Corresponding emission factors for the materials are chosen from the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, as shown in Table 5. Vestas has manufacture factory around Asia, North America, Europe and other places in the world. Therefore, the default emission factor of IPCC is applied in our paper. Energy, mineral industry and metallurgy are three main sources of CO2 emissions, and energy holds the biggest emission intensity. Although emission factors may vary by industrial process, we chose the same default value for different cases in order to compare the environmental impact of different wind power plants.