A value-added mechanism in optimising biogas production with biochar pyrolysis products

While biogas stands a greater chance in substituting fossils fuels and contributing to the reduction of GHG emissions, its major setbacks still rely on its effective price compared to that of fossil fuels in the world market. Its production efficiency and related operational cost can give it a true competitive meaning to fossil fuels regarding upgrading and logistic cost of handling digestate. This study was aimed at investigating the possibility and the extent to which biochar could be used in optimising biogas production with biochar as a pyrolysis product. Two separate experiments were conducted during which the additions of varied quantities of low temperature (500°C), wood-based-biochar were added to anaerobic digestion of lignocellulose biomass (Phragmites australis) at the same inoculum to substrate ratio. It was observed that biochar additions at ratios of 1:1, 1:2, and 1:3 [inoculum: biochar] l/g had a positive effect in stimulating microbial activity which increased biogas production and methane concentrations. The additions were found to improve specific methane yields compared to normal feedstock mixed with inoculum. Furthermore, the biochar addition with the highest effectiveness was 0.5g (1:1) while the dose of 2g and 4g generally limited production of biogas with 4g resulting in a higher inhibition compared to 2g additions of biochar. It was concluded that biochar could play an effective role as a microbial growth stimulating agent (MGSA) in anaerobic digestion. It was also proposed that reusing biodigestate in biochar-based pyrolytic systems to enhance post biochar products could offer solutions to logistic and storage costs of biodigestate to add value in commercialisation of digestate.