Versión en español: Una discusión útil: recursos, materiales, metales y contenido reciclado
Sometimes products which are made with recycled materials are praised as “environmentally better”, but at the same time we may hear that a given product “is not very good because it was made with recycled material”.
These statements can equally be made as if they were absolute truth. It’s not just a media attitude: we all do that from time to time.
Once the useful life of a product comes to an end, it is good to be able to reuse the material, independently on whether the same or a different product is manufactured.
I’ll try to show why identifying one of the options as good and the other one as poor has not a real meaning in the sustainability debate we all are inmersed.
Throughout this process, which often starts deep in the earth crust and might end we don’t really know where, there is some confusion on what is a resource, what a material and what a product, so I will start talking about resources.
Resources are substances which nature provides us with, among other purposes, to manufacture things. Trees or other plants, oil or minerals are resources.
Water is a resource as well, even if with water alone we do not produce objects -unless we live below 0ºC in which case we could build a hut, for example- but a lot of materials contain water in their composition, and most of them require water to allow producing them.
Materials are substances which are obtained from the resources. Wood, steel, glass, policarbonate or silk are materials.
And products are useful things which are manufactured with materials. A box of cardboard for biscuits, a steel crankshft for an automibile or a glass window panel are products.
Resources can be, more or less:
Renewable, such as trees, wool or leather, which can be cut down but can be grown again -for leather, I´m afraid we have to raise a different provider-
Fossil, such as oil, which come from the earth and can be turned into materials or energy, and are not formed again –at least during the life of a human being- so to speak.
Permanent. These are chemical elements, or combinations of those elements, which retain their characteristics even if they are processed and deformed to produce things. They are also called mineral resources: we would find here all metallic elements, basically atoms such as copper, lead, aluminium or iron, and combinations of metals and other elements such as silicon, sulphur, carbon or oxygen, whose visible form are rocks, formed by combinations of oxides, silicates and other such as carbonates.
You could ask me what types of resources are used to produce materials; the answer is simple: all of them. And to produce products from those materials, it would be the same answer: all of them.
The diference between a product coming from a renewable resource and one obtained from a permanent one leads us to discuss sustainability: for a sustainable process, in the first case we have to pay considerably more attention to the management of the resource –for example assuring that there are equal number of new trees planted as the number of trees cut- while in the case of permanent materials the emphasis has to go to ensure that, once used, the material stays in the productive cycle through recycling.
There is still another difference: if a material comes from a renewable or fossil resource, during the life of the product changes take part, for example in its strength, which makes that, on recycling, we obtain products with different properties ; if the resource is permanent, such as glass or metal, we can manufacture again the same product with the same properties. The second is not better or worse tan the first case or viceversa. It is simply different.
That’s why it is important to describe the specific case of metals (with some technical warning we could say the same about glass) as far as the “recycled metal content” concept is used.
In a metallic product its properties depend basically on two characteristics: chemical composition and thermo mechanical history.
The first of these two concepts is comparatively easy to explain: it refers to the number and relative proportions of the metals which it contains (metallic materials for use in industrial applications are actually alloys of various metals)
The concept of “thermo mechanical history” is a bit more complex, but I hope to be able to put it in simple words: it means the successive heating, cooling and deformation processes a metal undergoes during the production of a given final product. For example a profile for a window frame is obtained extruding a hot metal cyclinder (in a way that metal passes through a die with the final shape of the product, not very different from the way some cakes are decorated).
If a metallic material has the same composition and has gone through the same thermo mechanical process, for a given final dimension (eg a sheet with the same final thickness) it will have the same properties eg strength, elongation, etc.
It does not matter whether the metal has come from the metal ore or from a used product, namely if the atoms which compose the alloy have been in the ore since the earth was formed or have been part of a roman sword, after that as beams of the San Francisco bay bridge and then as the radii in a bicycle wheel.
What really matters here is that, once the useful life of a product is over, the metal is recovered to manufacture the same product or something else.
Namely: knowing whether the frame of the new window you have just installed when redecorating your home is made of 30% or 70% of recycled metal is irrelevant. Not only that, by studying the material composition you cannot know it.
This concept, however, is difficult to transmit to the ordinary citizen, but it is still more difficult to transfer to a marketing department which believes that their product will be sold better – or perceived as “green”- if it indicates how much recycled metal it contains.
Thinking about how to explain this in plain terms, when someone from a drinks company asked me if I knew how much recycled metal was in the cans they bought, I fought back with this one: and do you know how much recycled water you have in the soft drink you produce?
I never thought this humble question would raise so much unrest. Actually, rather tan provoking curiosity I felt as if I had offended the person I was talking with.
“we don´t use recycled water” was the answer in not a very friendly way.
So, as I was already in a mess, dared to advance my second question: And how do you konow it?
The attitude somehow changed “we always use first quality water which is purified and treated before going in to our drinks” was the answer.
So I went on for yet another question – And how do you measure that?
“well, we measure the impurity content, pH,etc.
Finally, I asked for the last question: once you know the impurities level, the acidity (pH) or any other relevant parameters, how do you know whether the molecules of water were standing in that spring from the beginning of time, or whether they came from residual water which evaporated and was part of the rain of last year?
I dont know if I convinced the other part, but I did not get the same question from the same person any more.