This article addresses the issue of whether or not metal tin cans can be an environmental problem. Metal packaging is common in the household and it is therefore interesting to expand their knowledge in this area.
Cans can consist of steel or aluminum. A can of steel can is usually coated with a thin tin layer. More than 40 billion canning jars are manufactured in the world every year. They can be the packaging that provides the longest shelf life for its food.
Examples of metal packaging:
- cans
- caviar Tubes
- Aluminum foil
- Molds
- Metal caps
- closures
- Tubes from drugs
- Paint cans, dry and brush clean
- spray cans
- beverage cans
- Barrels, eg oil barrels
- commodities
Metal packaging consists of steel sheet or aluminum. Steel is an alloy of iron with less than 2% carbon. The steel sheet can be tinned and is then called tinplate – about 0.3% of the can’s mass is then tin. The aluminum in aluminum can tins is alloyed with 0.5% manganese and 0.5% magnesium to make the material stronger.
Iron
Iron has the chemical formula Fe from the Latin name ferrum. The melting point is 1539 ° C. Iron has been man’s most important metal since 3000 years. It is the fourth most common substance and the cheapest metal. It is found in iron ore mainly as oxides, for example as magnetite (Fe3O4) in black ore and as hematite (Fe3O3) in bloodstone ore, but also as sulfides and carbonate. Iron ore is mined all over the world. Iron is affected by magnets. Iron is part of the hemoglobin which is used to transport oxygen in the body.
Tin
Tin has the chemical formula Sn from the Latin name stannum. The melting point is 232 ° C. It has been used by man since prehistoric times. Tin is a deficiency metal and occurs mainly in the mineral cassiterite (tartar). Tin does not rust and withstand other corrosion. Organic tin compounds are toxic, they were used for example in boat bottom colors but have now been banned.
Aluminum
Aluminum has the chemical formula A1. The melting point is 660 ° C. It was discovered in 1827. It is the third most common substance and accounts for over 8% of the earth’s crust and 7% of ordinary surface soil in some countries. It is mainly extracted from the bauxite rock by electrolytic pathway. Bauxite is found in tropical areas. Aluminum quickly gains an oxide coating that protects against continued corrosion. Aluminum can be affected by eddy currents. The eddy current effect in aluminum is used in electricity meters. Aluminum is suspected to play a role in the onset of neurological disorders, but the relationship is probably weak.
Extraction and manufacturing
Mining waste is the largest source of metal emissions in nature. The slag contains toxic heavy metals. The acid rainfall makes this a growing problem. Attempts are being made to cover the leaching, among other things.
Extraction is also energy intensive. This is especially true for aluminum – it takes up to twenty times more energy to produce 1 tonne of aluminum from bauxite than it does to re-melt 1 tonne of aluminum packaging.
Emissions of heavy metals and flue gases from the melters occur.
Shipments
Postcar Cans can weigh more than, for example, aluminum-laminated cardboard, in addition, the cans are bulkier than cardboard when transported to the filler. The carton is delivered on a roll. This means that the transport of canning jars consumes more fuel than the transport of cardboard material.
The reason for using a thin (6 µm) aluminum layer in the carton is that it acts as an effective barrier against substances that could penetrate and exit the package.
Waste
If you throw away the metal packaging in the regular garbage, they will be deposited or incinerated. Deposition causes the metal to disappear from the cycle. At certain landfills, the waste goes to landfill in biocell. The biocell is a compartment in the tip where waste is broken down by microorganisms into methane gas, which is used for electricity and heat production at a local cogeneration plant.
A certain amount of household waste goes to digestion where gas for vehicle operation is extracted and you also get fertilizer which is used instead of artificial fertilizer. A small amount of steel canning can have a positive effect on the decomposition. If it can then be formed organic tin compounds I do not know.
Fire If you burn the household garbage, aluminum can be oxidized and then develop 30 MJ / kg, this applies mainly to aluminum in aluminum-laminated cardboard. Energy development is roughly the same as for coal. In combustion, carbon dioxide is not formed but only harmless alumina.
Steel canning jars in the garbage can reduce the energy exchange during combustion. During combustion, organic tin compounds are formed, which are bonded to the dust. Hose filters or water filters are used to separate the dust from the flue gases. The toxic dust is then deposited under controlled forms.
Despite the combustion, iron scrap can still be extracted from the ashes with strong magnets, but the iron exchange becomes worse because the combustion causes some of the iron to be oxidized. Due to new EU regulations regarding the purity of metals, it has become more difficult for steel mills to accept iron scrap from waste incineration.
Collected packaging
The packages should be handed in cleaned and compressed. It is especially important to clean aluminum as the food residues catch fire in the melt and oxidize aluminum which cannot then be reused. Unfortunately, it is often the most difficult to clean aluminum packages as they are often small and sticky or have been used in the oven with burnt food residues on the edges. If you use a lot of hot water for cleaning, the overall energy economy becomes more questionable. However, it is better to hand in unclean packages than not to hand them in at all. However, the steamer (see below) reduces the problem of food residues during melting than would otherwise be the case.
The cleaning provides an odor- and bacteria-free environment for those who handle the packaging. Rats are also avoided at the recycling stations. It is said that the cork should be screwed onto the tubes as they cannot be completely emptied.
Paint cans containing paint or other cans of hazardous chemicals should be left to an environmental station as hazardous waste. Liquid nitrogen is underway to remove the paint so that the metal can be reused, which would pay off as it costs a lot of money to leave the jars for destruction.
Aluminum-laminated cardboard boxes, for example juice boxes, must be left for cardboard recycling. They go to energy recycling or material recycling. The aluminum can be separated and recycled even if it is difficult, and more development work needs to be done.
Metallized plastics, such as coffee and chip bags, should be left in the regular household garbage as they contain more than 99% plastic. There is currently no special collection of soft plastic.
Smelting
The packaging goes through a steamer before being melted and where labels, paint, plastic pieces and food debris are burnt away.
At present, the canning jars are not removed, but the tin is fused with the iron. The tin can then not be separated from the iron by refining or by any other practical method. Steel tin makes it brittle if the content is too high. Iron with a low tin content is therefore mixed. In some applications, it does not matter if the steel contains tin. The disadvantage is that the deficiency metal tin disappears from the cycle.
There are venting facilities in, for example, Denmark and Switzerland. According to calculations, it would probably be profitable to build a venting plant in Sweden as well. The sale of tin and tin-free steel would cover the costs, as well as making an environmental profit.
Doughing is done so that the canning jars are lowered into hot caustic soda and with electrolysis the tin is collected on the cathode. This method also removes food debris and labels.
When melting canning jars with food residues, it is conceivable that organic tin compounds occur. Emissions of dioxins can occur when tinned canned foods with salt residues are melted.
New Products
Of recycled metal, one can make:
- cans
- engine Parts
- Reinforcing bar
- Steel pipes
- Rims
- paint cans
- The future
Thinner aluminum cans.
The steel can get thinner tin layers.
Plastic material is used as a coating instead of tin.
Aluminum laminated cardboard instead of canning jars. For example, crushed tomatoes can now be purchased in Tetra Brik Aseptic.
Glass jars instead of canning jars.
Roll pack for eg brown beans instead of glass and canning jars. The end closures are made of aluminum.
Termination
EarthNext time you see a metal packaging, you may want to think about all the environmental issues associated with it. You will surely put in a little more effort to hand in your packaging in the right place. The metal packaging collection was the most recent packaging collection that has the potential to be the most profitable, both financially and environmentally. If we hand in our packaging, the environmental problems will not be that great, since it is the most important environmental problems at extraction and production. However, tin is a metal that seems to be ill-suited for the future cyclical community due in part to the toxic organic tin compounds.
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