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**100**

Chapter 6

Abstract

biofuels

103

and tequila vinasse

A Comprehensive Overview of

the Potential of Tequila Industry

By-Products for Biohydrogen and

Biomethane Production: Current

Status and Future Perspectives

Octavio García-Depraect, Daryl Rafael Osuna-Laveaga

Nowadays, the use of agro-industrial by-products as alternative sustainable resources to generate bioenergy and high-value bioproducts is one of the most important research topics to tackle environmental concerns related to the excessive consumption of fossil-based fuels and rapid urbanization and industrialization. This chapter provides a broad overview of the potential of the main tequila industry by-products, agave bagasse and tequila vinasse, for biohydrogen (bioH2) and biomethane (bioCH4) production via dark fermentation and anaerobic digestion, respectively. First, pretreatment or conditioning steps commonly applied to tequila by-product streams before downstream biological processes are highlighted. The operational performance of bioH2- and bioCH4-producing reactors is subsequently reviewed, with a focus on reactor configuration and performance, microbial metabolic pathways, and the characterization of microbial communities. Additionally, the development of multi-stage anaerobic digestion processes is comprehensively discussed from a practical point of view. Finally, limitations and potential improve-

Keywords: agave bagasse, tequila vinasse, dark fermentation, anaerobic digestion,

1. Tequila production process and its main by-products: agave bagasse

Tequila is a Mexican alcoholic beverage obtained from the distillation of fermented juice of the mature stems of Agave tequilana Weber var. azul. It possesses appellation of origin since 1974 and has received international recognition in the market. As an example, tequila-processing plants produced around 309 million liters of tequila in 2018, of which 72% were exported, highlighting its international demand [1]. Thus, tequila production represents one of the most important activities for Mexico. In general, there are three major stages in the tequila production

ments in the field of bioH2 and bioCH4 production are presented.

and Elizabeth León-Becerril
