The next step consists of pouring molten aluminum into molds and letting the aluminum solidify into shape. These blocks of solid aluminum, or ingots, are forced through several rollers to become sheets that are less than 1-inch thick. The aluminum sheets are cut to make cans, which are sent to soft drink companies that fill and seal them. The canned soft drinks are sold to consumers who drink them.
In the Western world, the cans are usually collected and sent to a recycling center, where they are cleaned, sorted, and crushed. Then, they go to an aluminum manufacturing plant, where they are shredded, remelted and solidified again.
In India, the cans are collected from garbage dumps and sent to small private companies, where people such as Hamed clean them using acid at room temperature and normal pressure. Then, they melt the aluminum cans in a furnace at 660 oC and pour the molten aluminum into a mold, which later solidify into shape.
Recycling aluminum is much cheaper than extracting it. Aluminum extraction requires temperatures of 1,000 oC and a lot of energy. Additional material—such as cryolite and sodium hydroxide—need to be used, and a significant amount of electricity is needed.
Advantages of recycling aluminum
The key benefit of recycling is that it reduces the amount of waste that needs to be buried or burned. In the case of aluminum, there is also another advantage. If old soda cans were simply buried, new cans would have to be made from new aluminum that would have to come from aluminum ore. So, recycling aluminum has an economic advantage as well as an environmental one.
Not all materials are economically advantageous to recycle. Plastic, for example, is often cheaper to produce from raw materials than it is to recycle. So, while plastic is endlessly recyclable, it is often burned or simply buried because it is not cost-effective to recycle it.
Other constraints also make materials, such as green glass, less desirable to recycle. It is not that the glass cannot be endlessly recycled, it is because the color of glass cannot be changed—once it is green, it will be green forever. A lot of green glass is imported into the United States, containing foreign-made beverages such as wine and beer. But few products are manufactured from green glass in the United States, meaning that most of it is not recycled.
Another reason aluminum is easier to recycle is because it does not corrode, unlike other metals such as iron. If left unprotected, iron is transformed by the corrosive process of rusting into iron oxide. When that happens, the metal has to undergo expensive treatment to remove the oxygen while aluminum, which does not corrode, can simply be melted and molded into a new product.
Thanks to Dharavi residents such as Hamed, a high proportion of aluminum is recycled in India. If it were not for their efforts, nothing would be recycled at all. A big difference between India and the United States is that in India, there is no government recycling program. Indians do not have to separate their waste, while U.S. residents are encouraged to do so.
Hundreds of thousands of Indians forage for recyclable materials in public trash cans. Doing this work exposes them to several health risks because they are working in an unclean environment. Recycling plant workers such as Hamed also face health risks. They are not provided with any safety equipment, even though they work near a furnace that has a temperature of 660 oC. Hamed, for example, works 11 hours per day, enjoys very little time off, and has no chance of attending school. Although Hamed and others are working in the most appalling conditions, the alternative is having no way to make a living.
In the United States, recycling feels like a good habit that some of us try to adopt. In India, it is a lifeline for people struggling to survive. There, aluminum recycling has helped transform local economies, which serves to remind us that recycling not only can improve the environment but can change lives as well.