Ann's geography blog: The Recycling Center

Once your green bin is collected by your bin company's waste collection vehicle it is then brought to another area where it can be sorted out. This also happens to the rubbish at your local recycling center. This sorting allows various materials to be separated into isolated groups- glass, plastic, paper, cardboard and metals.

Waste Collection Vehicle

Source-http://www.archive.fitzroyshire.qld.gov.au/services/Services_Environmental%20Services.shtml

The main facility used in Dublin is the Materials Recovery Facility located in Ballymount, Dublin 12. The waste is put through different separation steps by a conveyor belt. Large plastic bags and pieces of cardboard are removed at this stage as they can jam the machine. The machine then sorts through the waste by weight. Paper, cardboard and plastic are separated from the heavier glass and metals.

Glass on a conveyor belt.

Image taken from- http://www.co.greene.oh.us/saneng/EnvServ/Recycling_Center_Glass_Info.htm

Cardboard, paper and plastic are then separated into groups. This sorting used to be done by hand but now a spectroscopic scanner can differentiate the different types of plastics and paper based on the wavelengths at which they absorb light. Each material absorbs light at a unique wavelength so the scanner can identify the composition of the waste.

Large magnets can differentiate the metals. The ferrous metals (iron, steel and tin cans) get lifted up by this magnet. Non-ferrous metals are grouped by magnetic eddy currents. An example of a non-ferrous metal would be aluminium cans. A rotating magnetic field creates a electric current around the can which creates a magnetic eddy current inside the can. The eddy current is repulsed by the magnetic field, so aluminium cans are separated from the rest of the waste. Finally, glass has to be sorted by hand based on the colour it is.

After the items are separated into the correct groups they then are changed so they can be reused for other materials. Below I have explained the process of the three main items we recycle- plastic, paper/cardboard, and aluminium cans.

Paper

Once the paper is separated it is then shredded. Water is then added to create a "fibrous pulp" from the paper. Wood pulp is also added. After this the paper has to be cleaned and all objects have to be removed, such as paper clips, staples, and dirt. They are removed by filters and special cleaning techniques. The ink is then removed. The remaining paper is passed through a drying machine on a roller, causing the fibres to join together. After the fibres have joined together and are dry, it is rolled onto large reels and now is recycled paper ready to be sent to the factories. The quality of paper decreases everytime it is recycled, so more wood pulp must be added eventually or else the recycled paper is used to produce less high quality products.

Plastic

The plastic is first washed and chopped into flakes. It is sorted into various types of plastic by putting it in a floatation tank where the heavy plastic sinks and the light plastic floats. These flakes are then put in the tumble dryer. After they are dried they are entered into an extruder which causes the plastic to melt. The plastic is put through a fine screen removing any unwanted particles that it could contain, then it is formed into strands. The strands are left to cool in water then they are chopped to make uniform pellets. Factories use these plastic pellets to make products. The pellets also can make flowerpots and be used for carpeting.

Plastic

Source-http://www.greenstarkville.org/green_living/recycling/imgs/plastic.jpg

Aluminum Cans

The cans are condensed by squashing them together to make briquettes. These are then sent to aluminum companies for melting. The cans are shredded and then crushed. By using a burning method the inside and outside of the cans are removed. The recycled aluminum is mixed with completely new unused aluminium. The molten aluminium is poured into ingots that are 25feet long. The ingots are then rolled so they are not too thick. After this the metal is made into cylinders and sent to can makers that produce the lids and bases. The new cans are used to hold drinks and sold in shops.

Aluminium Cans