Improvement in Methane Concentration in the Biogas Produced through the Co-digestion of Food Waste and Mezcal Vinasses

Abstract

The waste generated by the mezcal and seafood restaurant industries has significant negative environmental impacts on soils, water, and air. However, these waste materials offer the potential for methane production through anaerobic digestion. This research focuses on evaluating a methodological strategy that involves using an enriched inoculum, co-digesting waste materials, and applying specific pretreatment (chemical, thermal, and adjusting the volumetric ratio of residues) to produce biogas with a high methane content, as assessed through the Biochemical Methane Potential (BMP) test. The results demonstrate that the enriched inoculum used in the test exhibited a pH of 8.18, an Alkalinity of 31 g CaCO₃/L, and an alpha (α) ratio of 0.75. The BMP test was conducted over 29 days. In the most successful test, which involved pretreatment at a temperature of 50 °C, a residue ratio of 1 V_SW (Volume of Seafood Waste)/2 V_MV (Volume of Mezcal Vinasses), and a pH of 6.5, we achieved a methane production of 1420.51 ± 0.038 N mL CH₄, with a biogas containing 81.5% methane. This process also yielded 175.37 N mL CH₄ per gram of Volatile Solids (VS) and a degradation kinetic constant of 0.14 1/d. Through the methodological strategy used with the combination of an enriched and stabilized inoculum, the co-digestion of the waste for nutrient complementation, and the application of pretreatments, it was achieved that the different stages that constitute the anaerobic process allowed for the establishment of optimal conditions for the generation of biogas with a high methane content.

Graphical Abstract