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Energy - Cost
General Information
Physical Insights
Example Uses
Simple Questions
Further Questions
This chart gives a useful for a first look at the trade-off between environmental concerns over excess energy use and the cost penalty.
General Information
In general the energy required to produce a material is a large factor in the raw material cost. As a result most materials lie on a line from bottom left (low cost/low energy content) to top right (high cost/large energy content).
It is difficult to assess the environmental impact of using one material over another since there are many factors from production to disposal.
The energy content used to produce a material gives a rough indication of the environmental cost of production
For materials which are energy intensive to produce there are large cost and energy savings by recycling e.g. aluminium cans
Gold is a precious metal which can be sold for a very high price; this means that more energy can be spent in extracting it by mining rocks containing only a small fraction of gold
Physical Insights
Measuring the energy content of a material is difficult, but includes:
the energy required to collect/mine the material.
the energy required to refine, extract or synthesise it.
Polymers are made by refining and processing hydrocarbons from oil - the energy used per kilogram is similar to the energy needed to produce many metals
Construction materials such as concrete, brick and woods require relatively little energy to produce them and are thus cheap and less environmentally damaging.
Metals are usually extracted from their oxide - this takes up a lot of energy, for example, one twentieth of the total energy consumption in the United States is used to produce aluminium.
Example Uses
To select materials which have less environmental impact and contribute less to global warming
To consider environmental impact for one-use disposable products - e.g. disposable gowns, sheeting etc in hospitals are made from paper
To consider environmental impact for high volume, energy-intensive products such as cars
Simple Questions
Why is it economic to recycle aluminium cans but less so for steel ones?
Steel cans are very common in the food industry (baked bean cans), while aluminium cans are dominant in the beverage market. Steel is relatively cheap to produce in energy costs, making it uneconomic to recycle in the small quantities offered by food cans, Aluminium however is very energy intensive to produce giving big savings on recycling.
Why will new reserves of minerals/oil which are not now economic to mine become economic in the future?
The cost of minerals/oil reflect current availability. As resources become scarce the price rises, making recovery from more difficult to access or less plentiful sources more economic. For this reason it is very difficult to predict the extent of current reserves. Most text-books on resources written in the seventies predicted we will have exhausted many resources by 2000. This is one reason why this is not the case.
Select materials for a wall/fence around your house.
Your choice may depend on where you live. If you live near a source of suitable stone then it is likely that many houses will have stone walls and a stone wall becomes both an economic possibility and an aesthetically pleasing one. Otherwise wood (sustainable) or a wire fence may be an alternative.
Select materials for fast-food restaurant eat-in plates, trays, etc
A wise choice is important for the environment and costs of dealing with all the rubbish. Expanded polystyrene should be avoided and sustainable paper and card is preferable.
Select materials for bedding for cattle.
Not all questions are answerable using charts! Traditionally straw is used which is energy efficient and sustainable since it is the by-product of corn production. Another green alternative would be to use recycled paper cuttings which could then be simply added to the silage.
Further Questions
Why doesn’t energy produced by wind-turbines lead to global warming?
Why is the controlled burning of polymers an environmental option to landfill?
Give one application where diamonds are used in industry and explain why.
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