TL&DR Summary: all real systems have energy and matter inputs, and generate waste streams of both matter and “entropy” (i.e. the entropy of the universe always increases). A “circular economy” is a thermodynamic impossibility. We should instead talk about optimal recycle, where the environmental impacts of matter waste are balanced against energy input and its associated impacts. As our energy system becomes cleaner, the optimal recycle will increase.
So, why is a ~27 ton excavator parked in front of a cute little Toronto bungalow?
No, Arthur Dent isn’t lying in front of it in his bathrobe. Rather, this perfectly liveable home, built likely just after WWII, is about to be demolished, to make way for what we affectionately know in the neighbourhood as a “McMansion”- a building built within an inch of every dimension permitted by local zoning, plus whatever extra they can get via a trip to the Committee of Adjustment, designed to maximize resale value by having as much floor area and indeed also as much interior volume as possible. Aesthetics? Function as a home? Good sense from an urban planning perspective? Nah. Those are all second thoughts at best!
Demolition is dangerous work. Taking a house apart piece by piece to permit recovery and re-use of those components worth salvaging used to be done by hand, by people with crowbars and sledge hammers. Or, in rural areas, with a can of kerosene and a match… I have fond memories of going to the salvage yard, Teperman’s, outside Kitchener Ontario with my father, where he would buy planks sawn from old growth trees. Planks salvaged from factories built in the 1800s that they had torn down- lumber that simply doesn’t exist in Ontario any more and never will again.
But labour costs too much now, and machines make this work much less hazardous.
What will inevitably happen is that an excavator operator will smash this house, often complete with contents left behind by the former owner, and sort the rubbish into piles using the “fine” control of the excavator “thumb”. Wood will go in one pile, if space allows- masonry and brick in another, and whatever metal that can be salvaged- wire, pipe, aluminum eavestroughs etc., into yet another, much smaller pile. It is rare for a worker to set foot outside the excavator the whole time.
The wood might be recycled, after a fashion. Wood waste in Toronto is sometimes taken to a facility where it is shredded, nails and all, and the wood shreddings are used for paper-making.
The brick, concrete and masonry are destined for landfill. The Leslie Street spit which extends into Lake Ontario, consists of a lot of this kind of fill- in fact, much of the land south of Front Street in Toronto is “lake-fill”, not native soils. Unlike the concrete from large buildings, which is often ground up for re-use, there’s too much diversity in materials in the masonry waste stream from house demolition to make it useful even as aggregate for making new concrete, or as road bed material.
All the roofing, drywall or lath and plaster, insulating materials- foam, mineral fibre or fibreglass etc., and a host of other material, will go to landfill. And as long as the wood and other biodegradable materials have been sorted out adequately by the clever excavator operator, most of these materials will simply remain in landfill for millennia, with no ongoing environmental impact. But of course, the sorting isn’t perfect, as people are in a hurry and equipment is expensive, and so the potential for that wood and paper construction material to very slowly degrade to methane and CO2 in the landfill is very real.
Circular Economy- An Ideological Concept
Most of us just aren’t all that curious about what happens to our things at their end of life. We toss them into a bin, or hire a contractor to do demolition, and don’t give it much thought after that.
But there are some people who have a different notion. They’re selling us on a concept called the “circular economy”. And that concept is often sold with a diagram like this:
Sadly, what the diagram is missing some important things. Here’s a more accurate representation:
I’m a scrounger and salvager by nature and nurture- and I’m also cheap. As a child I would accompany my father to the local industrial metal scrapyard where he would salvage electric motors and steel for his projects, and I came face to face with the realities of industrial recycling. So much waste! So much potential for re-use, squandered. I remember sharing my father’s disgust to see brand new electic motors, still in their cardboard boxes, that somebody had taken the extra effort to smash with a sledgehammer before throwing them into the scrap bin- the thinking being that if they didn’t have a use for them, they were damned if anyone else would gain the benefit! So there’s no need to preach to me that the notion of “circularity” should include the low energy processes of re-use and re-purposing. I live those principles, and wish the rest of our society were less driven by laziness and self importance and aesthetics. But then again, if they were, I’d find fewer treasures on the side of the road on garbage day, and that would deprive me of both cash and pleasure.
But when we’re talking about a product as heterogeneous as a house- at a certain point, the land occupied by a 1950s bungalow is worth more WITHOUT the bungalow on it, than it is with it- because it saves the future owner the cost of demolition and disposal. Things do change, and nobody who built a 1950s bungalow during the post-war boom, was thinking about anybody trying to live in it in 2025. The reality is, we do have to think about end of life demolition, and make smart decisions between recycling and disposal.
If we want to reduce how much matter in any system goes to waste, we’re really fighting a battle against the 2nd Law of Thermodynamics- the important law that says that for any expenditure of energy, the entropy of the universe must increase. A house is an example of a modern product: a complex mixture of numerous materials, each optimized to deliver the features and functions desired at as low a cost as is considered reasonable. And over the ~ 70 years since that particular house was likely constructed, our methods and materials have changed, as the costs of labour and materials and the energy they embody has changed. So it’s really a dog’s breakfast of materials- even moreso when for labour cost and safety reasons, you smash the whole thing into a heap with a giant excavator.
Take, as an example, the demolition waste from my own major home renovation project. I added what amounted to a new house to our existing house, while we were still living in it. At various points in the process, I had to demolish parts of the old house to tie it together with the addition. I could have hired a bin and just chucked everything into it, but that would not only have been a waste of materials, it would have cost me a “tipping fee” for the weight of mixed waste that had to be hauled off to landfill. So, to make myself feel better, being a bit of an enviro-masochist combined with hereditary frugality (cheapness, really…) I dutifully separated out all the wood from the plaster, drywall and other junk, cut it into firewood sized pieces, and stacked it in a giant pile in my backyard. That wood waste fueled my workshop’s woodstove for the next couple of years, and I pulled seven gallon pails full of nails from the ashes. We often joked that the guy who built our house in the 1920s, must have had shares in Stelco (the local steel mill which made most of the nails used in the province in the last century). We also re-used the original Don bricks from the side of the house, to re-brick the front of the extended house. Knocking those bricks down one by one with a deadblow mallet, and cleaning them – all 900- was a real pain in the ass at the time, but it the end result looks amazing and in hindsight it was a great decision. As was the decision to hire a bricklayer. The first 100 houses you brick, you don’t want to be your house- or visible from your house!
Of course, if the local laws permitted me to toss the debris over my neighbour’s fence and get away with it, I might have been sorely tempted to do so. Hence, there is environmental value in a landfill tipping fee for any waste that might be generated. (Aside: we lack such a tipping fee for using the atmosphere as a giant “air-fill”, or public sewer, for the effluent from fossil fuel combustion, and hence we need a “tipping charge” in the form of carbon pricing to discourage the continued emission of fossil GHGs. Otherwise, decarbonization is trying to fight economics, and decarbonization usually loses)
Recycling: A Systems Overview
All real systems, including all “natural” (biological) systems, take a matter and energy input, use the energy to transform the matter in some way, generate a product or service, and generate both a matter waste stream and, in a sense, an “entropy” waste stream, generally in the form ultimately of heat. Systems can be and often are, heavily coupled, with the waste stream from one process being the matter stream or even the matter and energy inputs to another system.
But the recycle in all real systems is never 100%. Why is that? The 2nd Law. The 2nd Law establishes an energetic penalty for the perfect separation and recovery of matter from any real process. That penalty can be small, moderate, large, or positively enormous, depending on the nature of the materials and process and what purities or levels of recovery are required.
So the greater the recovery or purity or both required, and the greater dilution of the valuable material in the source, the greater the energetic penalty associated with recovery.
Some systems are simple enough that we can calculate a minimum necessary reversible energy input required to separate, say, salt water from fresh water. Producing fresh water from seawater takes about 1.5 kWh per m3 of freshwater, assuming a reject stream which is about 50% greater in salinity than seawater. However, there are always irreversible, 2nd law losses associated with all real processes. In the case of reverse osmosis water purification, we can actually achieve that separation for about 3.5 kWh/m3, which is astoundingly good. What that also means is that no process we will ever invent, will reduce that 3.5 kWh/m3 to 1.5 or lower. No magical membrane will ever increase the energy efficiency RO by a factor of three, much less a factor of ten.
And since all energy generation and use and transformation comes with environmental, economic, social and political impacts, there’s no such thing as a free ride from recycling. As we try to increase the recycle rate, the energetic penalty will often grow to a point where any increased recovery generates more impact from energy use than it saves in terms of impacts from disposal of the waste stream.
But hey, we’re humans- and humans have a demonstrated tendency to prefer large but invisible problems, to smaller but more visible ones…We can’t see GHG emissions, so we think they don’t matter!
If we care about the environment, truly, that’s a very human tendency that we need to fight- with our brains, by doing proper analysis.
Optimal Recycle
Since true “circularity” is basically ideological nonsense in the form of a meme, abhorred by the laws of thermodynamics, we need a better concept.
The replacement concept that I think we should reach for is “optimal recycle”.
The optimal recycling rate of anything, is the recycling rate that generates the lowest lifecycle impacts, taking into account the production of new material, the disposal of wastes, the value of the new use for the recycled material if that use is different (which it frequently is) than the original one, and importantly- the impact of the energy use and emissions therefrom.
Something should become fairly obvious fairly quickly, and that is, the optimal recycle rate- while it will NEVER be 100%, will certainly increase for most things as we reduce the impacts associated with energy production and use. That is yet another advantage of pursuing a cleaner, decarbonized energy system.
The other thing that should become obvious is that it’s not easy to determine what the optimal recycle rate actually is. To do so requires a lifecycle analysis, and such analyses must be done in accordance with a standardized methodology to avoid being taught to quack like a duck for whoever is paying for the study.
Down-Cycling Versus Recycling
An example of optimal recycle thinking is the way we already recycle copper. Metals have the advantage that they’re just atoms- there’s nothing stopping us from collecting them and re-using them. Copper mined by the Romans is still to be found in modern copper articles. Old copper atoms aren’t damaged in any way by that recycling.
What does change, however, is purity. And we don’t needlessly fight the entropic battle of returning all items to their original purity, because that would have a huge energetic and hence economic penalty associated with it.
So: we don’t recycle old copper wire into new copper wire, because very small additions of other atoms into copper, reduce its electrical conductivity.
Instead, we recycle copper wire into other copper products, where small amounts of contaminants or alloying constituents don’t prevent the re-use, and may actually be necessary anyway. An example is copper pipe and tubing.
And so with copper pipe and tubing: we recycle it not into wire or pipe, but into brasses and bronzes- copper alloys which can tolerate even more contamination.
Only at the very bottom of this “down-cycling” purity chain, do we re-dissolve the products and purify them again by hydrometallurgical steps and “electrowinning”- the process of recovering and purifying copper by electrochemical recrystallization. The result is very pure copper, suitable for making wire or anything else we may desire- but there are losses, and the energy requirement of that step is huge. And there are still wastes generated- lead, zinc, tin, nickel, phosphorous, aluminum, iron and other metals that end up in the copper waste stream, all have to come out- and a similar entropic battle has to be fought to recover them into useful forms, or else they have to be chemically stabilized to be disposed of as “tailings”.
There’s nothing fundamentally wrong about “down-cycling”. In fact, it’s just good engineering and environmental practice. It’s also commonsense- it’s what our ancestors did with nearly everything, because everything took so much human labour and effort to produce. When energy became inexpensive because we learned how to mine fossils and burn them, all sorts of consumption that our ancestors would have seen as abject idiocy and decadence, became learned “normal” behavior.
Plastics
Plastics represent an even greater challenge. Unlike metals, plastics are molecules, and molecules can be damaged by heat and UV light and oxygen exposure. This can change mechanical properties, colour, or generate toxic or otherwise noxious materials that can end up in the products made from this material. Plastic molecules, being long chains, are also deadly difficult to separate from one another once they are intimately mixed. Plastics also often contain additives- plasticizers, UV stabilizers, antioxidants, stiffeners and other fillers- which render recycling difficult. And small amounts of one polymer can render the properties of a “blend” with another, unsuitable for any purpose.
And then there are “composite materials”, made of crosslinked molecules and structural fillers. Things like rubber tires and fibreglass boats. These materials, being one big molecule, basically cannot be meaningfully recycled. While limited repurposing/re-use potential for rubber crumb from chipped rubber tires, for instance, is possible and sensible, ultimately the optimal recycle rate of composites is very near zero. That however does not mean that they are an environmental disaster if used appropriately- quite the opposite can in fact be true. Witness the enormous amount of fossil GHG and toxic emissions that can be offset by a set of wind turbine blades which, after 20 years of service, need to be landfilled because they have exceeded their safe fatigue life limitation.
While I have no objection to slicing them up into pieces that are re-usable for whatever function smart people can put them to, I certainly would NOT stop us from using wind turbine blades even if 100% of them had to be landfilled! That would be the sort of mindless, ideological, nirvana fallacy-based “circular economy” thinking that frankly boils my blood.
Pure thermoplastics recovered relatively pure and easily cleaned, can sometimes be mechanically recycled right back into their original uses- in a blend with fresh material. PET plastic bottles, for instance, frequently contain some post-consumer recycled content, despite the need for purity due to its food grade use. They can also be recycled into carpet fibre and other valuable products. PET is therefore quite valuable as a plastic recycling feedstock.
Not so with the big dogs of the polymer industry, polyethylene (PE) and polypropylene (PP). While pre-consumer recycling of all thermoplastics is common, with molding sprues and mis-molded parts being re-ground and mixed back into the feed, post-consumer recycling of PE and PP generally produces quite low value products, again often blended with fresh plastic material. Examples include pallets and other dense packaging materials, plastic decking, railroad sleepers and the like. Only a small fraction of PE and PP collected for recycling, end up in valuable products.
And no, converting plastics to energy (i.e. incineration or “air-filling”), either directly or indirectly via making syngas or liquid fuels from them, isn’t “recycling”, it’s converting a fossil fuel into a smaller quantity of another fossil fuel.
https://www.linkedin.com/pulse/waste-energy-fuels-great-greenwashing-machine-paul-martin
Chemical recycling of some plastics is possible, but needs to be viewed with every bit as much a jaundiced eye as waste to energy or fuels schemes.
The key with plastics is that their ultimate end of life options are either incineration or landfilling. And while the former seems to be popular in places that are very precious about their land use, the latter actually generates the lowest end of life environmental impact. Landfilling baled, separated waste plastics that are too dirty and mixed to be mechanically recycled, is with certainty the lowest cost post-consumer fossil CO2 sequestration strategy imaginable. All we need to do is not burn it. In landfill, protected from oxygen and sunlight, plastics will remain essentially unchanged for millennia. They don’t generate leachate or CO2 or methane- or “microplastics”, if you happen to be scared of that particular bogeyman. Perhaps future generations will find these materials useful- but in the meantime, they’re doing no harm in landfill.
Design for Re-Use and Right of Repair
It seems logical, at first blush at least, to regulate how articles are designed and made, to extend their useful life and to make their handling at end of life easier.
There are plenty of examples we can find in our everyday lives, of products that seem to be designed with pre-programmed obsolescence, or which are made using such absurd assembly processes that repair is next to impossible. Cellphones, for instance, used to have removable batteries so they could be swapped out with charged ones, or replaced when they go bad. And there are examples where manufacturers take measures to prevent the repair of their goods, justified largely by trumped-up concerns about liability.
What isn’t being said, however, is why certain design decisions and material choices are made in the 1st place.
The main reason that cellphones lost their removable/replaceable batteries, was to make them thinner, and also more water resistant by means of water-tight, glued construction. This frustrates repair, but also means fewer people with their phone in a bag of rice in the hope to recover its function after an accidental dip in the water.
I certainly would like to know that the products I buy have parts available so I can repair them, and use methods of assembly that allow repair to at least be possible. Then again, I’m an engineer who grew up taking things apart and putting them back together again to see how they work, and repair – especially of goods salvaged from other people who lacked the skill or knowledge or time to do it themselves- became a matter of personal pride. But rather like with demolition, the cost of skilled repair labour has become stratospheric, rendering repair rather than disposal/recycling frequently an economically fraught decision. While YouTube has taken some of the fun out of diving into a dead product with a screwdriver and prayers or oaths, knowing that the patient is already dead and hence can’t really be harmed anyway- online retailers make access to repair parts that were formerly next to impossible to obtain, now just a roll of the dice as to whether or not the advertised compatibility with your model of thing is actually true. Self-repair of many things is definitely still a viable option. But you have to want to do it…the motivation, skill and free time to do that, run in short supply in our society.
The thing that people seem to be missing, though, is just how much engineers pride themselves in using the optimal material and method for the job- and how little control they have over the objectives of their clients or employers. And all design decisions are an optimization exercise, weighing cost of materials, cost of transformation labour and energy, and how important the various design specs are relative to one another- weight, safety, energy consumption etc. We as a society definitely have a right to weigh into that already complex decision making matrix with our own values related to energy use, waste disposal and other environmental impacts- but we’ll need to tread carefully or we are likely to make things worse rather than better.
Tying engineers’ hands with more regulatory controls which limit their range of choices, might in fact make the world a better place. But it would likely do so by making goods more expensive, so that we just buy less stuff. It likely wouldn’t fix the learned propensity of people to throw things away when they don’t work any more. That’s been learned now for many generations.
One regulatory control I’m a bit in love with is deposit-return. It works brilliantly with lead-acid batteries, ensuring that around 99% of them end up returned for proper recycling, rather than adding lead contamination to landfill leachate. Win-win. But if we apply deposit-return to everything we make, expect costs to skyrocket, and anticipate more than a little environmental impact from all the very sub-optimal transport required to make that happen. Like all regulatory controls, it needs to be applied with a brain rather than ideologically.
Conclusions
If you’ve made it this far, you likely care at least as much about these issues, and about getting them right, as I do. And you’ll hopefully understand that reality is much more complex and less clear than a simple meme- slogan like “circular economy”. Perhaps you’ll also be just a little better prepared to discuss these issues in your particular industry.
Disclaimer: this article has been written by a human, and humans are prone to mistakes. If I’ve gotten something wrong, and you can show me how with good references, I will correct my work with gratitude.
If, however, you don’t like what I’ve written because I’ve taken a dump on your pet idea, by all means contact my employer, Spitfire Research, who will be very happy to tell you to piss off and write your own article.