Investigation of the co-digestion of cow dung with sweet potato waste and cassava waste for biogas production.

Abstract

Biogas refers the mixture of different gases produced from anaerobic digestion of organic substrates for example cow dung, agricultural wastes and so on. It is an environmentally friendly source of fuel that is methane which is converted into energy. Co-digestion is when several substrates are digested simultaneously in an oxygen free environment and this is believed to increase on the volume of methane produced according to the different researches that have been done. This can be attributed to the positive synergetic effect established in the digestion medium. There are number of substrates that give different significant volume of methane without even mixing them together. However, co-digestion does not mean increased methane volume. The objective of this research was to investigate the co-digestion of cow dung with sweet potato. and cassava wastes/peelings. The substrates used were. cow dung, sweet potato wastes/peelings and cassava peelings and a mixture of sweet potato and cassava wastes each with cow thing in different combinations and also making a three mix co-digestion. The substrates were collected, dried, sorted and crushed mechanically to form a paste to provide a favorable area for microbes’ attack. They were mixed with water in the ratio of before feeding them into the litre bottle digesters. This experiment stood for 30 days. A liquid displacement method was used to determine the volume of methane produced. The three mix co-digestion gave the highest volume of methane of 0.131itres/g -VS followed by cassava waste+cow dung with 0.11 litre/g-VS and control (cow dung alone) with 0.091itres/g-VS. Sweet potato+cowdung gave the least volume of the methane of 0.071itres/g-VS. Analysis of variance was carried out to test the treatment difference which was significant to the substrate used. However, this experiment was carried out at ambience from 23-27 0C. Research says that the higher the temperature (mesophilic range 23-400C) the more stable the microorganisms be and produce more gas within a short retention time.