Development of circular bioeconomy strategies for the integrated management of tequila vinasses

Abstract

The agro-food industry is one of the largest productive sectors globally, by volume and economic relevance. Food demand is expected to keep increasing with the global population, increasing environmental strains by raw resource consumption and intensive waste generation. The circular bioeconomy model aims to reduce resource depletion and waste generation from bio-based production systems, such as the agro-food industry, by the circularization of material and energy flows into productive processes. The aim of the present thesis is to evaluate the implementation of novel circular bioeconomy approaches for the tequila industry, focusing on the integral management of tequila vinasses (TV). The first part of the present thesis presents an integrated approach for the assessment of environmental sustainability in agro-industrial waste management practices. This encompasses an extensive physicochemical characterization of spatially distributed vinasses samples within the state of Jalisco, the implementation of a geographic information system to characterize the spatial distribution of the waste production and the implementation of mathematical models to evaluate management scenarios in terms of their environmental impacts and their potential for low-value material recovery. The second part of the thesis presents a circular bioeconomy alternative for the simultaneous treatment and revalorization of TV into animal feed supplements by the culture of fodder yeast species (Candida utilis, Kluyveromyces marxianus y Rhodotorula mucilaginosa). Culture treatments (monocultures and mixed cultures were evaluated for the removal of pollutants (Chemical oxygen demand (COD), total nitrogen (TN) , and total phosphorus(TP))as well as protein production. Additionally, TV concentration was evaluated as an additional factor of the experimental design. A weighted response index was used to evaluate the treatments and the culture treatments that displayed the best performance were selected for benchtop-scale escalation. Benchtop-scale cultures were monitored every 8 hours for a 48-hour period, during which 6 parameters were determined (COD, TN, TP, viable biomass, protein, reducing sugar concentrations). For the benchtop-scale, the kinetic parameters in a mass balance model based on the Monod equation were determined for a mass balance model using a differential neural network and an optimization algorithm. The biomass obtained from the benchtop-scale cultures was spray dried and analyzed to determine its amino acid composition and evaluate its applicability as an animal feed supplement. Further research is required to allow the escalation of the proposed biorefinery process from lab-scale to pilot-scale to guarantee its economic and technical feasibility. The results obtained in the present work have shown that the implementation of circular bioeconomy models has the potential to significatively reduce environmental strains caused by linear agro-food industrial systems and can help achieve local and international commitments toward sustainability. The integration of both low-value and high-value biological recovery strategies on the local and regional context could significatively reduce organic and nutrient pollution by its recovery either as low-value components (biogas, fertilizers, and sludge) or as high-value products (protein and biomass for animal feed supplementation) while increasing the economic viability of waste management through the commercialization of recovered byproducts. The reduction of treatment costs and the new economic incentives offered by the revalorization of agro-food waste can be beneficial for small and micro producers, who lack the capital required for higher infrastructure investments. This study lays the foundation for policy makers to establish guidelines, programs, incentives, and regulations to guide the tequila production sector towards the development of circular economic models based on scientifically sound methodologies