Zero-waste cities: #3 Plastic

Humanity produces around 460 million tonnes of plastic every year, a figure that is forecast to triple by 2060. Just under half goes to landfill, 17% is incinerated and 15% is collected for recycling, although less than 9% is actually recycled. The remaining 22% ends up in the environment, much of it in the ocean.

These were the figures under consideration by the UN Intergovernmental Negotiating Committee (INC) last year, when it met to develop an international legally binding instrument on plastic pollution. The UN’s IPCC has driven international coordination on climate change; the INC aims to do the same for plastic. It is hoped that an agreement could be reached by 2024.

So, what can be done about plastic? Though modern plastics have existed for barely a century, they have become essential to so many aspects of our lives. Can we imagine a world without them? “Plastics are light, durable and versatile,” says Fleur Ruckley, a plastics expert and circular economy consultant at WSP until March 2023, now head of implementation at waste analytics company Topolytics. “The huge variety, and the range of things they can be made to do, has revolutionized our lives. By helping to keep food fresh, supplying clean water, cheap medical equipment and much more, plastic has played a big part extending lifespans globally.”

But, as with many a 20th-century innovation, we are now experiencing the downsides of such abundance. Plastics are traditionally derived from petrochemicals, so their upstream impacts include the carbon emissions and environmental degradation associated with fossil fuel extraction. Then there are the chemicals that are added to plastic to give it the required properties, such as colour or durability. Their production also consumes energy, materials and water, and produces pollutants and waste. The extent of all of this will vary depending on where the finished product and its components are manufactured, adds Ruckley — so plastics made in countries with low-carbon energy and strict pollution and waste disposal controls will have a lower impact than those made in places without.

The same applies downstream. Plastic is notoriously slow to degrade, so plastic waste accumulates in the environment in a way that food, timber and even metals do not. In fact, the situation is even worse because plastics are not entirely stable, says Ruckley. Chlorinated plastic in landfill releases potentially harmful chemicals into soil; in the sea, plastics are broken down by sunlight and wave action into smaller and smaller pieces that can be ingested by marine life. In water and on land, bacteria attaches to plastic and starts to break it down, which leads to the escape of harmful particles and volatile compounds. There is also growing scientific evidence that plastics pollution has started to impact directly on the global carbon cycle. Microplastic pollution is now believed to be ubiquitous in the environment, and nanoplastics have been discovered throughout the food chain, even in breast milk. We do not yet fully understand what impact this has and will have in the future on health.

“The cost of plastic pollution to fishing, agriculture, recreation, health and more is just astronomical,” says Ruckley. “It surely runs into many billions. It is well worth doing something about.”

But just as there are many plastics, there is great variation in how well they are recycled: “For example, PET drinks bottles, made from polyethylene terephthalate, are very recyclable,” says Ruckley. “The infrastructure to collect and recycle it is there, and in the UK and other western countries we do recycle most of it into new bottles or other products such as fleeces.”

On the other hand, more rigid plastics are less easy to recycle and a huge amount of plastic is bonded to other plastic or other products. To recycle, it has to be separated and consolidated, so the more it is bound up with other materials, the harder it is to deal with.

Crisp or snack packets are among the worst offenders, typically made from up to seven layers of foil and plastic joined together using an industrial adhesive, but this problem applies to a great deal of plastic waste. An item of clothing that is 100% nylon is much easier to recycle than one that also contains cotton, elastane and acrylic fibres. Similarly, furniture might be made from a range of plastics, some of which may contain persistent organic pollutants (POPS), which act as fire retardants but are poisonous in themselves. “In the UK, we have new regulations designed to stop POPS entering the recycling system,” says Ruckley. “That’s good, but unfortunately it might mean that less furniture is recycled.”

The solution, she believes, is for manufacturers to consider the downstream implications of their products at design stage: “Do we really need textiles with four different fibres? Or bottles that use three different plastics, for the bottle, the seal and the lid? Does a bottle top really need to be a different colour, and a different plastic? Could the furniture be designed so that fire-safety elements were easily removable?”

Adopting a circular economy approach would see much disposable plastic replaced by materials less harmful to the planet. A great deal of plastic packaging has already been replaced with cardboard, for example, or waxed paper could be used instead of clingfilm. If a bottle is recycled into a fleece jacket, that keeps the material in use at a higher value for a longer time. “These things are seldom straightforward though,” says Ruckley. “That fleece sheds microfibres in the wash which can end up in the sea and again, via fish, in us. I know a company that recycles recovered ocean plastic into jewellery. That’s great for raising awareness, but is it just creating another plastic product that we don’t really need? We live in a complex, messy world.” Single-use plastic items like bottles and spoons are anathema to the circular economy, which pushes us to consider more clearly how to keep products at their highest value for longer and mitigate possible downstream impact at the design stage.

There is another way of dealing with plastic: burning it. In Scandinavia, waste-to-energy (WtE) plants incinerate residual waste, including non-recyclable plastic along with other high-energy wastes such as timber and wood products. “The heat is used to generate electricity and also to warm water for local district heating systems,” says David McKinnon, a WSP circular economy consultant based in Denmark.

As well as reducing the need to burn virgin fossil fuel for power, this solves a number of problems. A wide range of mixed plastics, and plastics mixed with other things, can be burnt together. They do not go to landfill, they do not end up in the environment, and the volume of waste is vastly reduced. “It’s important to note that the Scandinavian countries do separately collect a lot of plastics, paper, cardboard and timber for recycling — generally at levels well above most other Western countries,” adds McKinnon. “Landfill is used in Denmark and Sweden almost exclusively for hazardous wastes.”

But what about air pollution? “The exhaust from these plants is well treated — scrubbed clean — so most of what you see exiting the chimney is water vapour,” he explains. “The residual slag is pretty nasty stuff though, and the waste from the scrubbing also contains high concentrations of hazardous substances.” Unpleasant though these residues are, they are at least relatively small in volume, and there is some value in concentrating them so that they can be disposed of appropriately in specialized landfill. New technologies are also putting some of these wastes to use — for example, in new types of concrete where the toxic chemicals can be fixed and rendered harmless.

Not everyone is convinced that waste-to-energy plants are the most effective solution. One factor is that the bigger the plant, the more economical it is to operate. “So if you open a large new WtE plant, you will want to justify the capex by using it at full capacity for many years,” says McKinnon. “Some argue that will undermine local efforts to reduce, separate and recycle. It doesn’t really fit the circular economy paradigm.” In order to keep its own plants running, Denmark actually imports waste from other European countries: “As Scandinavia has an overcapacity of incineration facilities, it pays to fill them with someone else’s waste. That waste will contain plastics, which help maintain its calorific value and makes it valuable to WtE facilities.”

Whether incineration provides any kind of incentive for the generation of plastic waste is debatable. But then dealing with plastic waste will clearly involve many different solutions. Some, like incineration, might be better suited to the challenges we face right now. Others, like designing out plastic where possible, may matter more in the longer term. Few solutions are perfect but, given the scale of the problem, humanity perhaps cannot afford to be too picky. As Ruckley says, we live in a messy world.

This article is the third in a four-part series exploring the transition to a circular economy. To read the rest, click the links below, or download the whole series as a PDF.

#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?
Read the story

#2

Remediation

The modern world has left a legacy of polluted land and wasted materials, but the science of remediation is developing rapidly, and helping to unlock hidden value. Could yesterday’s trash be tomorrow’s treasure?
Read the story

#4

Equity

Waste has always had a disproportionate impact on low-income communities, but social and environmental goals don’t always align neatly. How can we clean up past mistakes, and create a fairer future?
Read the story