Biochar as a soil amendment has the potential to sequester carbon dioxide from the atmosphere and improve crop yields by reducing nutrient leaching and increasing soil aeration and water holding capacity. Additional nutrients can be introduced into the soil by activation of the biochar with nutrient rich materials such as manure or digestion residues. Likewise, the anaerobic digestion performance might be affected by the biochar addition during the activation.
This study investigates the effect of municipal solid green waste derived biochar on mesophilic anaerobic digestion in terms of particle size and amount of added biochar to the digestion of microcrystalline cellulose. Both, particle size and biochar concentration, affected the methane yield and degradation kinetics. While small particles (0.125-0.25 mm) had a slight negative effect, both middle- (0.5-1 mm) and high-sized (2-4 mm) particles had a positive effect on the initial and final methane yield increasing with the concentration (1, 2.5 and 5 g L-1). The improvement of the initial methane yield could be attributed to the available colonialization area for microorganisms on the biochar, whereas the increased final methane yield was influenced by the own gas potential of the biochar. The results suggest that municipal solid green waste is a suitable feedstock for biochar production and the subsequent integration within the anaerobic digestion process chain.