does not require a large energy output of a melting process. In 2003, half of the products manufactured with aluminium were sourced from recycled aluminium material. Environmental savings The benefit with respect to emissions of carbon dioxide depends in part on the type of energy used. Electrolysis can be done using electricity from non-fossil-fuel sources, such as nuclear, geothermal, hydroelectric, or solar. Aluminium production is attracted to sources of cheap electricity. Canada, Brazil, Norway, and Venezuela have 61 to 99% hydroelectric power and are major aluminium producers. However the anodes widely used in the Hall–Héroult process are made of carbon and are consumed during aluminum production, generating large quantities of carbon dioxide, regardless of electricity source. Efforts are underway to eliminate the need for carbon anodes. The use of recycled aluminium also decreases the need for mining and refining bauxite. The vast amount of aluminium used means that even small percentage losses are large expenses, so the flow of material is well monitored and accounted for financial reasons. Efficient production and recycling benefits the environment as well. Process for beverage cans Aluminium beverage cans are usually recycled by the following method: Cans are first divided from municipal waste, usually through an eddy current separator, and cut into small, equally sized pieces to lessen the volume and make it easier for the machines that separate them. Pieces are cleaned chemically/mechanically and blocked to minimize oxidation losses when melted. (The surface of aluminium readily oxidizes back into aluminium oxide when exposed to oxygen.) Blocks are loaded into the furnace and heated to 750 °C ± 100 °C to produce molten aluminium. Dross is removed, and the dissolved hydrogen is degassed. (Molten aluminium readily disassociates hydrogen from water vapor and hydrocarbon contaminants.) This is typically done with chlorine and nitrogen gas. Hexachloroethane tablets are normally used as the source for chlorine. Ammonium perchlorate can also be used, as it decomposes mainly into chlorine, nitrogen, and oxygen when heated. Samples are taken for spectroscopic analysis. Depending on the final product desired, high-purity aluminium, copper, zinc, manganese, silicon, and/or magnesium is added to alter the molten composition to the proper alloy specification. The top-five aluminium alloys produced are 6061, 7075, 1100, 6063, and 2024. The furnace is tapped, the molten aluminium poured out, and the process is repeated again for the next batch. Depending on the end product, it may be cast into ingots, billets,