Anaerobic Co-digestion of Cow Dung and Food Waste for Enhanced Biogas Production and Digestate Valorization as a Soil Amendment

Abstract

The potential of organic wastes like cattle dung (CD) and food waste (FW) to produce renewable bio-gas from anaerobic digestion (AD) was investigated using three small batch digesters under 30 days of retention time. The treatments included anaerobic digestion of CD alone, anaerobic digestion of FW alone and anaerobic co-digestion of CD and FW at equal weight ratios). Biogas production, gas composition and calorific value were measured using air pressure gauge, Orsat and bomb calorimeter, respectively. The findings showed that co-digestion of CD and FW produced the highest cumulative biogas (mean = 2.149 bar) which was significantly higher than FW (mean = 1.271 bar) and CD (mean = 0.997 bar). The gas composition shows that co-digestion (CD+FW) had the highest methane content (71.2%) followed by CD (66.6) and FW (61.8). Similarly, the highest calorific value was for co-digestion (480 kcal/m³) then for FW (378 kcal/m³) and CD (345 kcal/m³). One-way analysis of variance (ANOVA) indicated that the means of gas yield were significantly different (F = 10.824, p = 0.00016). The findings indicate that anaerobic co-digestion can be a sustainable, affordable and environmentally sustainable alternative to fossil fuels and fuelwood, particularly in rural areas of developing countries. The co-digestion digestate was rich in nutrients (nitrogen, phosphorus, and potassium) and could be used as a fertilizer to enhance crop productivity in low-input farming systems.