Chapter 34 Co-products from malt whisky production and their utilisation J. C. AKUNNA 1 AND G. M. WALKER 2 1 Urban Water Technology Centre, and 2 Yeast Research Group, School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, United Kingdom Email: j.akunna@abertay.ac.uk and g.walker@abertay.ac.uk INTRODUCTION Environmental sustainability and greenhouse gas (GHG) mitigation are two of the greatest challenges currently facing the global distilled spirits industry. Regulatory bodies around the world are in the process of placing stretching environmental targets upon domestic distilled spirits production. For example, the Scotch Whisky Association’s environmental strategy has placed environmental targets upon the industry as a whole, including GHG mitigation, improved energy efficiency and specific renewable energy utilisation targets of 20% by 2020, rising to 80% by 2050 (Scotch Whisky Association 2012). In light of this, the area of environmental sustainability and renewable energy utilisation is one of intense research interest. There is significant opportunity to contribute to environmental targets through the utilisation of co-products in the generation of bioenergy. This approach has a several potential advantages, those being greenhouse gas (GHG) mitigation through the substitution of conventional fuel sources (e.g. gas and heavy fuel oil) with those of a renewable nature, alongside a reduction in discharges to the local environment. This Chapter discusses the production, characterisation, management and utilisation of co-products from malt whisky distilleries. CO-PRODUCTS AND THEIR PRODUCTION The Scottish distilling industry typically generates three main types of co-product - spent grains (SG), pot ale and spent lees, with each being generated during different stages of the production process. Production of Scotch whisky usually involves six distinct production stages - with mashing and distillation being the key stages in terms of co-product production. Figure 1 outlines the production of Scotch malt whisky and the process locations that generate co-products. Malt whisky distilleries in Scotland produce spirit which is derived from a mash that comprises 100% barley malt. The grist, or milled malt, is fed to a mash vessel (traditionally called the “mash tun”) and mixed with water (about 4 parts water to 1 part grist) which is heated to maintain a final temperature of around 65°C (Barnes and Andrews, 1998). The mix is then fed into the mash tun and thoroughly mixed for about 20 minutes before being allowed to stand for about 1 h. During this time amylase and protease enzymes within the malted barley convert starch and protein to fermentable monosaccharides (mainly glucose, maltose and maltotriose) and amino acids, respectively. Subsequently the first worts (sugar-rich liquid extract) are drained through the mash bed (comprising the grist) until it is almost dry. A malt distillery continues to add water after the first worts 34-Akunna.indd 1 21/07/2016 18:32:56