Biofuel co-products as livestock feed - Opportunities and challenges

403Chapter 23Co-products of the United States biofuelsindustry as alternative feed ingredients foraquacultureKamal Mjoun 1 and Kurt Rosentrater 21Alltech Biotechnology Center, Brookings, SD, United States of America2Iowa State University, Ames, IA, United States of AmericaE-mail for correspondence: karosent@iastate.eduABSTRACTThe tremendous growth of the biofuels industry has made large amounts of co-products (i.e. distillers grainand crude glycerin) available for use in aquafeeds. This chapter reviews the prospects and challenges associatedwith their use in aquafeeds. Properties of each product as it pertains to fish nutrition and available research aredescribed for different fish species. Despite the apparent deficiency in lysine and the high fibre content in DDGS,considerable amounts of DDGS can be fed to omnivorous fish species without impact on growth or product quality.Nutrient variability is, however, an issue that needs to be considered when feeding DDGS to fish. The use of crudeglycerin in fish is less clear, and further research is necessary before nutritional recommendations can be made.INTRODUCTIONHigh energy prices and government policies that encouragethe use of biofuels have spurred a tremendous growth in theethanol and biodiesel industries, both in the United Statesand internationally over the last decade. In 2005, UnitedStates total ethanol production was estimated at 15.8 billionlitres, and by early 2010, 51 billion litres of ethanol wereproduced (RFA, 2011). Similarly, biodiesel production hasincreased dramatically from 284 million litres in 2005 to 1.7billion litres in 2007 (NBB, 2007). The surge in biofuel productionhas been simultaneously accompanied by a growingsupply of co-products such as distillers grain and crude glycerin(i.e. glycerin or glycerol). Total supply of United Statesdistillers grain was estimated at 32.9 million tonne in 2010,an increase of more than 13 fold compared with 2000(Figure 1). The United States biodiesel industry is expectedto produce an estimated 640 000 tonne of crude glycerinbetween 2006 and 2015 (Nilles, 2006). Excess glycerin inthe market creates enormous marketing challenges andrequires finding new uses for this co-product. Competitivepricing of low value crude glycerin has created opportunitiesfor this co-product to be used in livestock feeding.To date, distillers grain from the dry-grind ethanolindustry have received considerable attention in animalfeeds. In contrast, glycerol has been used more in industrialapplications, although new research has shown thatglycerol appears to be a promising energy source in animaldiets. Distillers grain include traditional co-products, suchas distillers wet grains, dried distillers grain with or withoutsolubles (DDG and DDGS), and condensed distillers solubles(CDS). DDGS is the co-product that is most extensivelyproduced in the ethanol industry. Recently, fractionationtechnologies used in ethanol production have resulted innew feeds with unique chemical compositions. Also, it isimportant to note that a small fraction of distillers grainis produced from beverage distilleries. However, the contributionof distillers grain from the beverage distilleriesrepresented less than 2.7 percent of all the distillers grainproduced in 2010/11 in the United States (Hoffman andBaker, 2010). In addition, maize (corn) is the primary feedstockgrain used to make ethanol, accounting for morethan 98 percent of all DDGS produced (Hoffman and Baker,2010). Hereafter, the term “distillers grain” will refer to distillersdried grains with solubles (DDGS) (from maize) unlessotherwise noted. Currently, DDGS is fed primarily to beefand dairy cattle, swine and poultry (Figure 2). No estimateson the current use of DDGS in aquafeeds could be found,but it is expected to be very small.Another high growth sector in recent years has beenaquaculture. Aquaculture has been growing at a rapid paceof approximately 6.2 percent per annum, from 38.9 milliontonne in 2003 to 52.5 million tonne in 2008 (FAO, 2008),and currently accounts for over 50 percent of all food ofaquatic origin consumed by humans worldwide. The valueof aquaculture production was estimated at US$ 98.4 billionin 2008. However, concerns exist over the sustainability ofaquaculture for a number of reasons, one of which is theincreased pressure on feed ingredients, especially fish meal