Biofuel co-products as livestock feed - Opportunities and challenges

An outlook on EU biofuel production and its implications for the animal feed industry 17FIGURE 4Feed conversion efficiency for different biofuel processes (MJ usable product energy per MJ lower heatingvalue of feed)BIOFUEL ENERGY PRODUCTION EFFICIENCY FROM CROP (MJ/MJ)0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Fermentation/Starch &sugar cropsTransesterification/OilseedsAnaerobic digestion/Green maizeFermentation/CornstoverFischer Tropsch Biomass toLiquids/Woodefficiency of food crops for biofuel, due to the heat of reactionin the biofuel conversion process. The non-extracted oiland fermentation by-products are all conserved to providemetabolizable energy in the animal feed co-products, whileall the other plant components, such as protein and minerals,become concentrated and conserved in the animalfeed. Processes that are used for non-food feeds have alower feed efficiency, with a large proportion of the feedstockenergy lost as unprocessed feed, by-product losses,or heat release during reaction stages. Any protein in thefeedstock is decomposed and lost.The overall feed conversion efficiencies of producingalternative biofuels by the different processes are shownin Figure 4. Low feed efficiencies are often associated withlower inputs of fossil energy to the conversion process,or potential export energy. These vary depending on thedetailed process design and will determine the plant’s GHGemissions, but are not included in Figure 4.This demonstrates that due to the low energy efficiencyof anaerobic digestion and gasification processes, theyshould only be used for feedstocks that are not suitablefor starch, sugar or vegetable oil extraction. The averageharvested yields of lignocellulosic crops in the EU, such asmiscanthus and short rotation coppice, are about 11 dry t/ha and are similar to the yields of food crops, such as cereals(including straw and stover). However, there are largeyield variations due to weather, land quality and crop management,and substantially higher than average yields canbe obtained both for lignocellulosic crops and food crops.Thus, despite comparable yields of lignocellulosic and foodUseful energy yield GJ/ha/yrFIGURE 5Useful crop energy and protein yields for cropsin NW Europe12010080604020SunflowerMaizeFeed WheatBarleyRapeseedRyeField beansPeasSoy bean00.0 0.2 0.4 0.6 0.8 1.0 1.2Sources: FAOSTAT, 2011; Premier, 2008.Protein yield t/hacrops, the low energy efficiency of processes using lignocellulosicfeedstocks results in there being no carbon benefitcompared with processing food crops.BIOFUEL CROPSFood crops produce several commercially useful plantproducts, primarily protein, carbohydrate and lipid (oil orfat) and minerals. It is convenient for understanding theimplications of biofuels for the animal feed industry tofocus on the protein and energy levels and yields in differentcrops. The protein and energy yields for a range ofmedium- and high-protein crops grown in NW Europe areshown in Figure 5.