Modelling of a Portable Decentralised Anaerobic Digester for the Production of Biogas from Cattle Dung and its Analysis using GCMS

Modelling and development of decentralized anaerobic digestion systems are the key to enabling small-scale and on-site biogas production from organic waste. A portable decentralised anaerobic digester was modelled, fabricated, and experimentally analysed with respect to biogas generation using cattle dung as the main substrate. The digester model was constructed with a plastic bottle reactor with an intravenous (IV) tubing kit built in to allow control of the gas collection. Fresh cattle dung mixed with water to become a homogenous slurry and introduced into the digester, which was airtight sealed using wax in order to keep anaerobic conditions and prevent gas leakage. The system was run under ambient conditions, with incubation time varying from 30 to 90 days with respect to the weather. Biogas generation was first verified by fire by the flame test, in which the presence of combustible gas is observed. The produced biogas was further characterized with the help of gas chromatography-mass spectrometry (GC-MS). The total ion chromatogram (TIC) showed the presence of several volatile and semi-volatile compounds such as dimethylamine, 1-octadecanethiol and tetradecanoic acid and other aliphatic and sulfur-containing compounds related to anaerobic microbial degradation during anaerobic digestion. The modelling and experimental validation show that the developed portable decentralised digester has the ability for effective biogas production through a simple and low-cost configuration. The proposed system provides a viable solution to decentralized renewable energy production and organic waste treatment. Furthermore, the study contributes to the United Nations Sustainable Development Goals, particularly SDG 3 (Good Health and Well-being) through improved sanitation, SDG 7 (Affordable and Clean Energy) by enabling renewable biogas production, and SDG 9 (Industry, Innovation and Infrastructure) by promoting innovative and scalable digestion systems.