The most common metals to consider when discussing recycling are aluminum and steel. Some other metals–like gold, silver, brass, and copper–are so valuable that they are rarely thrown away. They do not create a waste disposal problem.
Aluminum and steel do. Americans use 100 million steel cans and 200 million aluminum beverage cans every day. What should we do with this metal waste? Should we burn it in waste-to-energy plant? Should we landfill it? Or should we recycle it?
After source reduction (using less aluminum to make a can, for example), recycling is the most efficient way to reduce aluminum and steel waste.
Unlike paper and plastics,burning metal trash in waste-to-energy plants creates no energy. Instead, aluminum melts and steel just gets very hot. Magnets can be used to collect steel scrap at waste-to-energy plants, though, and then the scrap can be shipped to steel plants for recycling.
Landfilling is usually not a good alternative either. Aluminum, in particular, is so valuable as a scrap material that it simply does not make sense to bury it.
Recycling Aluminum
ALUMINUM cycle
1. You enjoy your favorite beverage in an aluminum can
2. You are a good "sort." You put the aluminum can in a bag for recycling.
3. Recycling company takes the cans to a recycling plant. The aluminum is shredded and melted.
4. The molten aluminum is gradually hardened into ingot form.
5. Ingots are made into aluminum sheets or other desired forms.
6. The aluminum is made into new cans, and the cycle begins again.
Like most metals, aluminum is an ore. An ore is a mineral that is mined for a valuable material contained within it. Bauxite, a reddish clay-like ore, is rich in aluminum compounds.
The tricky thing about aluminum—unlike copper, iron, and other common metals—is that it only exists in combination with other elements, usually oxygen. Combined with oxygen, aluminum forms an extremely hard material known as alumina. To free the aluminum, the alumina must be stripped or reduced of its oxygen. This process is done at a reduction plant, or smelter. The alumina is put into large pots at the reduction plant. First, it is dissolved in a molten (or liquid) salt.
Then, a powerful electric current is run through the liquid to separate the aluminum from the oxygen. The molten aluminum sinks to the bottom of the pots. The reduction process requires a tremendous amount of electrical energy.
That is why recycling aluminum makes sense. It saves energy—a lot of energy. Today, aluminum can recycling saves about 11.5 billion kilowatt-hours (kWh)—enough electricity to light a city the size of Pittsburgh for six years.
As you probably know, energy is expensive! Just take a look at your electric bill, or note the price of a gallon of gasoline the next time you see a gas station. Making a pound of aluminum from bauxite ore (a pound is about how much 34 aluminum beverage cans weigh) takes 7.5 kilowatt-hours of electricity.
Making aluminum from recycled aluminum scrap, on the other hand, takes only four percent of the energy—just one-third kWh. Recycling four aluminum cans saves as much energy as the energy in one cup of gasoline.
That is also why used aluminum items have a high scrap value. Aluminum manufacturers save energy and money by using recycled aluminum, so they will pay you for your old cans—about a penny for every can. One could sell scrap aluminum, or any metal for that fact, to a scrap yard aka a salvage yard. [1]
Steel Recycling
Steel is the most recycled material in the United States. Steel dominates the recycling mix because every year the steel industry recycles huge amounts of steel scrap from cars, appliances, and torn-down buildings and bridges. Today, all steel products are made with some recycled steel.
SAVING energy by recycling STEEL The average family in the United States uses 90 pounds of steel cans a year.
- Recycling that steel would save: 144 KWh of electricity
- 63 lbs of coal
- 112 lbs of iron
- 5.4 lbs of limestone
In 1998, the amount of steel that was recycled decreased for the first time in many years. Foreign countries were selling their steel so cheaply that the recycling industry suffered a decline. Today, it is increasing again.
You can do your part at home by recycling steel cans. A steel can is the can your soup comes in, or your dog’s food, or your mom’s coffee, or the whip cream you squirt on top of an ice-cream sundae. In fact, most food containers are made of steel.
You have probably heard many people call a steel can a tin can. Steel cans are often called tin cans because they are usually coated with a thin layer of tin. Tin protects the food that is cooked in the can.
THE ABCs OF STEEL
Steel and aluminum are both mined from ores, and are made in a similar way. The essential ingredient in steel making is iron ore. Iron ore is plentiful, but we cannot use it as it occurs in nature. Iron is usually combined with oxygen, or with other elements, like carbon and sulfur. We must smelt the iron ore—strip or reduce it of its oxygen—to get to the iron.
It takes a great deal of energy to reduce iron oxides. An oxide is a compound with oxygen and some other element. The reduction takes place in a very hot blast furnace. A chemical reaction takes place in the blast furnace, and the iron is freed from the oxygen. This free iron (called pig iron by steel makers because it forms a pattern that looks like tiny piglets surrounding their mother) is used to make steel.
Steel recycling saves a lot of energy. It is much more energy efficient to use steel scrap to make new steel than to mine the iron ore and then smelt it in a blast furnace. It takes about 60 percent less energy to make steel from recycled materials than it does from iron ore. That’s why today’s steel makers always use some steel scrap to make new steel products.
Steel is probably the easiest material to separate from the rest of the solid waste stream. Steel is attracted to magnets, so special magnetic belts can be used to separate steel cans from other recyclables. This is a much more efficient method than the labor-intensive hand-sorting necessary with other recyclables, such as plastics.
Recycling your used steel cans at home is easy, too. All you need to do is rinse the food from the cans. That’s it. Years ago, scrap dealers asked people to remove the paper labels and the tops and bottoms from cans. This is no longer necessary.
If you’re not sure which cans are steel and which are aluminum, use a magnet to separate them. Steel will stick to the magnet; aluminum will not. If you come across a can with a steel body and an aluminum top—called a bimetal can—put the can with the steel recyclables. Steel recyclers can accept all types of steel cans, even those containing aluminum. Aluminum recyclers can only accept 100 percent aluminum cans.
After steel scrap is collected from homes, recycling centers, or waste-to-energy plants, it is shipped to one of the companies that buy old steel—steel mills, iron and steel foundries, scrap dealers, and detinners. Detinners remove the layer of tin from old steel cans. This tin is valuable and can be sold.
Steel can recycling follows almost the same process as aluminum can recycling. Steel cans, along with other steel scrap, are melted in a furnace and then poured into casters that continuously roll and flatten the steel into sheets. Recycled steel cans can be made into new cars, girders for buildings, or new food cans. In the U.S., steel cans and other steel products contain at least 25 percent recycled steel, with some containing nearly 100 percent recycled steel.
Like aluminum, steel can also be recycled again and again. It does not lose any of its strength or quality in the recycling process. It can be a never-ending process that continues to save energy and resources.
References
- ↑ A Guide for Scrap Metal Beginners. Retrieved on 2010-11-12.