Biofuel co-products as livestock feed - Opportunities and challenges

36Biofuel co-products as livestock feed – Opportunities and challengesMAIN MESSAGES• Although 140 biodiesel plants produced 1.2 billionlitres of biodiesel in 2010, very little crudeglycerin has been used in animal feeds in theUnited States due to relatively low volumeproduced compared with ethanol industry coproducts,and competition with higher valueconsumer product and industrial uses.• DG serves primarily as an energy source in animalfeeds, but also contributes a significant amountof protein and amino acids, and is high in digestiblephosphorus compared with other grains andgrain by-products used in animal feeds.• Dietary inclusion rates have been increasing inrecent years because of the increasing price ofmaize and the high energy value DDGS providesto animal feeds at a lower cost.• Relative value of DG varies by animal species,the price differential between maize and soybeanmeal, and geographical region.• DG has become the most popular alternativeingredient used in beef, dairy, swine and poultrydiets in the United States and in over 50 countriesworldwide because of abundant supply,excellent feeding value and low cost relative tomaize and soybean meal.• The most significant barrier for domestic andinternational feed industry acceptance has beenthe variability of nutrient content and digestibilityamong DG sources.• As ethanol production technology continues toevolve, so does the composition and diversity ofco-products resulting from these processes.• Use of alternative feedstocks, such as othergrains, sources of cellulose, and algae, alongwith the possibility of phytate phosphorusextraction and other technologies, will dramaticallychange the availability and nutritional compositionof co-products.• Emerging new markets for DG include aquaculture,horses and companion animal feeds, andhuman foods, but further research to supportthese market applications is needed.INTRODUCTIONAs a result of the exponential growth of the United Statesethanol industry during the past decade, distillers grain(DG) co-products from dry-grind ethanol production havebeen produced in great quantities, and have affected thefeed industry to a much greater extent than other biofuelco-products combined. Lesser amounts of maize co-products(maize gluten feed, maize gluten meal and maize germmeal) are produced by the wet-milling segment of the fuelethanol industry, but have also been extensively used in theUnited States feed industry for more than 30 years.Biodiesel is produced using a variety of esterificationtechnologies. New or used vegetable oils and animal fatsare used as the initial feedstock. These feedstocks arefiltered and pre-processed to remove water and contaminants,followed by mixing with an alcohol (usually methanol)and a catalyst (sodium or potassium methylate). Thiscauses the oil molecules (triglycerides) to be broken apartinto methylesters and glycerin, which are then separatedfrom each other and purified (Figure 1).Biodiesel production in the United States rapidly expandedfrom 2005 (424 million litres) to 2008 (2.6 billion litres),but declined from 2009 (2.1 billion litres) to 2010, with1.2 billion litres being produced from 140 plants withinthe United States (Figure 2). The principal co-product ofthe biodiesel production is crude glycerin (Ma and Hanna,1999; van Gerpen, 2005), with 0.08 kg of crude glycerinMethanol + KOHMethanolrecoveryFIGURE 1General biodiesel production processVegetable oilsBASIC TECHNOLOGYTransesterificationCrude glycerinGlycerinrefiningGlycerinRecycled greasesDilute AcidEsterificationCrude biodieselRefiningBiodieselSulphuric acid+ methanolgenerated for every litre of biodiesel produced. As a resultof the recent decline in biodiesel production and consequentreduced availability of crude glycerin, along withcompeting uses in consumer and industrial products, verylittle crude glycerin has been used in the United States feedindustry. Examples of non-feed uses of glycerin include:• moistening, sweetening and preserving foods and drinks(soft drinks, candies, cakes, casings for meats andcheese, dry pet foods, etc.);