High One Envrionmental ChemistryWASTE!
IB REQUIREMENTS:
  1. Outline and compare the various methods for waste disposal.
  2. Describe the recycling of metal, glass, plastic, and paper products, and outline its benefits.
  3. Describe the characteristics and sources of different types of radioactive waste.
  4. Compare the storage and disposal methods for different types of radioactive waste.


Tan Yang Jie

The definition of waste by Merriam-Webster is defined as "refuse from places of human or animal habitation.” In general, we perceive waste as something that we do not want and will discard, so as to not be associated with it any longer. As the world population grows, increase in standard of living leads to the waste levels proliferating at a high speed; about 1,000,000,000 tones are disposed each year. Many societies are focused on consumerism, which means that more and more waste is generated on a daily basis. Since the early days, our ancestors have found conventional ways to deal with waste which are modified and enhanced with technology and knowledge from the past.


Incineration:

Waste_Incineration_Plant_Schematic.png

This is the most common way of disposing waste. Incineration is the combustion of solid and liquid waste products (sometimes gaseous waste) to form gaseous products and residue. High temperature and pressure are required for the combustion and this is usually carried out in a furnace or boiler to use the energy generated to provide electricity.


Landfill:


BGS_landfill.jpg

Landfill is basically digging up soil from a large area and dumping the waste in the dug up area before covering it with earth again. This is a very old and conventional way to dispose only solid waste. The waste would then be decomposed by organisms that break down and decompose the waste.


Ways of Disposal
Incineration
Landfill
Advantage
  1. Disposes Solids/Liquids/Gases especially medical waste
  2. Used to generate energy
  3. Exterminate large amounts of waste
  4. Ashes are used in construction
  1. Disposes Solid waste
  2. Can generate methane gas for other uses
  3. Can be capped and used for construction of buildings and playgrounds.
  4. Cheaper than incineration
Disadvantage
  1. Requires specific temperature and pressure.
  2. It is expensive
  3. Emits greenhouse gases after combustion
  4. Produces ashes that consist 10%-30% of the original waste
  5. Creates dioxins, a toxic chemical
  1. Loose garbage would be blown around.
  2. Breeding area for pest and birds
  3. Lead to water and soil pollution
  4. Can lead to sinkage problems if constructions is carried over it
  5. Requires land space

Recycling

Metal:
Metals are first collected and sorted in to their composition and types before heading over to be melted. They enter the smelter which melts the metal at a temperature high enough to turn it into molten state. In its molten state, it is then molded in to ingots and set to cool.

Glass:
Glass is collected and sent on for a scan check by a magnet to pick up any metals found amongst the glass. The glass is then washed and sorted out to their respective colours as the colours have the same chemicals and mixing them up causes a contamination. The glass is then sent to be crushed into smaller pieces call cullet. The cullet is then sold to glass manufacturing company and cement companies to be reused. Companies can also melt the glass and mold it into new glass bottles.

Plastic:
The common process that is used in recycling plastic is the inverse polymerization process where the polymers in the plastic are converted into initial monomers that were used in the manufacture. These chemicals are then purified and synthesized to form new plastic materials. Assorted polymers are converted into petroleum in another recycling process. The advantage of this process is that any mix of polymers can be used. A new recycling process generates heat from the friction of plastic materials which melts the plastics. This is then pumped into casting moulds. The great advantage of this technique is that all types of plastics can be recycled.

Paper:
Recovered paper is sorted and graded then delivered to a paper mill. It is 'slushed' into pulp and large non-fibrous contaminants are removed (for example staples, plastic, glass etc.). The fibres are progressively cleaned and the resulting pulp is filtered and screened a number of times to make it suitable for papermaking. Before the recovered paper can be used to manufacture certain grades of paper the printing inks have to be removed to increase the whiteness and purity. The recovered paper is first dissolved in water and separated from the non-fibre impurities.
The fibers are then progressively cleaned in order to obtain the pulp and during this stage the ink is removed in a flotation process where air is blown into the solution. The ink adheres to bubbles of air and rises to the surface from where it is separated. After the ink is removed, the fibre may be bleached, usually with hydrogen peroxide.


Resource
Benefits of Recycling
Metal
1. Metal do not lose their properties when recycled.
2. The most commonly recycled metals are aluminium and steel.
3. Recycling aluminium requires only 5% of the energy and produces only 5% of the CO2 emissions of production from raw materials.
4. Aluminium metal is so valuable that is makes no sense to landfill it.
5. Steel is melted and turned into new car parts, cans, and structural components.
6. You can go to scrap metal recycling facilities and get paid for what you bring
7. Decreases environmental damage caused by mining
8. Reduces water pollution
Glass
1. Less energy is required to produce new glass from recycled glass.
2. Glass does not deteriorate during the recycling process therefore it can be recycled indefinitely.
3. Reduces air pollution by 20%.
4. Reduces water pollution by 50%
5. It reduces that amount of landfill space that is used
Plastic
1. Recycling plastics causes less pollution and requires much less energy to make new plastics.
2. Non renewable fuels are not tapped on.
3. Landfill plastics are reduced which helps out in land pollution.
Paper
1. Many types of papers can be recycled.
2. Reduces waste in landfills.
3. Saves trees and energy and reduces pollution from manufacturing paper

Types of Polymers and Their Uses

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Radioactive Waste

Types of radioactive waste (rad-waste)
Low-level Waste is generated from hospitals, laboratories and industry, as well as the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters etc. which contain small amounts of mostly short-lived radioactivity.

Intermediate-level Waste contains higher amounts of radioactivity and may require special shielding. It typically comprises resins, chemical sludges and reactor components, as well as contaminated materials from reactor decommissioning. Worldwide it makes up 7% of the volume and has 4% of the radioactivity of all radwaste.

High-level Waste may be the used fuel itself, or the principal waste separated from reprocessing this. While only 3% of the volume of all radwaste, it holds 95% of the radioactivity. It contains the highly-radioactive fission products and some heavy elements with long-lived radioactivity. It generates a considerable amount of heat and requires cooling, as well as special shielding during handling and transport. If the used fuel is reprocessed, the separated waste is vitrified by incorporating it into borosilicate (Pyrex) glass which is sealed inside stainless steel canisters for eventual disposal deep underground.

Waste disposal:
Low-level Wastes are buried in shallow landfill sites. To reduce its volume, it is often compacted or incinerated (in a closed container) before disposal. Worldwide it comprises 90% of the volume but only 1% of the radioactivity of all rad-waste.

Intermediate-level Waste may be solidified in concrete or bitumen for disposal. Generally short-lived waste (mainly from reactors) is buried, but long-lived waste (from reprocessing nuclear fuel) is disposed of deep underground.

High-level waste final disposal, is delayed for 40-50 years to allow its radioactivity to decay, after which less than one thousandth of its initial radioactivity remains, and it is much easier to handle. Hence canisters of vitrified waste, or used fuel assemblies, are stored under water in special ponds, or in dry concrete structures or casks, for at least this length of time.

The ultimate disposal of vitrified wastes, or of used fuel assemblies without reprocessing, requires their isolation from the environment for a long time. The most favoured method is burial in stable geological formations some 500 metres deep. Several countries are investigating sites that would be technically and publicly acceptable, and in Sweden and Finland construction is proceeding in 1.9 billion year-old granites.

One purpose-built deep geological repository for long-lived nuclear waste (though only from defence applications) is already operating in New Mexico, in a salt formation.

After being buried for about 1000 years most of the radioactivity will have decayed. The amount of radioactivity then remaining would be similar to that of the corresponding amount of naturally-occurring uranium ore from which it originated, though it would be more concentrated.


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