Optimisation of Biogas Production by Co-Digestion of Domestic Animal Waste

Energy plays an important role in the economic development of any country. The majority of the world’s urban population depends on non-renewable energy sources generated from burning fossil fuels. This practice has a negative effect on the environment and should be avoided. The alternative would be the provision of renewable energy sources, which are adequate, affordable, efficient and reliable. This can be generated from various sources, such as solar, wind and organic waste. When organic waste undergoes a process called anaerobic digestion, it produces slurry and biogas which are both valuable products. Slurry is a good soil conditioner for crops and vegetables while biogas is used as a source of energy. Anaerobic processes take place in an airtight sealed container called a biogas digester. Research was conducted on the possibility of mixing three different livestock wastes in a single biogas digester (co-digestion) with a view to optimising biogas production. The livestock wastes used were cow dung, pig dung and chicken droppings collected from a rural village in Limpopo Province of South Africa. Five different mix ratios were determined based on daily available individual domestic animal waste from the study area and their carbon:nitrogen (C:N) ratio, which is one of the critical factors affecting biogas production from animal wastes. The study results show that the optimum biogas production was from a mix ratio of 1:1:1 (chicken droppings: pig dung: cow dung) digested at 32°C.