Nickel pig iron is composed of low-grade nickel ore, coking coal, and a mixture of gravel and sand as an aggregate. This mixture is heated in either a blast furnace or an electric arc furnace depending on the desired grade. Impurities are then removed via smelting and sintering processes and the resulting nickel pig iron contains four to 13 percent pure nickel. According to Canadian Sudbury nickel pig iron equals "dirty nickel", because the production process is not environmentally friendly, the carbon dioxide emissions being particularly high. China has imported most of the nickel containing ore fromIndonesia and the Philippines, but Indonesia has imposed a 20 percent tax on nickel ore exports and this tax is forecasted to rise before a complete export ban in 2014. China imported 53 percent of the nickel ore from Indonesia in 2011.