Three-stage process for tequila vinasse valorization through sequential lactate, biohydrogen and methane production

Area of Science:

• Biotechnology
• Environmental Science
• Renewable Energy

Background:

• Tequila vinasse (TV) is a challenging agro-industrial waste.
• Valorization of TV into valuable products like biohydrogen and methane is crucial.

Purpose of the Study:

• To develop and evaluate a novel three-stage cascade process for simultaneous lactate, biohydrogen, and methane production from TV.
• To optimize biohydrogen production rate (HPR) using lactate as a precursor.

Main Methods:

• A sequencing batch reactor was used for the first stage to maximize lactate production.
• Lactate-centered dark fermentation was employed in the second stage to decouple biohydrogen production.
• A methanogenic stage processed the effluent from the second stage.

Main Results:

• Sustained lactate concentration of 12.4 g/L (89% of total organic acids) in the first stage.
• Stable biohydrogen production with HPR fluctuations <10%, a maximum HPR of 12.3 L/L-d, and a yield of 3.1 L/L_TV.
• Achieved 1.6 L CH₄/L-d and 6.5 L CH₄/L_TV in the third stage, with a global energy recovery of 267.5 kJ/L_TV.

Conclusions:

• The three-stage cascade process is effective for valorizing tequila vinasse.
• The process enables high and stable biohydrogen production rates.
• Significant energy recovery was achieved through the integrated production of biohydrogen and methane.