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Author Topic: Energy costs in recycling  (Read 7167 times)

paul.fr

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Energy costs in recycling
« on: 12/03/2007 05:12:41 »
Recycling is good for the enviroment, we all agree on that. But any recycling still uses energy.

In terms of energy used which is more efficient. Recycling Aluminium or Glass?


 

another_someone

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Energy costs in recycling
« Reply #1 on: 12/03/2007 10:45:43 »
Recycling is good for the enviroment, we all agree on that.

Do we?

Lots of assumptions there, both about people, and about what is the Environment, and that there is such a thing as 'good for the Environment'?

When one uses words like 'good' or 'bad', I start thinking we are talking about religion rather than science, and I often suspect that much of environmentalism is more about myth and faith than real science.

But any recycling still uses energy.

True, and it also involves often chemical processes as well.

Quote
In terms of energy used which is more efficient. Recycling Aluminium or Glass?

Depends from what you are recycling it, what use you intend to put it to, and where you are collecting it from, and how you collect it.

A fair about of energy is consumed simply collecting material from households for recycling, but collecting bulk material from factory waste for recycling is far more efficient in terms of energy.

In the old days, we used to recycle milk bottles by simply collecting the bottles, and the only processing involved was washing the bottle out, and immediately reusing it - that was as an efficient form of recycling as you can get.  These days, all sorts of glass is mixed together (although nominally segregated by colour), so simple reuse is not possible.

In general, transport costs aside, the biggest variable you have to worry about is the purity of your source material (and how pure you need that material for its end use).  Recycling, aside from the cost of actually making the finished article (which is the same as if you are making the finished article from non-recycled material) is primarily a purification process, and the purer your original source, the easier it is to recycle.  So, an aluminium can with a steel top is more problematic than a pure aluminium can.  All of this means that recycling from industrial sources, where you know exactly what the source material is, is always easier than recycling from domestic waste, where you have very little control over the purity if the material you are recycling (often the householder themselves is unsure of what materials the waste they are disposing of consists).

Ofcourse, transport cost is a big issue, and one of the problems with glass is that for its given structural strength, it is quite heavy as a packaging material, and so it carries a high transportation cost (this is one of the environmental arguments in favour plastics as a packaging material - the low weight reduces transportation costs).

The other factor is, how do you judge the value of human labour used in the process.  The largest use we make of high energy devices is in ways of saving our own labour (i.e. that human beings are able to do more in a shorter period of time).  If we are spending lots of human labour in the recycling process, does this force people to use more energy in order to recover that time in other ways, and would not as an efficient way of saving energy be simply to give people more time in their lives to do ordinary things, and so be less dependent of, high energy, time saving devices?
« Last Edit: 12/03/2007 11:08:43 by another_someone »
 

paul.fr

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Energy costs in recycling
« Reply #2 on: 12/03/2007 11:17:33 »
you are quite right, a bad choice of words on my part.

I was basing the question on aluminium drinks can, which we are encouraged to recycle either for collection by the refuse collectors or that we deposit in those large recycling "banks". As opposed to glass bottles, be them milk, beer or anyother liquid they contained. Again for collection in the same way as aluminium cans.

If we forget about the transport and manual labour costs, which uses more energy to recycle? The melting of the aluminium or the glass?Then the energy costs to remake the can or bottle.

Another question could be which uses more energy in the first place, ie to make the very first can or bottle?

If i remember correctly, feel free to correct this, aluminium uses vast amounts of energy in the first place. From the mining of the bauxite through all the processes until it is eventually baked.

The exact industrial process for making glass i can not recall.

« Last Edit: 12/03/2007 11:20:48 by paul.fr »
 

another_someone

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Energy costs in recycling
« Reply #3 on: 12/03/2007 12:25:41 »
I believe the energy cost of processing bauxite is quite high, while the cost of actually melting aluminium is very low (aluminium has a fairly low melting point - but then, so does glass).  In pure energy terms, glass is probably cheaper to produce from sand (after all, humans have been doing it for millenia, albeit the quality of ancient glass was rather poor; while aluminium was not commercially produced until the 19th century).

In both cases, I don't think the cost of melting the product (unless one is talking about specialist glasses, such as Pyrex) is going to be the major portion of the cost of recycling.
 

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Energy costs in recycling
« Reply #3 on: 12/03/2007 12:25:41 »

 

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