Investigating the effects of whiskey-barrel derived biochar addition to anaerobic digestion at a distillery: A study on energy yield and system efficiency

Closed-loop systems enable circular economy systems and applications in the food and beverage sector to enhance decarbonisation. Whiskey distillation by-products are amenable to anaerobic digestion and thus facilitate resource recovery and circularity. Furthermore, biochar derived from whiskey barrels can be used as a carbonaceous additive within anaerobic digestion to enhance biomethane production. In this paper, biochar produced from the pyrolysis of discarded whiskey barrels at 300 °C, was shown to enhance biomethane production by up to 15 %. A kinetic analysis revealed that the biochar reduced the biomethane lag time by up to 42 %. The mass and energy balance of this integrated anaerobic digestion-pyrolysis system was evaluated. The overall system efficiency was assessed at 68 % of all input energy (expressed on a primary energy basis); utilisation of renewable electricity could increase this efficiency to 71 %. Biochar from discarded whiskey barrels can provide a decarbonisation pathway for whiskey distilleries but may be constrained by the total resource available.