Partial Restriction. Restriction lift date: 2025-12-31
Decarbonisation of whiskey distilleries in a circular economy: investigating biorefinery systems for valorisation of distillery by-products
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Date
2024
Authors
Hackula, Anga Awonke
Journal Title
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Publisher
University College Cork
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Abstract
Decarbonisation of industrial processes is necessary to mitigate the detrimental impacts of anthropogenic climate change. Innovative technological solutions are sought that will allow for both a reduced carbon footprint and increased security of supply. The whiskey production industry produces by-products that are currently used linearly for animal feed. This thesis examines the use of by-products generated from whiskey production to enact a circular economy philosophy, which may be of further benefit to a distillery. This was achieved by examining various technologies, namely anaerobic digestion (AD), dark fermentation, and pyrolysis, in a cascading biorefinery concept.
Central to the evaluation of the whiskey by-product valorisation through anaerobic digestion was the development of a novel two-phase anaerobic digestion system, termed a leach bed reactor – expanded granular sludge bed (LBR-EGSB). Several design modifications, including the implementation of a cost-effective siphon-actuated leachate attenuation system, advanced the configuration beyond comparable designs. The LBR-EGSB could successfully convert the by-products into volatile fatty acids (VFAs) and methane-rich biogas (75 %vol). The LBR-EGSB was compared to traditional anaerobic digesters for energy production capabilities, showing similar biomethane potential, which could satisfy approximately 44 % of the thermal energy demand of a large distillery operating in Ireland.
Furthermore, the research investigated the potential of a biorefinery utilising dark fermentation, whereby the whiskey by-products were converted into biogenic carbon dioxide for use in beer carbonation, biohydrogen for use as transport or heating fuel, and VFAs for use as bioplastic beer packaging. A 50 million-litre whiskey distillery could satisfy approximately half of the carbon dioxide requirement of the Irish brewing industry. Biohydrogen was found to be best suited as a transport fuel. The VFAs could be processed into bioplastics which could completely satisfy beer packaging demand in Ireland.
Continuous VFA production and demand-driven biogas production to generate electricity during peak demand hours were also evaluated. The systems analysed were a two-phase continuously stirred tank reactor (CSTR) and the designed LBR-EGSB. Both systems exhibited continuous VFA production (up to 10.4 g. L-1Leachate) and rapid biogas production, achieving peak biogas flow rates within 30 minutes. A theoretical evaluation of processing butyric acid into biobutanol, to be blended with diesel, could produce a more sustainable transport fuel than diesel, reducing distillery-associated transport emissions by 16 %. Additionally, the novel use of whiskey barrel-derived biochar was compared to commercial carbonaceous materials, revealing its efficacy in enhancing biohydrogen and biomethane production by 15% and reducing methane production lag time, thereby advancing the understanding of pyrolysis parameters' impact on anaerobic digestion.
Overall, this thesis demonstrates that integrating AD systems, biochar application, and innovative biorefinery concepts can significantly enhance the sustainability of whiskey distilleries, proposing a pathway for modern circular economy strategies and decarbonisation of the whiskey distillery industry.
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Keywords
Anaerobic digestion , Circular economy , Volatile fatty acids production , Two-phase anaerobic digestion , Biogas production , Industrial decarbonisation , Biochar production , Biochar , Pyrolysis , Demand-driven biogas , Dark fermentation , Biohydrogen , Biogenic carbon dioxide , Biohythane
Citation
Hackula, A. A. 2024. Decarbonisation of whiskey distilleries in a circular economy: investigating biorefinery systems for valorisation of distillery by-products. PhD Thesis, University College Cork.