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Assessment of the effects of biochar on biogas production during anaerobic digestion of aqueous pyrolysis condensate: A circular economy approach

Abstract:

Pyrolysis of biomass leads to the production of bio-oil, non-condensable gas and biochar. Although all products have applications in the value chain, the aqueous phase of the bio-oil is a secondary waste of low value, acidic and with a complex chemical composition. This study focuses on the utilisation of the aqueous phase, termed aqueous pyrolysis condensate (APC) for energy generation via anaerobic digestion in the presence of biochar derived from the digestate to moderate the inhibitory effects of the phenolic components, thereby following the path of circular economy. Isotherm studies of the biochar showed that it had an adsorption capacity of 39.77 mgphenol.g−1biochar. The addition of biochar allowed for an 83% increase in cumulative biogas production at the highest APC loading, accompanied by an increase in CH4/CO2 ratio. This shows that the APC can be utilized as a precursor for energy generation.