MATSE 81
Materials in Today's World

Recycling

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Recycling of used products rather than disposing of them as waste is a desirable approach for several reasons. Recycled material replaces the need to extract raw materials from the earth. The energy requirements to process recycled materials are normally less, and in the case of aluminum much less, than the energy required to process extracted raw materials from the earth. In addition, recycling conserves natural resources and eliminates the ecological impact from the extraction of raw materials from the earth. Proper product design facilitates recycling, which reduces pollution emissions and landfill deposits.

Some issues surrounding recycling include that products must be disassembled or shredded to recover materials, and collection and transportation costs are significant factors in the economics surrounding recycling. The following video examines the anatomy of a properly designed landfill. After watching the video (4:39), proceed to your textbook and read section 20.5.

To Watch

Landfill video

Click for a transcript of Landfill. This will expand to provide more information.

Whenever you throw away your rubbish, do you ever wonder where it goes, what happens to it, and the effect this can have on the environment? The answer is that everything has not been recycled or reused ends up in a landfill site. What do you think this means? If you think that a landfill is an open hole in the ground where we bury the rubbish you'd be wrong. In fact it is a carefully designed structure built into or on top of the ground to store your rubbish in such a way that it will be isolated from ground water. Our fresh water supply will be kept dry preventing leaking into this groundwater and will not come into contact with the air causing horrible smells. This isolation is achieved with a bottom liner typically made from very thick PVC and a daily covering of soil. However, in many countries open rubbish tips still exists causing environmental and health problems. If our rubbish is isolated from the surrounding environment it doesn't decompose. Landfill sites are not like a compost pile where the purpose is to bury rubbish in such a way that it will decompose quickly. Rather, landfill sites are simply a way that we cope with the vast amounts of rubbish that we produce.

Let's now take a look at the parts of make up the landfill cell and how these cells make up organized landfill sites. Ground water has to be protected from chemicals found in our waste and so compacted clay is placed on top to act as a physical barrier. On top of this is a very thick waterproof plastic liner. This stops water that contains waste chemicals called leachate from contaminating this ground water. A geotextile mat, typically made from polypropylene or polyesters are like a woven fabric, and this too prevents plastic sheeting from being damaged when a shark gravel layer as the rub on top is compacted. The gravel layer on top of the geotextile map filters large pieces of debris allowing only water through. this improves the drainage of the landfill cell. The gravel layer is connected to a leachate pipe. The leachate is collected through pipes where it goes into a leachate pond. This leachate a can't be used as drinking water and needs to be treated like sewage before it can be moved on the sites. This must continue even when landfill site is full. A drainage layer and the soil layer prevent firming from entering landfill cells. Finally on top of the landfill cells old-new is where buried rubbish is compacted by heavy diggers of machinery. Bacteria in landfill break down the trash under anaerobic conditions meaning in the absence of oxygen and so a byproducts of this breakdown is landfill gas. This presents a hazard because this gas contains methane which could explode therefore, it has to be removed.

To do this the series of pipes are embedded within the landfill to collect the gas and some landfills this gas is vented or burned. What do you think might be a better use for this gas? Pause the video and continue when you're ready.

If you said that the methane in landfill gas could be used as an energy source you'd be right. This means it could be collected and burning boilers to generate electricity.

In summary, a landfill is carefully constructed and allows waste only to be stored. It may never decompose and is not really a viable solution for dealing with waste. In addition extensive monitoring is required to ensure that no leachate a escapes into the groundwater. This has to happen even once a land that is no longer in use. There aren't really any upsides to landfill where the gas produced can be collected and balance of fuel, it can also cause explosions if not vented properly. So we need ways to recycle, reuse, and reduce.

To Read

Read section 20.5 in the customized e-book.

In the next sections, we will be discussing the recycling of metals, glass, polymers, paper, and limits of recycling.