensive process simulation was performed in SuperPro Designer to analyze production of MS-BC, energy, and bio-oil. The analysis was further enhanced with a cradle-to-grave life cycle assessment (LCA). Filtration media characterization revealed distinct physicochemical properties. In filtration experiments, CN-GAC and MS-BC slightly reduced COD (4.53 % vs. 3.34 %, respectively), but considerably reduced TN (48 %, 40 %). CN-GAC outperformed MS-BC in all cases; notably, MS-BC leached TP. The economic evaluation indicates MS-BC is profitable, suggesting enough cost margin for biochar pretreatment. Achieving technical parity with CN-GAC requires further research on pretreatments, lifetime, maintenance, and operational conditions in the context of tequila vinasse filtration. Sensitivity analyses of financial indicators for feedstock cost, carbon credits, biochar and energy price were performed. Profitability displayed high sensitivity to all four factors. The LCA revealed environmental advantages of MS-BC over CN-GAC on 12 of the 18 ReCiPe methodology indicators despite TP leaching. The GWP was −0.409 and −0.273 kgCO₂eq/L of treated influent for MS-BC and CN-GAC, respectively. Activation of MS-BC did not improve most of the environmental performance indicators.