Biofuel co-products as livestock feed - Opportunities and challenges

48Biofuel co-products as livestock feed – Opportunities and challengesnutrient content and digestibility, but not maximum dietaryinclusion rates or their effects on animal performance.Until significant quantities of new maize co-products areproduced commercially—and more research conducted—itis difficult to determine their comparative feeding value forvarious animal species.OTHER EMERGING OR POTENTIAL PROCESSINGAND MAIZE CO-PRODUCT PRODUCTIONTECHNOLOGIESPhosphorus extractionThe phosphorus content of maize is concentrated threetimes during the ethanol and DDGS production process,and also becomes more bio-available (50 to 60 percent)in DDGS for non-ruminant animals compared with maize(approximately 15 percent), because a portion of phytateP is converted to inorganic P (Noureddini et al., 2009).This makes DDGS an excellent phosphorus source foranimal feed. However, the total phosphorus in DDGS issignificantly higher than maize and 40 to 50 percent of itremains stored in phytate-mineral complexes. At currentdietary DDGS inclusion rates, animal are consuming morephosphorus than they require. Under normal physiologicalconditions, the dietary phytate phosphorus that cannot beutilized by the animal will pass through the gastro intestinaltract and eventually result in high phosphorus content inmanure that could pollute surface waters and create environmentalconcerns.Phytic acid and phytate are valuable chemicals thatare widely used in many commercial applications in thefood, industrial and medical fields. Currently, there areno major phytic acid manufacturers in the United Statesand all of the phytic acid and its salts sold domesticallyare either imported or toll-manufactured. The majorcommercial production companies are primarily located inJapan and China. Phytic acid can be produced from manytypes of feed commodities, such as bran from maize, riceand wheat, and from cottonseed meal. However, maizeco-products can be a practical source for manufacturingphytic acid in the United States, considering the volumeof co-products currently being produced. The extractionis a relatively simple and mature process, and easyto implement commercially. Furthermore, after phytateextraction, the residual material can still be used as avaluable feed ingredient in animal feeds. Applying thisprocess to DDGS would create extra profits and jobopportunities for ethanol plants by selling a commerciallyvaluable product currently imported. Phytate extraction hasmany positive benefits, including removal of undigestiblephytate phosphorus from DDGS, decreasing phosphorusexcretion in manure, and increasing nutritional value ofDDGS by improving the digestibility of other nutrientspreviously immobilized by phytate.Fibre extractionSeveral methods have been developed to extract the fibrefrom maize before fermentation, or extract fibre fromthe DG after fermentation, which have created substantialopportunities to add value to the ethanol and maizeco-product production process (Brekke, no date). Maizegrain contains about 2 percent fibre, and can be moreconveniently and economically utilized as a feedstock forfurther ethanol production (with the appropriate technology)compared with most other sources of fibre becausealternatives imply substantial cost for material handlingand transport. Once fibre is removed by fractionation, ithas two potentially valuable uses in an ethanol plant: it canserve as fuel source in a biomass boiler for operating theplant; or, if cellulosic ethanol production technologies areadded to an existing maize ethanol plant, fibre can serveas an additional feedstock for ethanol production. In eithercase, the DG resulting from a process that removes some,or most, of the fibre (and only the fibre) would be expectedto be higher in protein, fat and other nutrients than DG coproductsproduced using the entire maize kernel.Maize fibre also has potential food and feed uses outsideof the ethanol plant. For example, maize fibre can beused as a fibre supplement in human nutrition. For animalfeeds, POET, one of the major ethanol producers in theUnited States, is producing and marketing a product calledDakota Bran that includes maize bran as one of its principlecomponents (DakotaGold, 2007).Drying systemsNutritional quality and digestibility of DDGS is highlydependent on the drying process used in ethanol productionfacilities. In general, the dry-grind ethanol industryutilizes rotary drum driers that are fueled with natural gas.Internal temperatures range from 500 o F [250 °C] to asmuch as 1100 o F [600 °C]. As ethanol fermentation efficiencyimproves, drier system capacity can be exceeded,resulting in shorter drying times and the use of highertemperatures to increase throughput, which can negativelyaffect the nutritional value of DDGS. High temperaturesand prolonged drying time can result in damage to aminoacids and destruction of some other nutrients. As a result,some ethanol plants use multiple rotary drum driers in theirsystems to reduce heat damage to DDGS.Use of microwaves is a relatively new drying technology,and is only being used by a few ethanol plants in the industry.Microwaves are radio waves that cause water moleculesto vibrate very fast, and the friction between the vibratingwater molecules produces the heat that allows drying.According to literature from Cellencor, one of the companiesproviding microwave systems to the ethanol industryin the United States, the temperature of the DDGS doesnot exceed 200 o F [93 °C] in the drying process, “so the