the rest-impact of recycled materials

Recycled materials, once created their impact on the environment, in many forms, and if that (negative) impact is not repaired or compensated, those materials still carry an impact in a second life.

In other words , they cannot be considered impact free resources at the time of recycling, at any level. Not to mention the inputs and impacts to the recycling process itself.

Nor can you assume that the product has reached its end-of-life, i.e. counting 100% profit for recycling or reuse. Since, for what end of life? Is there a law of nature somewhere that says how long something must last? That is just an industry law, which ensures that new production is needed again. [1] In other words, there is no end-of-life, at least not a calculated or predicted one. Stuff can last a very long time if it is used sparingly, repaired and maintained. We even still find products made of glass and ceramics from Roman times. Buildings can also last hundreds of years, including wooden buildings, if properly designed and maintained. And Cuba has very many cars that are 70 years old driving around.

However, there can always come a time when something is no longer usable or repairable. And then, of course, recycling in any form is a good thing. That was also often the norm before we started using fossil fuels widely. With the ‘free’ energy from millions of years of accumulated reserves, however, we went wild, produced everything possible, repaired nothing, just threw it away. ‘There is plenty’. But those days are over, at least , we profess.

So what about the impact of recycling? That there is always a residual impact is clear from the following example: Suppose someone builds a house and sells it after one year. The new owner doesn’t like it, demolishes it and builds a new house from the same, now recycled, materials. And claims his house, the second house, is impact free because its made from recycled materials?

So the question is not whether they are impact free, but what then is that residual impact at the start of a second life?

In a construction student project, I ask students to calculate with 50% of the original impact when reused or recycled, unless it is demonstrated that the original impact has been restored or offset. But that 50% is just a flat value to make students aware, not to spend hours in research per product.

In a discussion on this within an international research group, it was argued that a developer reusing a 50-year-old building can’t be confronted with an impact legacy from 50 years or perhaps even 75 years ago? However, you can also argue the other way around that he gets a reduction on the impact of materials and building components because they are already 50 years old or more.

But the issue here is not the building or the developer, but the impact of materials on the quality of the system, the geo-physical-biological environment on which we depend.

Anyway, what might that look like more fundamentally? How would you determine or calculate the residual impact? I wrote about it before, but still without the real calculating. [2][3]

Applying materials is basically about a desired performance per unit of time, not per lifetime. So the amount of material per year of functional performance. Compare that to energy use in a house: that is a certain amount to provide a comfortable performance per unit of time. The same basically applies to materials.

Recycling or reuse then is basically nothing more than extended use. That it might changes places in between is not really relevant. The original use is extended by reuse, so in fact the original impact is spread out over a longer time. And, assuming for a moment here that the original impact has not been offset, one way or another.

An example to clarify: A building component or material in a building has an impact (energy content /embodied and/or CO2 emissions)) of say ‘X’ when first used (as per m2 floor for example). Then after 10 years the impact for delivering that function (that m2 floor) is thus 0.1*X per year of function delivery, after 50 years 0.02*X per year of function delivery: So that is the relationship between volume, time(speed) and energy of the material in the cycle and life cycle of the material.

Now what happens with recycled and/or reused, say after 50 years?

Then (suppose) a new building is made partly from recycled materials from a building that previously served e.g. 50 years. The new materials in that new building, just have their full original impact (to be called Y), as they were produced at that time. So those count 100%.

But the recycled materials have already done service, and their impact, per year of service , is thus much lower as of those new materials. Suppose the new building will last another 50 years. So then the the recycled materials will have lasted 100 years, and the arithmetic of the impact of that new building per year of function delivery, with (partially) recycled materials becomes: Y/50+X/100 (accumulated by type of material, of course)

This is how I did the math several years ago. But since then I have realized that it is nonsense to count with an end-of-life (that 50 years.) [1] Moreover, those emissions for the deployment of (new) materials are today. So for the new materials, we calculate the actual total impact. Now.

So with the years, the derived impact per m2 of function provided will decrease, calculating backwards. But you can’t start calculating forward!

Next we argue that the recycled materials , in whatever form, should last at least 50 years again. (I’ll come back to that 50 years in a moment) Then in 100 years the load of the recycled materials is 0.01 X, and so for the next 50 years another 50 x 0.01, which comes out to 50% of the original impact. (That’s how I arrived at that 50% as a lump sum for the student project.)

So for our example, that is added to the new impact: Y+ {(X/100)x50}

Of course, we don’t know if those recycled materials will last another 50 years.

What irritates me is that for the reuse part , the X, I then still calculate with a new notional life span… That can be overcome by another approach: actually setting a maximum allowable impact per m2 floor , per year (!). (for new and recycled combined) And then you can calculate what the residual value of recycling is, namely whether the previous function has already met that, and concluding what part, if any, should still be included. Suppose the maximum impact for a m2 of floor is set at 0.01*X for the function per year, and after 50 years of first use it comes out at 0.02 X, then you know that you still have to count half of the original impact, no matter how long it lasts in a second life.

We need to think about this some more. Even better would be that every material use be required to have its impact repaired, or compensated for, within certain time period. Then it is also solved: then either there is residual compensation to charge, or the starting impact of reuse is 0 if already compensated, apart of course from new process energy for recycling itself.

The ansolut best thing to do would be to relate possibilities for material and energy investments to available system potential: What is the annual sustainable yield of energy and material within the terrestrial biophysical system, and how much is (still) available for a particular function. This is being worked on and I will come back to it in due course.

But how exactly to account for this is, for the time being, still fodder for discussion. Besides, some other questions also remain: such as: is it known what original impact was? Is it known how old the material is? What unit to account in? And do we know the production impact of say 50 years ago? For that, see some notes below.

But the main point is: recycling is not free of original impact!




1) availability

Do realize that buildings actually have to ( and can) last longer and longer, (materials will become scarcer in the future) So little material will be released in future for recycling. And even with significant demolition, it is expected that recycling can never exceed 20 pct.

2) History-1 time

How do you know how long a material performed a function in its first phase of life? For an entire building that is demolished, it is usually possible to find out when it was built. But sometimes this will not be the case. Then set a legal fixed value ? ( 30 years, derived from real estate return calculations…;-)

3) History-2 impact

With how much impact was it produced at the time? This is more difficult to ascertain: which plant did it come from, what energy mix did it use? How was it transported, where did the raw material come from, from the Netherlands or, say, South America?

Here I would keep this pragmatic, and assume tav production that it was made with the general energy mix of the home country in the year of production. The quantity, of course, is obvious. Regarding transportation, assume production within the homeland.

Then it is still unclear what the actual impact was in production , that will be hard to find out: how much machinery, how much manual labor etc. Again, a pragmatic suggestion: If it is not possible to find out, or entire recalculations should be made: Take the figures of the impact that the product has today, and apply a correction factor for the (in-)efficiency of the energy mix at that time. the year of production .

4) history-3 compensation

I have assumed that in the past there was an impact, but it was not compensated. Of course, this is not always necessary: If, for example, 50 years ago a furnace was fired with wood, and the wood has been planted again and is still there today, then the energy impact has been compensated, and so there is no residual impact. So the material counts as 0 impact in recycling in terms of energy impact (the X=0) ( excluding the new energy to be invested for recycling, the Z) .

Here, of course, a huge number of variants are possible. I suggest assuming uncompensated by default, unless there is evidence to the contrary.

5) non-recycled part

the part not recycled also has residual impact ! Not for the building in the above example but for the former owner of the materials. This also has to be solved: Just dumping, before a certain performance value has been reached, in terms of function/year, or not has been compensated, should also result in a claim towards the owner, and the building owner has to pay a fine for premature disposal of that fraction.





[1] end of life:

[2] Paper World Resources Forum 2013 Davos Switzerland : via


Author: ronald rovers