Biofuel co-products as livestock feed - Opportunities and challenges

An outlook on world biofuel production and its implications for the animal feed industry 3global crude oil productive capacity coupled with growingdemand, particularly in developing nations, has led to highercrude oil prices in recent years. As such, biofuels froma variety of feedstocks have become more economicallycompetitive with petroleum-based fuels. Long-term energysupply and demand forecasts generally indicate sustainedincreases in world crude oil prices (U.S. EIA, 2011), suggestingimproved economic competitiveness for biofuels. Ifglobal crude oil prices remain at historically elevated levels,and if feedstock prices decline from the weather-relatedhighs of 2010/2011, biofuel production in many countriescould exceed the volumes specified by national policies anddirectives based purely on its economic competitivenesswith petroleum-based fuels (Hayes, 2008).COMMON BIOFUELS, FEEDSTOCKS ANDCO-PRODUCTSTwo biofuels – ethanol (ethyl alcohol) and biodiesel fromfatty acid methyl esters – account for the vast majority ofglobal biofuel production and use today. These biofuels aremade today primarily from agricultural commodities, suchas grain and sugar (ethanol) and vegetable oil (biodiesel).Significant research and development efforts are under wayto commercialize new biofuels (e.g. butanol) and new feedstocks(e.g. cellulosic agricultural residues, municipal solidwaste, algae, etc.) (Solomon, Barnes and Halvorsen, 2007).However, these “next generation” feedstocks and biofuelsare unlikely to be produced in quantity in the short termaccording to most projections (U.S. EIA, 2011). Further, theco-products from many of these new feedstocks are notlikely to have applications in the animal feed market, atleast initially. Thus, the primary focus of this paper is on currentethanol and biodiesel feedstocks and the co-productsthat result from common processing methods.Ethanol feedstocks and processesEthanol is a petroleum petrol replacement produced todaymainly from grains and sugar cane. Other less commonfeedstocks include sugar cane and beet molasses, sugarbeets, cassava, whey, potato and food or beverage waste.In 2010, approximately 87 billion litres (23 billion gallons)of ethanol were produced, with the United States, Brazil,and the European Union accounting for 93% of this output(RFA, 2011a).GrainsGrains such as maize, wheat, barley and sorghum are commonfeedstocks for ethanol production, and to a lesserextent are also rye, triticale, sorghum [milo] and oats. Thegrain ethanol process is generally the same for all of thesegrain feedstocks, though there are some slight differencesand the co-product characteristics vary somewhat dependingon the grain used.Two processes are primarily used to make ethanol fromgrains: dry milling and wet milling. In the dry milling process,the entire grain kernel typically is ground into flour (or“meal”) and processed without separation of the variousnutritional component parts of the grain. The meal is slurriedwith water to form a “mash”. Enzymes are added tothe mash, which is then processed in a high-temperaturecooker, cooled and transferred to fermenters where yeastis added and the conversion of sugar to ethanol begins.After fermentation, the resulting “beer” is transferred todistillation columns where the ethanol is separated fromthe residual “stillage”.The stillage is sent through a centrifuge that separatesthe solids from the liquids. The liquids, or solubles, are thenconcentrated to a semi-solid state by evaporation, resultingin condensed distillers solubles (CDS) or “syrup”. CDSis sometimes sold direct into the animal feed market, butmore often the residual coarse grain solids and the CDS aremixed together and dried to produce distillers dried grainwith solubles (DDGS). In the cases where the CDS is notre-added to the residual grains, the grain solids productis simply called distillers dried grain (DDG). If the distillersgrain is being fed to livestock in close proximity to the ethanolproduction facility, the drying step can be avoided andthe product is called wet distillers grain (WDG). Becauseof various drying and syrup application practices, there areseveral variants of distillers grain (one of which is calledmodified wet distillers grain), but most product is marketedas DDGS, DDG or WDG.Some dry-mill ethanol plants in the United States arenow removing crude maize oil from the CDS or stillage atthe back end of the process, using a centrifuge. The maizeoil is typically marketed as an individual feed ingredient orsold as a feedstock for further processing (e.g. for biodieselproduction). The co-product resulting from this process iscolloquially known as “oil extracted” DDGS or “de-oiled”DDGS. These co-products typically have lower fat contentthan conventional DDGS, but slightly higher concentrationsof protein and other nutrients.A very small number of dry-mill plants also have thecapacity to fractionate the grain kernel at the front endof the process, resulting in the production of germ, bran,“high-protein DDGS” and other products (RFA, 2011b). Insome cases, ethanol producers are considering using thecellulosic portions of the maize bran as a feedstock forcellulosic ethanol. The majority of grain ethanol producedaround the world today comes from the dry milling process.In the wet milling process, shelled maize is cleaned toensure it is free from dust and foreign matter. Next, themaize is soaked in water, called “steepwater”, for between20 and 30 hours. As the maize swells and softens, thesteepwater starts to loosen the gluten bonds with themaize, and begins to release the starch. The maize goes on