Biogas production from co-digestion of water hyacinth, banana peel and water spinach wastes using a horizontal anaerobic digester

Biogas is an alternative energy source that can replace fossil fuels. The residue of agricultural products in the form of water hyacinth, fruit, and vegetable waste is a source of an organic material having large cellulose, lignocellulose, and lignin content so that it has the potential as a raw material for biogas production. This study proposed to evaluate the influence of the composition of the mixture of water hyacinth (WH), banana peel (BP) and water spinach (WS) wastes to biogas production using a horizontal anaerobic digester. At the initial experiment, the amount of cow dung mixed with water at a mass ratio of 1:1 was introduced to the horizontal anaerobic digester as a starter and was incubated for 5 days. Furthermore, the raw material of WH, BP, and WS wastes was crushed/ground at a size of 1 cm. Two kg of mixed water hyacinth, banana peel, and water spinach with a mass ratio of 100 : 0 : 0 (WH), 0 : 50 : 50 (BP-WS) and 50 : 25 : 25 (WH-BP-WS) was mixed with water to a volume of 8 L and was fed per day into the horizontal anaerobic digester. The biogas output from the anaerobic digester was collected in tubular plastic, and the volume of biogas was measured using the displacement of water. The results showed the highest average yield of biogas production was 0.3145 ± 0.1 l/gVS.day with cumulative biogas of 620.368 l, and the lowest one obtained by WH-BP-WS (0.2463 ± 0.1 l/gVS.day) with cumulative biogas of 402.012 l. While for mono digestion of WH, biogas yield was 0.260 ± 0.1 l/gVS.day with cumulative biogas of 518.768 l. The composition of biogas showed the use of BP-WS produced CH4 (71.23%), CO2 (25.79%), H2S (1.71%) and NH3 (0.39%); WH-BP-WS was CH4(71.97%), CO2 (25.91%), H2S (1.68%), NH3(0.38%); while for WH was CH4 (70.97%); CO2(26.77%), H2S (1.37%), NH3(0.61%), respectively.