Biofuel co-products as livestock feed - Opportunities and challenges

6Biofuel co-products as livestock feed – Opportunities and challenges2 440FIGURE 32010 world feedstock usage for biodiesel(thousand tonnes)2 230Rapeseed oilSoybean oilPalm oilSource: F.O. Licht, 2011211 1615 700Animal fats & yellow greaseSunflower oilOther5 750Animal fats and yellow greaseAnimal fats are derived from the rendering process usinganimal tissues as the raw material. The raw material is aby-product of the processing of meat animals and poultry.The amount of fat produced is directly related to the speciesof animal processed and the degree of further processingthat is associated with the marketing and distribution ofthe meat product. Current markets for rendered animal fatsinclude use as feed ingredients for livestock, poultry, companionanimals and aquaculture. In addition, products suchas edible tallow are used for soap and fatty acid production.Industry analysts anticipate that roughly 25 to 30 percentof the rendered animal fat supplies could be diverted tobiodiesel production given current uses (Weber, 2009).In 2010, an estimated 2.2 million tonne of animal fatsand yellow grease was used globally in the production ofbiodiesel (F.O. Licht, 2011), representing 14 percent of thetotal feedstocks used in global biodiesel production. EUproducers used 54 percent of animal fats and yellow greaseprocessed as biodiesel feedstock in 2010, followed by Brazil(16 percent) and the United States (12 percent).Maize oil from ethanol production processesGrain ethanol production may offer the biodiesel industryits nearest-term opportunity for a significant additive supplyof plant oils for biodiesel production. Historically, maizeoil has not been a viable biodiesel feedstock due to itsrelative high cost and high value as edible oil. However, asdiscussed earlier, some dry-mill ethanol plants in the UnitedStates are now removing crude maize oil from the stillageat the back end of the process. The maize oil is typicallymarketed as an individual feed ingredient or sold as a feedstockfor further processing (e.g. for biodiesel production).Maize oil could help to meet feedstock market demand intwo ways. First, edible maize oil could displace other edibleoils that could then be diverted to biodiesel production.Second, non-edible maize oil could be used directly forbiodiesel production.Biodiesel production processRegardless of the feedstock, most biodiesel globally is producedusing one of three common manufacturing methods:reaction of the triglycerides with an alcohol, using abase catalyst; reaction of the triglycerides with an alcohol,using a strong acid catalyst; or conversion of the triglyceridesto fatty acids, and a subsequent reaction of the fattyacids with an alcohol using a strong acid catalyst.In the United States and elsewhere, biodiesel is commonlyproduced using the base-catalyzed reaction of thetriglycerides with alcohol. Methanol is currently the mainalcohol used commercially for the production of biodieseldue to its cost relative to other alcohols, shorter reactiontimes compared with other alcohols, and the difficulty andcost of recycling other alcohols.Use of acid catalysis is typically limited to the conversionof the fatty acid fraction in high free fatty acid feedstocks,or to treat intermediate high fatty acid/ester streams thatcan form in the acidification of the crude glycerin bottomsproduced as a co-product of the transesterification reaction.Stoichiometrically, 100 kg of triglycerides are reactedwith 10 kg of alcohol in the presence of a base catalystto produce 10 kg of glycerin and 100 kg of mono-alkylesters or biodiesel. In practice, an excess amount of alcoholis used in the reaction to assist in quick and completeconversion of the triglycerides to the esters, and the excessalcohol is later recovered for re-use. All reactants must beessentially free from water. The catalyst is usually sodiummethoxide, sodium hydroxide or potassium hydroxide thathas already been mixed with the alcohol.In some cases, the free fatty acid levels of the feedstockutilized are elevated to the point that an esterificationstep, using an acid catalyst, is incorporated into thebiodiesel processing sequence. This stage involves mixingthe high fatty acid material with a solution of methanolthat contains an acid catalyst, typically sulphuric acid. Thecontained fatty acids are then converted to methyl ester.An excess of methanol and H 2 SO 4 is employed to ensureconversion, and after reaction completion this excess isseparated from the ester phase. The conversion of the fattyacid to ester results in the formation of water, thus afterthe reaction there is water in the methanol+sulphuric acidmixture. Since this is an equilibrium reaction, the presence