تاثیرات زیست محیطی تولید شیر در سراسر گرادیان تشدید در اتیوپی

This paper quantifies environmental performances of milk production systems differing in degree of intensification in the Mekelle milkshed area, Ethiopia. Life Cycle Assessment (LCA) methodology was used to estimate Land Use (LU), Fossil Energy Use (FEU) and Global Warming Potential (GWP) of the cattle sub-system in 8 large-scale, 8 (peri-)urban and 8 rural farms. The large-scale farms owned considerably more and other types of cattle (35.0 cattle units (cu); mainly Friesians) than the (peri-)urban (6.3 cu; mainly crossbreds) and rural farms (4.1 cu; mainly local breeds). The milk production per average cow per year was much lower in rural farms (730 kg) than in large-scale (2377 kg) and (peri-)urban farms (1829 kg). Milk was the main contributor to the economic benefits of the large-scale (90%) and (peri-)urban (80%) farms, whereas milk (sold and consumed at home) contributed only about 40% to the economic benefits in the multifunctional rural farms. The environmental impacts per cu, reflecting the absolute impacts of cattle keeping, were considerably higher in the large-scale and (peri-)urban farms than in the rural farms. LU and FEU were for the great majority caused by the land use for hay, straws and grasses, and harvesting, transport and processing of feeds, in particular wheat bran. On-farm emissions from enteric fermentation and manure storage were the main contributors to GWP. The impacts per kg milk did not differ significantly between the three systems. The LU per kg milk estimates (9.4, 11.2 and 8.8 m2 in the large-scale, (peri-)urban and rural farms, respectively) were relatively high compared to LCA studies of milk production in developed countries due to large amounts of low-quality forages and wheat bran fed, whereas the FEU values per kg milk (7.5, 11.1 and 6.6 MJ in the large-scale, (peri-)urban and rural farms, respectively) were relatively low compared to studies of milk production systems in developed countries. The GWP estimates per kg milk (1.75, 2.25 and 2.22 kg CO2-equivalents per kg milk in the large-scale, (peri-)urban and rural farms, respectively) were slightly higher than GWP values for the same types of farms in other developing countries, due to the relatively large amounts of low quality feeds fed. The quality of cattle management practices seems more important than the choice for a specific cattle keeping system in reducing environmental impacts of milk production.