A perspective on decarbonizing whiskey using renewable gaseous biofuel in a circular bioeconomy process

Abstract Low-carbon circular economy strategies within the whiskey industry necessitate minimal use of fossil-based energy including heat and electricity. Renewable energy generated from process by-products such as draff and pot ale offers opportunities for circular bioeconomy systems. However, such a system is yet to be defined and assessed in detail. In this study, biological valorization (dark hydrogen fermentation and anaerobic digestion) of whiskey by-products was comparatively evaluated in terms of fundamental principles and thermodynamics of biochemical reactions. Four scenarios based on a whiskey plant size of 2 million L/a were evaluated to determine the potential energy recovery (in the form of electricity and heat) and CO2 emissions reduction. The recommended scenario with anaerobic digestion of pretreated by-products resulted in a biogas production of 1.72 million m3 (containing 1.03 million m3 biomethane, corresponding to an energy yield of 10,300 MWh). If the produced biogas is used for producing heat and electricity in a combined heat and power system, 446% of the annual electricity demand (740 MWeh) and 25% of the heat demand (4,230 MWthh) of the traditional distillery can be covered, leading to a reduction in energy related CO2 emissions of 61% from whiskey production (2,300 ton CO2). Preliminary economic analysis shows that the proposed system has an annual net income of €741,176 with a payback period of 3.94 years. Net present value of the system is €4,933,456 with a discounted payback period of 4.77 years. Future research on a detailed techno-economic feasibility and life cycle assessment of such a system should be investigated before practical implementation.