Zero-waste cities: #1 The circular economy

By 2050, global cities could produce 3.88 billion tonnes of waste every single year — unless we do something about it. Can the circular economy save us from drowning in our own wastefulness?

June 2023

Words by Tony Whitehead

“We used to talk about the three Rs: reduce, reuse, recycle. There are now at least nine, but they do give a fuller picture of what the circular economy is all about”

Valentina Petrone, WSP

The world’s village dumps, or middens, have proved a rich resource for archaeologists. Here, the life of past societies — their diet, fashion, technology, even their triumphs and disasters — can be revealed by analysis of what was discarded and when.

The broad conclusion future historians might draw from examining 21st-century landfills will surely be that we were an extraordinarily wasteful society. They may well ponder how an era that could produce such a dazzling array of substances, and deploy them at vast scale in an astonishing range of materials and things, could lack the will or ability to use them more efficiently. Was it, they may wonder, an inability to manage the complexity they had created that led eventually to their downfall?

We can hope for better, but our trajectory is not encouraging. The World Bank estimates that global cities produced 2.4 billion tonnes of waste in 2020, and that this will increase by 73% to 3.88 billion tonnes by 2050. In cities in the Global South, quantities are expected to triple. These figures hint at the scale of the problem, but they tell us little about its characteristics or the potential solutions. The pie charts of waste can be drawn in numerous forms, but classically feature at least five main segments: organic, plastic, electronic or e-waste, textiles, and rubble and soil from construction and demolition. Added to this can be numerous specifics such as paper, aluminium or glass, though sections naturally blur and overlap. Each of these waste types presents its own unique set of problems. 

In developed nations, typically around one-third of waste by weight comes from demolition. This is heavy and bulky, but causes relatively few problems once in landfill because it typically comprises mainly inert mineral-based substances, such as brick, stone and glass. These derive from the ground and are put back in changed but similar form. The problem with this type of waste usually lies upstream, in the vast amounts of material and energy that were expended in its original manufacture.

For other kinds of waste, the problems also appear downstream. When organic household waste is sent to landfill, it produces large amounts of methane, a greenhouse gas at least 25 times more potent than CO2. Then there’s plastic — light, but very slow to decompose. An estimated 14 million tonnes enters global rivers and oceans every year, where it leaches pollutants and breaks down into tiny pieces that enter the food chain. Other materials we discard can produce poisonous leachate that affects soil, water and ecosystems.

Waste may be almost unimaginably diverse, but there is one approach that could potentially mitigate every problem caused by almost any imaginable waste. It’s called the circular economy.

WSP is developing a circular economy strategy and a waste management plan for the 44.6ha Arden precinct masterplan in Melbourne, Australia, in line with the city’s target of net-zero carbon emissions by 2040

In principle, this is a simple enough concept. Instead of a linear process involving resource extraction, manufacture, use and disposal, things are instead reused or recycled repeatedly, to maximize the lifespan of materials almost indefinitely. This could apply to anything from plastic bags to clothes to entire buildings.

In practice, however, there is a lot of confusion about what exactly a circular economy would look like. “People think it’s just another way of recycling,” says Valentina Petrone, leader of WSP’s circular economy practice in Australia and New Zealand. “We used to talk about the three Rs: reduce, reuse, recycle. There are now at least nine, but they do give a fuller picture of what the circular economy is all about.”

As part of the Elephant & Castle town centre regeneration project in London, WSP’s structural engineers developed a digital tool that can rapidly match a whole building design to an inventory of available components. This will allow 26% of the new steel across the site to replaced with reclaimed material. Visualization Delancey
Visualization Delancey
Model WSP

In fact, a recent study by academics at Utrecht University in the Netherlands found 114 different definitions of the circular economy. But most contemporary sources agree with Petrone that “refuse, rethink, reduce, reuse, repair, refurbish, remanufacture, repurpose, recycle, recover” has it mainly covered. “It’s not just about dealing with waste better by diverting it from landfill. It starts with reducing waste generation by not making stuff in the first place, and then keeping materials you do have in use at the highest value for as long as possible.”

At the highest value for as long as possible is central to the circular economy. For example, many countries now require demolition waste to be crushed so that the rubble can be used as backfill in new construction projects. “This is better than dumping it straight into landfill,” she says, “but rubble is a low value commodity. Far better to have repurposed the higher-value building rather than demolish it.”

Or take glass. Significant resources go into collecting glass bottles, though most glass is not recycled into new containers, but crushed and used for road-base or similar. “Better road-base than landfill, but it’s a low value, sub-optimal outcome,” says Petrone. “Recycling as glass is slightly better. You save some carbon, and reduce the call on a higher-value material resource — the high-grade sand from which glass is made. Best though, would be to reuse the higher-value bottle via a deposit-and-return scheme.”

Reusing a product at its highest value avoids the energy use, carbon emissions, resource consumption and associated habitat destruction associated with producing new things, so the benefits to the environment are manifold. According to the UN’s Global Resources Outlook, the extraction and processing of natural resources is responsible for more than 90% of biodiversity loss and water stress, and approximately half of global carbon emissions. Meanwhile, research from the Ellen MacArthur Foundation found that decarbonizing energy supplies, buildings and transport will only address 55% of global emissions: the remaining 45% comes from producing things such as cars, clothes, food and the everyday products that usually end up as waste. Circular economy models offer a pathway to addressing all of these impacts and achieving collective climate goals.

So, what’s holding us back? One challenge is that the circular economy is such an all-encompassing concept that it can be hard to know where to start. “After all, where do you begin with a circle?” asks Eszter Csicsai, a project director in WSP’s US circular economy practice. “Even before going into a pilot, ask yourself: what’s your goal? Do you want to reduce upstream emissions, reduce physical waste, generate cost savings, increase revenue, or achieve more equitable engagement with customers and suppliers?” Every company’s approach will be different and multifaceted, she adds. Even those that don’t make physical products still produce waste at some point in their value chains and can benefit from a circular economy lens.

The next step is to measure. “You can’t manage what you don’t measure,” says Csicsai. “So, you need data on all of your assets. What materials do you have circulating, what comes in, what goes out, and who engages with all these things along the global value chain?”

This is an approach that can work at a company, city or national scale, says James Martin, principal circular economy consultant at WSP, based in the UK. He was involved in putting together London’s Circular Economy Route Map. This began by setting boundaries in terms of the sectors to focus on — in this case, food, textiles, plastics, electricals and the built environment — and then carrying out material flow analysis.

“It is generally possible to identify what comes in and where it goes, and then we identify what was lost to system leakages or landfill, and why,” he explains. “Then it is a question of identifying the stakeholders who can influence this. For example, when looking at wastes, bringing together those that generate or manage wastes with those who can valorize it into wholly new products.”

"You need data on all of your assets. What materials do you have circulating, what comes in, what goes out, and who engages with all these things along the global value chain?"

Eszter Csicsai, WSP

Again, this works at many levels and across multiple sectors. For example, Toast is a London company using waste bread to brew beer, while the London Centre for Sustainable Fashion seeks to encourage textile reuse and the design of longer-lasting “slower” fashion.

There is often a clear economic logic to making use of waste: “Think of it less as material to be discarded or managed, and instead as a resource — one that can generate income, improve your sustainability credentials and potentially create a competitive edge in your market,” says Martin.

What may be harder is to encourage companies to make less stuff in the first place. “Fast fashion is a good example,” says Csicsai. “Brands want you to buy the next new style and get rid of the old one. Often there seems little natural synergy between the circular economy and consumerism — the clue is in the name. So a key principle of the circular economy is to try to decouple virgin material extraction from revenue growth.” One way is to change how the consumer views the product: “For example, there is a lot of grass roots activism turning the tide against fast fashion.”

According to the Ellen MacArthur Foundation, 45% of global carbon emissions come from producing things such as cars, clothes, food and consumer products. Photo

Companies will benefit from a better understanding of their upstream supply chains, and of what happens to their products downstream, adds Csicsai. “If you have that visibility, you can introduce efficiencies in your manufacturing by wasting less and recirculating materials. Then, if you know more about what happens to your product after you have sold it, you might be able to identify opportunities for take back, refurbishment, reuse or resale.” Within the built environment, for example, digital product passports and building information modelling are providing greater transparency. “If you know exactly what materials go into a building, you have a better chance of salvaging and reusing parts of it in the future,” she points out.

"Think of it less as material to be discarded or managed, and instead as a resource — one that can generate income, improve your sustainability credentials and potentially create a competitive edge in your market"

James Martin, WSP

Tracking materials and products throughout their lives is far from easy. Right now, no industry has full value chain traceability, although there is progress towards it. The Product Stewardship Institute has been coordinating action on extended producer responsibility (EPR) legislation throughout the US for over two decades, and the European Union is implementing legislation in this area as well. In the EU, batteries, electronics and packaging are covered by statutory EPR, and most countries have implemented schemes for tyres and end-of-life vehicles.

Government policy is already becoming a key driver in creating economies that are more circular. When you buy an electrical household appliance in France, for example, there is usually a small part of the price labelled “éco-participation”, a fee used to fund collection and recycling of the item when it is no longer used. The money goes to non-profit organizations responsible for recycling and the amount paid depends on the cost of recycling each type of equipment. A small gadget might attract a premium of a few cents, while for larger, more complex items like fridges there could be €30 added to the cost.

WSP helped to carry out a condition assessment of three apartment buildings in the Danish cities of Copenhagen, Odense and Horsens, built 30 years ago from concrete, brick, slate and wood recovered from demolition waste. They found that the durability and strength of the recycled components was comparable to virgin materials, and that there had been no increase in maintenance costs

From a circular economy point of view, recycling schemes have a place, but the real wins are in disassembling and reusing materials before end of life, says Rowan Latham, senior waste consultant with WSP in New Zealand. The New Zealand government has identified six priority products for which it intends to develop producer responsibility: plastic packaging, tyres, electronic waste including large batteries, agrichemicals and their containers, refrigerants, and farm plastics. “This will usually involve an advance disposal fee on the price of the product that will fund its reclamation by third parties,” he explains. “But there’s usually more potential in supplier-based solutions. If a manufacturer takes back its own products it can fine-tune a disassembly line, perhaps build a specialist robot or system to deconstruct the product — something that would not normally make economic sense for a general third-party recovery firm. Manufacturers are then incentivized to design their products to make them easy to disassemble or repair.”

In France this thinking has already resulted in legislation which, since 2021, has required manufacturers of a number of electrical appliances to display a repairability index on products to help consumers understand if they are repairable, difficult to repair or not repairable at all. It plans to expand the regulations, aiming to reduce e-waste by achieving a 60% repair rate of electrical and electronic products by 2026.

Another way of promoting stewardship is not to buy or sell a product at all, but to hire it. “Take office furniture as an example,” says Petrone. “If you hire it, as well as benefiting from capex savings, the furniture user is not responsible for its maintenance or disposal — and as landfill charges rise, as they have here in Australia, so the potential savings grow. And unlike a seller, a lessor has every incentive to make furniture that lasts longer and which is easy to repair and refurbish.”

Zero-waste cities

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This is classic circular economy thinking — the materials in the furniture stay in use at a high value for as long as possible. “But why stop with furniture?” asks Petrone. “Even if you own a building, you might find benefits from leasing building elements such as elevators, lighting, or even the facade.”

As a business model, this is far from new. Aircraft jet engines are almost always leased rather than owned. But as increasing global regulation causes waste disposal costs to rise, the advantages of leasing begin to look more widely applicable. Belgian-based MUD jeans, for example, leases denim jeans for around €10 a month — roughly cost neutral for those who change their designer jeans once a year. Take-backs are reused or recycled, with new jeans currently comprising 40% recycled cotton.

It is surely grounds for optimism that there are so many ways to embrace the circular economy. But how to assess which are right for you, and which might benefit society and the environment the most? To a degree, almost any sustainability indicator — from LEED buildings assessments to organic food certification — will tend to reward circular economics. In addition, life cycle assessment (LCA) is a useful tool for understanding the various impacts a product generates, from manufacturing to end of life. And, as Csicsai points out, assessing the effects of circularity on a company’s carbon footprint may soon be easier, thanks to increased understanding and reporting of scope 3 carbon emissions (that is, indirect emissions across a global value chain).

"If a manufacturer takes back its own products it can fine-tune a disassembly line, perhaps build a specialist robot or system to deconstruct them"

Rowan Latham, WSP

But though there are many synergies, the circular economy is about more than carbon accounting, so all-embracing circular economy-specific indicators are now beginning to emerge. “For example, you could use Circulytics, or Circular Transition Indicators,” says Csicsai. In fact, there is currently something of a boom in assessment systems and frameworks, although the market is still at an early stage. “There is a need for more consistency among circularity assessments, and they need better alignment with other sustainability reporting frameworks. More consistent metrics would drive better uptake of circular initiatives.”

Also needed, says Csicsai, is more and better infrastructure to support the circular economy — such as networks connecting local resource collection, reuse and recycling hubs. “Progress on this will benefit from public and private cooperation. Government might provide appropriate locations and incentivize material recirculation through regulation. Meanwhile, industries can pool resources to innovate on shared challenges and manage materials more efficiently.”

Will the circular economy save the world? As with carbon reduction targets, there will inevitably be a wide disparity in the extent to which mature and emerging economies can engage with the idea. Though reducing waste can be economically beneficial, it requires time, focus and investment — commodities more plentiful in the Global North. The Global South has also incurred a disproportionate share of the environmental and economic burden generated by our current linear economy, while benefiting far less than the Global North — so the circular transition could be a kick-starter to building more cross-regional equity and bringing a wider array of stakeholders to the table.

As an idea though, the circular economy is rapidly gaining traction. Whether at company, city, or national level, there is a growing recognition that resources are finite, waste is costly, and to deposit ever greater quantities of stuff in the ground is unsustainable.



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