Optimization of Biogas Production from Avocado Fruit Peel Wastes Codigestion with Animal Manure Collected from Juice Vending House in Gimbi Town, Ethiopia

Anaerobic bio digestion of fruit peel wastes is one of the potential for biogas production which subsequently reduces environmental pollution. In order to test the biogas potential of avocado fruit peel wastes co-digested with either cow dung or poultry manure, the raw materials were collected from juice vending house, dairy farm, and poultry farm, respectively. A finely grinded avocado fruit peel wastes was prepared for the different setups. The experiments include 100% avocado fruit peel wastes (T1), 100% poultry manure (T2), 100% cow dung (T3), 50% T1+50% T2 (T4), 50% T1+50% T3 (T5), 75% T1+25% T2 (T6) and 75% T1+25% T3 (T7). The total weight of the raw material was 100 g either solely or in mixture with the animal manure. 15 ml of rumen fluid collected from slaughterhouse was added into each treatment as inoculums. The total volume of the biodigesters was made 1800 ml by adding distilled water; and the setups were completely sealed in plastic bottles. The gas produced was estimated by water displacement method. Feedstocks containing both 100% poultry manure (T2) and 50% poultry manure (T4) attained maximum biogas production within 3-4 days of incubation. The highest in cumulative biogas was produced from the two treatments at 20thday. The optimum temperature, salt and pH for biogas production from the fruit wastes co-digested with animal manure were 25°C, 0.5% and 7 respectively. Under this environmental condition, the highest biogas (453.5 ± 0.5 mL) was produced by T6 that was significantly higher than the othertreatments. In general, the feed stock containing poultry manure co-digested with avocado fruit waste was fast and high in biogas generation. Therefore, co-digestion of avocado fruit peel waste with animal manure is a good strategy to produce bioenergy and minimize urban solid wastes discharge although it demands controlling some physical parameters.