In a dry mill, ethanol is produced from corn after several steps including grinding, slurrying, cooking, liquefaction, saccharification, fermentation and distillation. Further steps are implemented to separate coproducts such as centrifugation, evaporation and drying. From the original corn mass before processing, approximately one third results in carbon dioxide during fermentation, one third is converted into ethanol and the residue are nonfermentable compo­nents in the form of different coproducts namely dried distillers’ grains with solubles (DDGS), dried distillers’ grains (DDG), wet distillers’ grains (WDG) and condensed distillers’ solubles (CDS). The coproducts are mainly dried and sold as dried distillers’ grains with solubles (DDGS). This way, it is possible to store the coproduct for a longer time or ship it to far distances with less probability of fungi attack. A smaller part of the coproducts are shipped wet locally for immediate usage [23—24]. Distillers’ grains have been traditionally using as animal feed due to its nutritious value as shown in Table 1 [25—31]. At the end of ethanol production process, when most of the grain’s starch portion is fermented, there is an increase of 3 to 4 times in other components of the grain including protein, lipid and fibre over that contained in the uncon­verted whole grains [27].

Several attempts and studies have been published on distillers’ grains application as animal feed in many different species such as dairy cattle [32], beef cattle [33], swine [34], broiler [35], laying hen [36], turkey [37], lamb [38], catfish [39], tilapia [40], trout [41] and prawn [42]. However, four major livestock species to which distillers’ grains is practically fed are beef cattle, dairy cattle, swine and poultry [43—45]. Renewable Fuel Association (RFA) reports the distillers’ grains consumption in 2009 in different species at approximately 39% for dairy cattle, 38% for beef cattle, 15% for swine, 7% for poultry and 1% for other species [24]. The important question here is whether the increasing supply of distillers’ grains can be totally consumed by animals or the supply far exceeds its demand as feed. According to Hoffman and Baker [44] and Tokgoz et al. [46] the potential domestic and export use of distillers’ grains in U. S. exceeds its production and the U. S. beef sector is the dominant user of distillers’ grains. However, such opinions need precise consideration with respect to the fact that incorporation of distillers’ grains within animal diets exhibits some limitations. Since distillers’ grains are highly con­centrated in terms of nutritious content, it should be included as a part of animal feed. In this regard, Canadian Food Inspection Agency (CFIA) has set out the policy for the maximum inclusion rates of distillers’ grains in the feed of different species [47]. For example, the inclusion rates of distillers’ grains in the diet of beef cattle and swine must not exceed 50% on a dry basis. This suggests that continuing the use of distillers’ grains in animal diet in order to keep the track with its increasing supply from ethanol production can only come true if the number of consumer animals is also increasing. In other words, finding new value-added usages for distillers’ grains within feed sector should also be considered in the future.

It is worth to note that the U. S. dried distillers’ grains with solubles (DDGS) exports already doubled in 2009 compared to 2008 and U. S. has managed to increase its export of DDGS in 2010 by 60% compared to 2009 [48]. This may suggest that there is an excess of DDGS supply over its consumption in animal feed sector in the United States. Moreover, it should be carefully examined how the revenue from distillers’ grains sale as feed, returning to the biofuel industry will economically help the ethanol industry. For corn biofuel industry to stay viable, the applications of its coproduct, distillers’ grains, need to be expanded [23]. Consequently, the new outlets of distillers’ grains may add value to it and create revenue for the corn ethanol biofuel. Such new usages can be value-added animal [23, 49] and human food [50], burning [51—52], extraction of zein [53], cellulose [54] and oil [55—56] from distillers’ grains, and biobased filler for polymer composites, which is going to be discussed more later on.