Chemguide: Support for CIE A level Chemistry

Learning outcome 4.3(b)

This statement is about finite resources and recycling.

Before you go on, you should find and read the statement in your copy of the syllabus.

I would be surprised if you had got to this point in your education without already having discussed this sort of topic to the point of boredom!

Anyway . . .

A finite resource is one which doesn't get replaced at the same rate that it is used up. For example, copper is a finite resource.

Copper makes up about 0.006% of the Earth's crust, and is a valuable metal with an annual extraction of about 15 million tonnes across the world.

Note:  These figures come from a table on Wikipedia. Obviously the percentage value can't be anything more than an estimate, which is why Wikipedia quote a number of similar, but different, values from different sources.

If production continued at the same rate, and no new sources of copper ore were found, then obviously the world would run out of copper ore. In the real world, of course, as existing supplies of the ore get more scarce, the price of copper goes up, and it becomes economically worthwhile to extract copper from less rich or more difficult sources. It would also be worthwhile to find new materials to replace copper.

That, of course, just delays the problem, and eventually easily extractable sources of copper will run out. Copper is a finite resource.

Oil is another obvious finite resource. It takes millions of years to form, but is being extracted and used in a very much shorter timescale.

Aluminium is another frequently quoted example. Aluminium actually makes up about 8% of the Earth's crust - it is the third most abundant element. It is inconceivable that you could actually use up all the aluminium that is present in rocks and soils throughout the world, but you still count aluminium as a finite resource.

The problem here is that to be worth extracting, the aluminium has to be concentrated in an ore, such as bauxite. It is no use if it is spread in a relatively dilute form everywhere. It would be too difficult to process sources like this into the aluminium oxide from which the aluminium is extracted.

Renewable resources include things like wood. It is possible to grow new trees to replace those that are cut down. As long as you can replace them as fast as they are used, trees are a renewable resource.

Biofuels such as ethanol made by fermentation of suitable crops are also renewable resources.

Recycling attempts to slow down the rate at which resources are used up, and it may also be cheaper to recycle material than to make it from scratch. Recycling can also reduce environmental problems.

Aluminium is often quoted as a good example of something which can be recycled. Manufacture of aluminium from its bauxite ore is very energy intensive and expensive. It is much cheaper to recycle aluminium by remelting it and turning it into new products than to produce the aluminium from scratch, because recycling needs much less energy.

Note:  You will find a detailed explanation of the extraction of aluminium and some notes on recycling it on this Chemguide page.

Important:  In an exam answer, you wouldn't get any credit for saying that "It is cheaper to recycle aluminium than to produce it from the ore." It is too vague. You would have to explain why it was cheaper, in terms of recycling not needing as much expensive energy.

Recycling glass is useful for much the same reasons.

You can find out more about the recycling of various materials from the US Environmental Protection Agency website. This link will take you to a list of materials that you can get more information about. The EPA is probably more concerned with preventing waste from causing environmental damage than saving resources.

There is also some useful information from the UK site Waste Online. The articles on glass and metal recycling are both helpful.

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© Jim Clark 2010 (last modified March 2014)