Anaerobic co-digestion of jackfruit waste with cow dung and poultry droppings: evaluating the biogas production and agricultural re-use potential of the digestates

Abstract Jackfruit waste, though abundant in tropical regions, is underutilized due to its low biodegradability, limiting its potential for bioenergy production. This study investigated the impact of co-digesting jackfruit (JF) waste with cow dung (CW) and poultry manure (PM) on biogas production and digestate quality for use as fertilizer. Anaerobic co-digestion was conducted at 37 °C using a water bath, with five treatments: 75% JF:25% PM, 50% JF:50% PM, 75% JF:25% CW, 50% JF:50% CW, and 100% JF (control), each replicated three times. Biogas production was measured using the water displacement method, while digestate nitrogen (N), phosphorus (P), and potassium (K) contents were analyzed using calorimetric, modified Olsen-P, and flame photometric methods, respectively. Results showed that the 75% JF:25% PM mixture achieved the highest biogas yield (373.0 mL/gVS), followed by 50% JF:50% PM (339.3 mL/gVS), while 100% JF produced significantly less (82.3 mL/gVS). The 50% JF:50% PM digestate had the highest nutrient content, with N, P, and K levels of 45.44, 28.42, and 32.57 g/kg, respectively, all significantly higher than the 100% JF digestate ( p ≤ 0.05). To meet the nitrogen requirement for maize (50 kg N ha −1 ), 1.089 t of 50% JF:50% PM digestate per hectare would be needed, generating 43.2 m 3 of biogas, equivalent to 864 MJ of energy, replacing 26.78 t of firewood. The study concludes that co-digesting jackfruit waste with poultry manure and cow dung enhances biogas yield and digestate quality, supporting sustainable waste management, renewable energy, and soil fertility. Adoption of co-digestion by farmers and biogas operators should be encouraged through policies and training. Future research should focus on efficient and cost-effective pre-treatment methods to improve jackfruit waste biodegradability and process efficiency.