Authors: Nweke James, Emenike Wami, Awajiogak Anthony Ujile, T.O. Goodhead
Abstract: This study investigates biogas production from water hyacinth (Eichhornia crassipes) through anaerobic co-digestion with cow dung in order to enhance methane yield and process stability. Experiments were conducted in 18.9 L batch digesters operated at 75% working volume, an organic loading rate of 3.5 g VS L⁻¹ day⁻¹, and a hydraulic retention time of 70 days under mesophilic conditions (29–38 °C). Six feedstock configurations were evaluated, comprising mono-digestion of water hyacinth and five water hyacinth–cow dung co-digestion ratios. Mono-digestion of water hyacinth produced 42.3 L kg⁻¹ VS, while the optimal 2:1 water hyacinth–cow dung ratio achieved the highest cumulative biogas yield of 54.9 L kg⁻¹ VS, representing a 29.8% increase. Biogas upgrading using a three-stage purification system (ferric oxide, sodium hydroxide, and silica gel) increased methane concentration from 60.05% to 86.02%, yielding a calorific value of 31.46 MJ m⁻³. Kinetic modelling based on coupled first-order hydrolysis and Monod microbial growth equations showed excellent agreement with experimental data (R² = 0.984, RMSE = 0.263 L). The results demonstrate that anaerobic co-digestion of water hyacinth with cow dung provides an efficient, environmentally sustainable pathway for renewable energy generation while simultaneously addressing aquatic weed management challenges.
