Inoculum Adaptation for the Anaerobic Digestion of Mezcal Vinasses

Abstract

Vinasses are a very harmful residue of the alcohol distillation, their discharge into soil and water can cause negative environmental impacts if the appropriate treatments do not take place. Anaerobic digestion has shown to be the best technological and economical method to treat this residue, thus bioenergy can be generated as by-product of this process. Nevertheless, the slow adaptation of the microbial consortium in inoculum (activated sludge) to the substrate (mezcal vinasses) is very important to enhance the efficiency of the biogas and methane production, as well as organic matter removal. In this work, the adaptation process of the anaerobic digestion of mezcal vinasses was carried out in a 30-day period. Inoculum (activates sludge) and vinasses were mixed initially at the ratio 7:3. The feeding steps were done every seven days replacing 30 % of the total volume with new vinasses. Biogas was quantified and qualified. Biogas production reached 217 L/kgVSvinasses generating a daily methane content between 50 and 55 % by the end of the adaptation period. The organic matter removal efficiency was almost seven times higher at the end of the adaptation, in comparison to the beginning. This suggests that a slow adaptation process enhance the organic matter removal and eventually other pollutants in vinasses. When comparing this results with the literature, biogas and methane production were similar, nevertheless the anaerobic digestion could be optimized, in order to increase the methane content in biogas and the removal rate of organic matter. Palabras clave: biogás, demanda química de oxígeno, FOS/TAC, metano RESUMEN Las vinazas son un residuo proveniente de la destilación de alcohol, su descarga en suelos y aguas puede causar impactos ambientales negativos si no se realizan los tratamientos adecuados antes de considerar su descarga. La digestión anaerobia ha demostrado ser un método con ventajas tecnológicas y económicas para tratar este residuo y generar bioenergía al mismo tiempo. Sin embargo, una lenta adaptación del consorcio microbiano contenido en el inóculo (lodo activado) al sustrato (vinazas

Uso de vinazas de mezcal para producir metano por co-digestión con estiércol de bovino

“…On the other hand, bovine manure addition to the mixture increased pH to a methanogenic level. The vinasses pH was comparable to that reported by other researchers for mezcal vinasses with values between 3.5 and 4.77 (Gómez-Guerrero et al, 2019;López-Velarde et al, 2019). The initial pH of the mixtures studied was at optimal levels for anaerobic digestion (6.8 and 7.4), except for the 100-0 mixture with 5.49, which is closest to the optimal pH level of acidogenic bacteria, between 5.5 and 6.5 (Khanal, 2009).…”

“…The total solids content of vinasses studied was similar to those obtained from industrial-type mezcal factories in Oaxaca (43.4 g L -1 ) (Villalobos et al, 2009) and San Luis Potosí (49.17 g L -1 ) (López-Velarde et al, 2019), but lower than artisan-type factories (91-94.7 g L -1 ) (Gómez-Guerrero et al, 2019). In contrast, the volatile solids content of vinasses was lower than those from artisan-type mezcal factories (72 g L -1 ) (Gómez-Guerrero et al, 2019) and Comiteco liquor vinasses (62.90 g L -1 ) obtained from agave juices (Cruz-Salomón et al, 2017).…”

“…The 100-0 mix produced an intermediate methane volume (Figure 2). initial total present in the juice of the cooked agave "piñas" (Vera-Guzmán et al, 2009), and 51 mg g -1 of total sugars in vinasses after distillation (López-Velarde et al, 2019). These sugars present in vinasses, along with other suspended organic solids (Espinoza-Escalante et al, 2009), are used by bacteria during anaerobic digestion to obtain energy and forward substrates for methanogenesis.…”

“…Zelaya-Benavidez et al: Biotecnia / XXIV (2): 53-58 (2022) utilizing nutrient balance and improvement of the medium buffer capacity (Akyol et al, 2016); i.e., the co-digestion of cow dung and maize waste in batch reactors improved the biogas yield by 92 % when a 10:5 cow dung:maize waste ratio was used compared with a 10:1 ratio (Abdoli et al, 2014); the co-digestion of llama (Lama glama), sheep (Ovis orientalis aries), and cattle (Bos primigenius taurus) manures in a semi-continuous system increased methane yield by more than 50 % compared to only llama manure (Álvarez and Lidén, 2009). López-Velarde et al (2019) improved the buffer capacity of the mixture by using activated sludge at a pH of 7 to evaluate vinasses adaptation to inoculation in a semi-continuous flow reactor; they obtained up to 85.5 mL CH 4 g -1 volatile solids (VS) of vinasses. However, some doubts remain, especially when the vinasses content in mixtures increases.…”

Improvement in methane concentration in the biogas produced through the co-digestion of waste from the seafood restaurant industry and mezcal vinasses.

“…This means that C, N, and P are all important nutrients for AD [24,25]. (control of the inoculum), which did not generate biogas, attributable to the absence of food, caused the inhibition of the microorganisms [29].…”