Evaluation of biogas production from water buffalo (Bubalus bubalis) manure under tropical climate conditions

In this study, we evaluated the feasibility of water buffalo (Bubalus bubalis) manure as a substrate for biogas production under tropical environmental conditions in southeastern Mexico. The manure was collected from a livestock unit in Chiapas and processed in a 64 m3 lagoon-type anaerobic digester. The substrate was characterized through proximate and elemental analyses, and its chemical formulas and theoretical biogas composition were estimated. Additionally, physicochemical parameters (pH, oxidation-reduction potential (ORP), electrical conductivity (EC), total dissolved solids (TDS), and chemical oxygen demand (COD)) and biogas composition (CH₄, CO2, H2S) were monitored throughout the study. Our results indicated that buffalo manure exhibits favorable properties for anaerobic digestion, with high moisture content (>80%), adequate volatile solids, and adequate carbon and nitrogen contents. Over 14 weeks of operation, the system maintained stable conditions of pH (7.7–8.0) and redox potential (−180 to −280 mV), reflecting an efficient transition toward the methanogenic phase. COD removal efficiency reached 86.6%, with a degradation constant of k = 0.147 week−1. The biogas produced showed a stable CH₄ content (58–60% v/v) and low H2S concentrations (