Biofuel co-products as livestock feed - Opportunities and challenges

494Biofuel co-products as livestock feed – Opportunities and challenges3 500 000FIGURE 12Well-to-wheels total energy use of petroleum fuels and biofuels (J/MJ). Notes: For codes,see Table 5; EtOH = ethanol3 000 000Total Energy Use (J/MJ)2 500 0002 000 0001 500 0001 000 000500 0000DME$PDEMGasoline Diesel Corn-EtOH Switchgrass -EtOHDME$BiodieselDME$HRenewable DieselPump-to-WheelsWell-to-Pump1 400 000FIGURE 13Well-to-wheels fossil energy use of petroleum fuels and biofuels (J/MJ) Notes: For codes,see Table 5; EtOH = ethanolFossil Energy Use (J/MJ) .1 200 0001 000 000800 000600 000400 000200 0000DME$PDEMGasoline Diesel Corn-EtOH Switchgrass -EtOHDME$BiodieselDME$HRenewable DieselPump-to-WheelsWell-to-Pumption and national energy security. More meaningful energydebates should focus on fossil energy or imported energy(such as petroleum energy in the United States context).Figure 14 depicts WTW GHG emissions for each of thepathways analysed. The horizontal axis labels in Figures 12to 14 refer to the code column in Table 5.In Figures 13 and 14, the effect of co-product allocationmethodologies is strongest for biodiesel and renewablediesel. This result stems from the high mass of a non-fuelproduct (soybean meal) that is produced as a by-productof soybean crushing and oil extraction in the pathwaysof these two fuels. In the biodiesel pathway, for example,crushing one litre of soybeans yields 0.14 kg and 0.53 (dry)kg of soy oil and soy meal, respectively. Four times moreanimal feed than oil is therefore produced, strongly affectingmodel outputs as the allocation methodology changes.