Quality control causes an average of 5-7% of beer produced to be considered waste. This beer may have been left in tanks after fermentation or before packaging, tainted with unwanted flavours from trub and excess yeast, or contaminated elsewise. Like trub, this waste beer cannot be disposed of down the drain as it will increase the BOD of the water. Most commonly, this waste beer is combined with other high-strength brewing wastes in a fermentation or evaporation system. Further processing allows ethanol to be extracted and used in other products such as vinegar, alcoholic beverages, cosmetics, pharmaceuticals and tobacco. The by-products of the ethanol production can be used as flavour enhancers for soups, dressings, stocks and other food products (Priest & Stewart, 2006).