Comparative energy, economic and environmental analyses of forage production systems for dairy farming

Corn silage and alfalfa hay are the main feedstuffs for dairy farming, and due to the drop in corn price, there is a tendency toward replacing alfalfa hay with corn silage in dairy cow diets. This study focuses on the comprehensive assessment of alfalfa hay and corn silage production systems from energy, economic and environmental perspectives. The life cycle assessment (LCA) from raw material extraction up to delivery of forage to the dairy farms was conducted to quantify the ecoprofile of forage production. The results of comparative analyses revealed that corn production was more dependent on chemical fertilizers specially nitrogen, but alfalfa production was more dependent on electricity, water and diesel fuel for farm operations. Energy use per ton of alfalfa hay dry matter was higher than that of corn silage (2.6 vs. 2.4 GJ t−1). On the other hand, output energy of alfalfa hay was considerably higher than that of corn silage (15.8 vs. 8.0 GJ t−1). Consequently, energy use efficiency of alfalfa hay was almost two times of that of corn silage (6.1 vs. 3.3). Nevertheless, corn silage had higher benefit-to-cost ratio than alfalfa hay (2.55 vs. 2.27), and higher environmental impacts in the forms of abiotic depletion, global warming potential, marine aquatic ecotoxicity, photochemical oxidation, acidification and eutrophication potential. Finally, the effects of varying input parameters of machinery and diesel fuel, electricity, seeds, fertilizers, pesticides and transportation on LCA results were assessed via sensitivity analysis.