Optimizing feed composition for improved methane yield during anaerobic digestion of cow manure based waste mixtures

This study investigated methane yield via anaerobic digestion of multi-component substrates based on mixtures of biodegradable single-component substrates with cow dung as main component. Bench and full-scale digestion experiments were carried out for both single and multi-component substrates to identify the relationship between methane yield and substrate composition. Results from both bench- and full-scale experiments corresponded well and showed that using multi-component substrates increases the methane yield much more than what would be expected from digestion of single substrates. Process stability as indicated by gas production, pH and NH4+ concentration variations were also improved by using multi-component substrates compared to digestion of single-component substrates. The results, thus, suggest that assessment of methane yield for multi-component substrates cannot reliably be based on methane yields for corresponding single-component substrates but should instead be measured directly.