Biochar enabled syntrophic action: Solid state anaerobic digestion of agricultural stubble for enhanced methane production

In this study, effect of hardwood biochar on solid state anaerobic digestion of wheat straw has been investigated. The concentration of biochar was 5, 10, 15, 20, 25 and 30 g/L and added in inoculum along with wheat straw for anaerobic action. Results showed that 10 g/L of hardwood biochar led to 2-fold increment in methane yield (223 L/kg VS) compared to the control (110 L/kg VS). However, increasing the concentration of hardwood biochar did not help in significant increase in methane yield and raised pH and alkalinity up to 8.3 and 24.3 g/L respectively. Principal component analysis showed that methane yield is positively correlated with volatile solid reduction while biochar loading is directly correlated with pH as well as alkalinity and inversely correlated with total volatile fatty acid. This study revealed that biochar may help to maintain syntrophy in the anaerobic reactor and enhance methane yield significantly.