Circular economy: Tequila vinasse treatment for upcycling and downcycling

Abstract

Tequila is one of Mexico's most iconic distilled beverages, with a steadily growing industry that also embodies a significant cultural legacy. However, most tequila producers in the country face challenges in managing the waste generated during production due to the high costs of treatment and the low economic returns from by-products. This thesis begins by exploring the intricate relationships between tequila production and various industrial, environmental, and governmental sectors through a comprehensive mapping process. The second section examines the production of distillates, including bioethanol, tequila, and other alcoholic beverages, focusing on the treatment of substantial liquid waste known as vinasse, which is produced at a rate of 10-15 liters per liter of distilled product. This waste presents critical environmental challenges, such as eutrophication, soil pollution, and toxicity. A systematic review conducted in this thesis evaluates various pathways for valorizing distillery vinasse. The review includes 72 treatments involving ethanol industry vinasse, tequila vinasse, and their combinations with agro-industrial residues, categorized into three main valorization strategies: waste-to-energy, waste-to-food, and waste-to-product. Biotechnological treatments, such as two-stage anaerobic digestion and fungal anaerobic fermentation, achieved the highest yields and product diversity. Moreover, bacterial processes demonstrated significant potential for producing high-value products like polymers, enzymes, and proteins. The third part of this thesis is about an aerobic treatment in co-cultures and monocultures using strains like C. utilis, R. mucilaginosa, K. marxianus, A. niger, A. oryzae, and R. oligosporus were explored for contaminant removal and high-protein biomass production. The C. utilis and A. oryzae co-culture generated the best results at the tube scale, showing remotion up to 63.52% TN removal, 86.87% P removal, and 46.21% COD removal over 72 hours in the benchtop scale. A kinetic study modeled biomass growth using a biphasic Zwietering-modified Gompertz model, achieving a maximum protein of 47.27 g kg⁻¹. The thesis also explores other high-value products using this substrate, such as phenols, and the importance of these remotions.