Methane Production Using Brewery Spent Grain: Optimal Hydrothermolysis, Fermentation of Waste and Role of Microbial Populations

• Published in: Waste and biomass valorization 2022-02, Vol.13 (2), p.1179-1194
• Main Authors: Gomes, Marina Mauro, Rabelo, Camila Abreu B. Silva, Sakamoto, Isabel Kimiko, Silva, Edson Luiz, Varesche, Maria Bernadete Amâncio
• Format: Article
• Language: English
• Subjects: Acetic acid; Acids; Archaea; Breweries; Butyric acid; Engineering; Environment; Environmental Engineering/Biotechnology; Fermentation; Hydrolysates; Industrial Pollution Prevention; Metabolites; Methane; Methanogenesis; Microorganisms; Original Paper; Propionic acid; Renewable and Green Energy; Renewable energy; Waste Management/Waste Technology
• ISSN: 1877-2641; 1877-265X
• DOI: 10.1007/s12649-021-01564-1

The hydrothermolysis variables temperature (150–210 °C) and time (10–20 min) were assessed to improve hydrolysis efficiency of brewery spent grain (BSG) for renewable energy generation. The intensification of the pretreatment was expressed by the severity variation (2.8–4.5) and the process was optimized with methane production of 411.6 ± 7.2 mL g −1 TVS (severity 4.2). The fermentation-methanogenesis of BSG and hydrolysate resulting from BSG hydrothermolysis process under severity of 4.2 (210 °C for 10 min) was evaluated by central composite design with the variables operation temperature (30–60 °C), BSG concentration (7.3–20.7 g L −1 ) and hydrolysate (0–12.4 mL). The higher methane production observed was 305.8 mL g −1 TVS, with 14 g L −1 of BSG, without hydrolysate at 45 °C. The main soluble metabolites were acetic acid (233.17 mg L −1 ) and butyric acid (156.0 mg L −1 ). On other hand, the lower methane production (108.5 ± 2.0 mL g −1 TVS) verified was 14 g L −1 of BSG, 6.5 mL of hydrolysate at 60 °C, which revealed that in this condition propionic acid (947.4 mg L −1 ) and acetic acid (599.2 mg L −1 ) were expressive. In the optimal fermentation-methanogenic condition of pretreated BSG, Macellibacteroides and Sphaerochaeta (15.9 and 14.7%, respectively) were identified, as well as archaea similar to Methanosaeta (80.4%), favoring the acetoclastic methanogenic pathway. Graphic Abstract