Design Analysis and Production of Biogas Using Local Feedstock “Elephant Grass”

Abstract

The study was aimed at constructing a biodigester and determining the efficiency of using a mixture of cow dung and elephant grass as feedstock for biogas production. The volume of the biodigester was 126 litres (0.126m3) and it was constructed using mild steel with a thickness of 5mm and a maximum allowable stress of 1.74 N/mm2 to withstand high pressures that could be generated within the digester. 6 kg of elephant grass was mixed with 6 kg of cow dung and 12 litres of water and poured in the biodigester and left for a period of 21 days with a temperature range of 35°C - 44°C. Graphs of temperature (°C) against retention period (days) and daily biogas produced (litres) against retention period (days) were obtained. The daily biogas yield was measured by calculating the volume increase of the storage device which is a car tyre tube in this case. Elephant grass serves as an effective substrate for biogas production. To enhance its efficiency in the digester, it is recommended to mechanically pre-treat the grass by breaking it into smaller particles.