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Article

Valorization of Vinasse and Ethanol Stillage in Bioelectrochemical Systems via Sequential Microbial Sulfate Reduction and Biomethanation

by
Anatoliy Angelov
*,
Svetlana Bratkova
,
Polina Velichkova
,
Katerina Nikolova
,
Petia Genova
,
Rosen Ivanov
and
Sotir Plochev
Department of Engineering Geoecology, Faculty of Geological Survey, University of Mining and Geology “St. Ivan Rilski”, Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria
*
Author to whom correspondence should be addressed.
Biomass 2026, 6(2), 21; https://doi.org/10.3390/biomass6020021
Submission received: 21 December 2025 / Revised: 5 February 2026 / Accepted: 3 March 2026 / Published: 5 March 2026
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Abstract

In laboratory installations, wastewater from the distillery industry (ethanol stillage and vinasse) is treated via a two-stage combination of microbial sulfate reduction (MSR) and biomethanation, assisted by bioelectrochemical systems (BESs). In the first stage, a sulfidogenic bioreactor with an integrated microbial fuel cell (MFC) is used, which partially oxidizes the produced H2S and facilitates the conversion of organic compounds. Sulfate removal reaches 95.4% (stillage) and 92.8% (vinasse), with corresponding COD reductions of 30.6% and 36.5%, respectively. The polarization curves, power density, generated current, and coulombic efficiency are analyzed. The sulfidogenic bioreactor consortium is dominated by Deltaproteobacteria, which contributes to acetate accumulation during the MSR stage. Methanogens are dominated by the genus Methanofolis. In the second stage of anaerobic digestion, three treatment options are investigated: direct biomethanation, biomethanation after preliminary MSR, and biomethanation after MSR with a microbial electrolysis cell (AD-MEC). The highest COD conversion rates are achieved in the AD-MEC variants: 91.36% for ethanol stillage and 92.8% for vinasse. Microbial communities are dominated by acetoclastic methanogens of the genus Methanothrix. For stillage treated after MSR, biogas production is nearly double that from direct methanation. For vinasse, the largest amount of biogas is generated during by the integrated MEC system, followed direct methanation. Methane content is the highest in methanation after MSR in AD-MEC (93.4–93.6%).
Keywords: ethanol stillage; vinasse; anaerobic digestion; microbial sulfate reduction; biomethanation; BES; MFC; AD-MEC; bioenergy ethanol stillage; vinasse; anaerobic digestion; microbial sulfate reduction; biomethanation; BES; MFC; AD-MEC; bioenergy

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MDPI and ACS Style

Angelov, A.; Bratkova, S.; Velichkova, P.; Nikolova, K.; Genova, P.; Ivanov, R.; Plochev, S. Valorization of Vinasse and Ethanol Stillage in Bioelectrochemical Systems via Sequential Microbial Sulfate Reduction and Biomethanation. Biomass 2026, 6, 21. https://doi.org/10.3390/biomass6020021

AMA Style

Angelov A, Bratkova S, Velichkova P, Nikolova K, Genova P, Ivanov R, Plochev S. Valorization of Vinasse and Ethanol Stillage in Bioelectrochemical Systems via Sequential Microbial Sulfate Reduction and Biomethanation. Biomass. 2026; 6(2):21. https://doi.org/10.3390/biomass6020021

Chicago/Turabian Style

Angelov, Anatoliy, Svetlana Bratkova, Polina Velichkova, Katerina Nikolova, Petia Genova, Rosen Ivanov, and Sotir Plochev. 2026. "Valorization of Vinasse and Ethanol Stillage in Bioelectrochemical Systems via Sequential Microbial Sulfate Reduction and Biomethanation" Biomass 6, no. 2: 21. https://doi.org/10.3390/biomass6020021

APA Style

Angelov, A., Bratkova, S., Velichkova, P., Nikolova, K., Genova, P., Ivanov, R., & Plochev, S. (2026). Valorization of Vinasse and Ethanol Stillage in Bioelectrochemical Systems via Sequential Microbial Sulfate Reduction and Biomethanation. Biomass, 6(2), 21. https://doi.org/10.3390/biomass6020021

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