Biofuel co-products as livestock feed - Opportunities and challenges

18Biofuel co-products as livestock feed – Opportunities and challengesFIGURE 6Useful crop energy versus protein content for cropsin NW EuropeUseful Energy Yield GJ/ha/yr250200150Sugar BeetMaize10050Feed WheatBarleyRyeRapeseedSunflowerField beansPeasSoy bean00 5 10 15 20 25 30 35 40 45Protein content g/ 100g dry massSources: FAOSTAT, 2011; Premier, 2008.The useful crop energy is the average metabolizableenergy (for ruminants, pigs and poultry) of the crop, or foroil seeds it is the metabolizable energy of the meal (Premier,2008) plus the lower heating value of the extracted vegetableoil. The crop yields for NW Europe are the averagefor United Kingdom, Ireland, France, Germany, Denmark,Belgium and the Netherlands for the period 2005 to 2009(FAOSTAT, 2011). Figure 5 shows that the protein yieldsof many crops, including wheat, beans and soybean arefairly similar, with yields around 0.8 to 1.0 t/ha. Althoughsoybeans and field beans are recognized as being proteincrops, due to their high protein content, the protein yieldis little higher than for wheat and maize. However, theenergy yields of cereal crops such as wheat and maize aresubstantially higher than protein crops such as soybean andfield beans.An important advantage of oil seeds and legumes is thatthey have a higher protein concentration, compared withcereals, which is important for animal feed compounding.The energy yields of biofuel crops grown in NW Europeand the metabolizable energy of associated co-products arecompared in Figure 7.There is a clear relationship: the higher the concentrationof protein per unit dry mass of recovered crop, thelower the useful energy yield of the crop. Crops with highprotein content are grown to provide high-protein animalfeeds, despite their similar protein and lower energy yields.The energy yields of biofuel crops grown in NW Europeare compared in Figure 7.It is assumed from the data in Figure 4 that all the energyin oilseed crops is conserved when they are used for biofuelproduction. Figure 7 demonstrates that nearly all the energyin cereal crops is also conserved when they are used for biofuelproduction. While both the biofuel energy and metabolizableenergy yields are higher for cereal crops than oilseedcrops, cereal crops need a break crop, typically oilseed rape,every three or four years as part of the crop rotation.Biofuel crop capacity and growth ratesThe proportion of EU crops used to produce EU biofuelsfrom cereals, oilseeds and sugar beet in 2009 is shown inFIGURE 7Metabolizable and biofuel energy yields of selected biofuel crops in NW Europe120100Crop energy yield GJ/ha/yr806040200FeedwheatMaizeWheatbiofuelMaizebiofuelRape Sunflower SoyBiofuel energyMetabolizable energySources: FAOSTAT, 2011; Premier, 2008.