A feasibility study to optimise extraction of bio-based materials following fermentation of distillery waste

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Pot-ale is the principal effluent co-product of the whisky industry and is produced in copious quantities with between 8.5 -10 litres of pot-ale being created for each litre of manufactured whisky. Treatment technologies have largely been restricted to applying heat to pot-ale to create a molasses type syrup or energy extraction via AD to create heat and electricity. A Zero Waste Scotland report suggested that up to 2 billion litres of pot-ale could be available for bio-refining.Laboratory research has demonstrated that a secondary fermentation process is capable of producing a valuable class of compounds known as 'volatile fatty acids'(VFAs). Chief amongst these is hexanoic acid, a C6 short-chain acid which has numerous uses across a wide range of industries, including food, pharma, cosmetics and plastics. World supplies of hexanoic acid are largely derived from palm oil which is predominantly grown in South-East Asia. The carbon footprint for world hexanoic acid production is estimated to be in excess of 37M tonnes/CO2eq. per annum.Work undertaken with the Bio-Renewables Development Centre (BDC) is currently in the process of identifying hexanoic acid producing bacteria from samples of AD digestate. The task is now to extend this research and undertake a feasibility study to determine how to best extract and store VFAs from the fermentation mixture. The results will then establish the cost profile for this element within the overall process. This is an important step in determining process optimisation and informing the financial decision to commit substantial funds to full sized plant.