EFFECT OF FERMENTATION TIME ON BIOGAS PRODUCTION FROM WATER HYACINTH AND COW DUNG IN A SIMPLE REACTOR

The utilization of lignocellulosic biomass as a feedstock for biogas production has gained increasing attention in supporting renewable energy development and sustainable organic waste management. However, studies investigating the effect of fermentation time on the co-digestion of water hyacinth (Eichhornia crassipes) and cow dung using a simple and low-cost reactor system remain limited. In addition, the use of water hyacinth as a single substrate is constrained by its recalcitrant lignocellulosic structure and an unfavorable carbon-to-nitrogen (C/N) ratio, which may inhibit anaerobic microbial activity. This study aimed to analyze the effect of fermentation time on biogas production from the co-digestion of water hyacinth and cow dung using a simple reactor made from recycled plastic bottles. Water hyacinth was mechanically pretreated through a simple crushing process to increase substrate surface area and enhance anaerobic degradation. The substrate mixture was anaerobically fermented at ambient room temperature using a 1:1 ratio based on wet weight, consisting of 125 gr of water hyacinth and 125 gr of cow dung, with fermentation periods of 16, 19, 22, 25, and 28 days. The observed parameters included physical changes in the substrate, biogas volume, biogas yield, and flame test performance as a simple indicator of combustible gas formation. The results showed that fermentation time affected the observed biogas parameters. The substrate gradually changed from a coarse texture into a smoother and more homogeneous form as fermentation progressed. Biogas volume and yield exhibited fluctuating patterns, characterized by an increase during the early fermentation stage, a decrease on days 22 and 25, and a subsequent increase on day 28. The highest biogas volume was obtained on day 28, reaching 184.98 mL with a biogas yield of 0.73992 mL/g. Flame test observations indicated variations in flame characteristics throughout the fermentation process, whereas no flame was observed on day 25, indicating a low concentration of combustible gases. These findings suggest that fermentation time plays an important role in determining the quantity and characteristics of biogas produced and indicates the presence of a potential optimum fermentation period in the anaerobic digestion process.