The alcoholic beverages industry generates vinasses, a liquid waste by-product. Tequila vinasses have a high content of organic matter (28–100 g COD/L and 13–60 g BOD5/L), low pH (3–5 units), and toxic compounds, which made difficult its biological treatment. However, this by-product can be considered for bioenergy production. A novel one-step hybrid bioreactor with suspended and attached biomass was assessed in terms of its hydrogen (H2) and methane (CH4) production from tequila vinasses. Additionally, the microbial composition of each kind of biomass was determined. The bioreactor was divided into two zones: (i) external zone with biofilm attached to a volcanic rock packed-bed and (ii) internal zone with the growth of suspended biomass. It was operated with a retention time (RT) of 6.9 days, an organic loading rate (OLR) of 2.2 ± 0.4 kg COD/m3 day and a pH between 6.5 and 6.9. Under these conditions, the reactor presented a very stable COD removal efficiency of 43 ± 11% an increase of volatile fatty acids (VFA) concentration from 2,083 to 4,902 mg/L and the biogas produced by the system was biohythane with a content of 79% hydrogen and 11% methane, which is a new report in one-step treatment systems. H2 and CH4 production rates (PR) and yields obtained were equal to 5.7 mmol H2/g CODremoved, 126 NmL H2/L day, and 10.7 NmL CH4/L day. The biofilm and suspended biomass were composed mainly by Clostridium (42 and 43%, respectively) and Bacteroides (21 and 4%, respectively). Only Methanosarcina (9%) was identified in the biofilm. This bacterial composition community corresponds to a new report since for anaerobic treatment of tequila vinasses the presence of Clostridium, Bacteroides, and Methanosarcina simultaneously had not been previously reported. The content of hydrogen (79%) and methane (11%) in the biogas, the COD removal efficiency (43%) and the biomass composition (64% of fermenters and 9% of methanogens) confirmed that this novel reactor configuration and operation allows principally a dark fermentation and some methanogenesis processes, favoring the biohythane production in a one-step system.
- Dark fermentation
- One-stage anaerobic digestion
- Suspended and attached biomass reactor