Reducing energy inputs to a simulated dairy farm

Abstract

Mixed-integer linear programming was used to simulate the energy requirements of a 50-ha and 50 cow dairy farm. The farm could be configured for 24 combinations of: diesel fuel or on-farm ethanol fuel production; surface applied or injected manure management alternatives; continuous corn, corn-soybeans or corn-alfalfa crop sequences; or conventional tillage or no-tillage corn production. The model analyzed the flow of total energy (the sum of direct and indirect) produced and/or consumed inside the farm boundaries and the energy crossing the farm boundaries as inputs or outputs. Substituting on-farm produced fuel ethanol for diesel fuel reduced the external fossil energy inputs to the farm for all configurations by 15–19%. In contrast, the total energy consumption of these configurations was 12–38% greater than the diesel-based configurations. Manure injection and surface application alternatives affected total energy utilization by <10% for all farm configurations. Energy inputs in fertilizer nitrogen were 62 and 79% less for soybean and alfalfa-based crop sequences, respectively, than the continuous-corn sequence. No-till corn production generally had less effect on external energy inputs than the selection of manure management alternatives. External energy per product ratio ranged from 3.88 GJ Mg −1 milk for diesel fuel/conventional tillage/surface manure application to 1.78 GJ Mg −1 milk for on-farm fuel/conventional tillage/injected manure application. Total energy per product ratio ranged from 4.38 GJ Mg −1 milk for on-farm fuel/conventional tillage/surface manure application to 2.08 GJ Mg −1 milk for diesel fuel/no-till/injected manure application. Since external energy input and total energy consumption are not always directly linked, the energy use goals for a farm must be clearly specified and the implications understood when farm management selections are made. Otherwise, the intended energy use goals may not be reached.