Investigating the use of local brewing banana waste for biogas production.

Abstract

Biogas is a sustainable alternative for fossil fuels. This also provides a solution to bio wastes. Majority of biogas generation units use animal wastes as feed material. In Uganda the production of biogas has been adopted with large scale industries like nile brewery but has not yet been adopted by small scale ethanol producers. This study investigates the use of local brewing banana waste for biogas production. In this study batch anaerobic digestion of organic solid waste was carried out for 25 days for varying substrate. Banana brewery waste, pig litter and cow dung were collected to be used in the experiment. Characterization of the substrates was done and the substrates were mixed in different ratios. The set up consisted of a digester which was of 5 litres capacity and it was filled with 1.6kg of the mixed substrates with water in ratio of 1:1 and addition of sodium hydroxide (NaOH) in water was made to remove CO2. The volumetric yield of biogas was noted daily using water displacement method. The cumulative volume methane gas produced for 25 days was 230 ml per 1.6kg for cow dung alone, 312 ml per 1.6 kg for pig litter alone, 145 ml per 1.6 kg for banana brewery waste alone, 446 ml per 1.6kg for 75% cow dung and 25% brewery waste, 686ml per 1.6kg for 75% pig litter and 25% brewery waste, 353 ml per 1.6 kg for 25% pig litter and 75% brewery waste, 389 ml per 1.6kg for 50% cow dung and 50% brewery waste and 551 ml per 1.6kg for 50% pig litter and 50% brewery waste. In this research, it was found that the highest produced biogas was for pig manure 75% brewery waste 25%, followed by pig manure 50% brewery waste 50% and lowest was brewery waste alone. Research show that the brewery waste can be best co-digested with pig manure than it can be with cow dung and this is due to the highest value of TVS for brewery banana waste and pig manure leads to high production of biogas.