Life Cycle Assessment of Yearly Changes in Environmental Impacts of Japanese Dairy Farming

Abstract

The yearly changes in environmental impacts of Japanese dairy farming were evaluated with original sheet data of survey on cost of milk production, conducted by Ministry of Agriculture, Forestry and Fisheries. Global warming, acidification and eutrophication potentials in Hokkaido and the areas except Hokkaido were evaluated by life cycle assessment (LCA). Fourteen year's original sheet data, from 1979 to 1992, were used in this study. The functional unit of LCA was one metric ton of milk produced. The production processes of chemical fertilizers, agrochemicals, materials, machineries and facilities, cultivation of purchased and self-supplied feeds, animal management and manure management were contained within the system boundary of this study. Multiple regression analysis was executed to estimate global warming, acidification and eutrophication potentials with cost of feeds, beddings, electricity and fossil fuels, facilities and machineries, the number of milking cows and the amount of milk produced. And the equations were used to evaluate the environmental impacts from 1993 to 2006. The amount of milk produced per farm was increased within the period from 1979 to 2006. Global warming potentials were decreased after 1982, and became constant after 1997 in Hokkaido and the areas except Hokkaido. The contributions of rumen fermentation and purchased feeds to global warming were high, and the contributions of fossil fuels (Hokkaido) increased from 1979 to 1992. Eutrophication potentials were higher in Hokkaido, but no difference was observed in 1992. From this study, the increase of milking cows per farm, the genetic improvement of milking performance, the quality improvement of feeds, the reduction of methane emission by rumination, the improvement of self-sufficiency of feeds and the greater use of composting methods that have low emission factors were important for reductions of environmental impacts.