Of the 8.7 billion tons of plastic waste produced between 1950 and 2021, only 11% has ever gone through recycling. In 2019 — the most recent year for which a breakdown is available — more than two-thirds of the 353 million tons of plastic waste produced was sent to landfill or incinerated, and 22% was mismanaged. That means it was left as uncollected litter, dumped in unregulated sites on land or in water, or burnt in the open. By 2060, rising plastic production will lead to a tripling of annual waste to more than one billion tons. Yet the future for plastic pollution doesn’t have to be on a downward trajectory. Existing technology and knowledge can correct the bulk of the plastic pollution problem.
“That was a pretty big surprise to us,” Winnie Lau, director of the Preventing Ocean Plastics project at the Pew Charitable Trusts in Washington, DC, described in Nature. “We weren’t sure if we could have such a huge impact without thinking about developing new materials or entirely new systems.”
Right now, logistics and costs, among other challenges, stand in the way of bringing in these measures to their maximum capacity. But the potential is there.
Several countries have active examples of recycling. Whether policies such as these help to cut down on future plastic use is a crucial question. Have schemes to prod people to reduce plastic waste really worked to reduce the increasing amount of global plastics discarded annually?
Germany is a good example. Today, Germany recycles 70% of all waste produced, the most in the world. Two decades ago, Germany set up a simple scheme to reduce plastic waste. When people buy drinks in a disposable plastic bottle, they pay a small extra fee and get that fee returned to them by depositing the used bottle at a return center. 98% of returned bottles are recycled, and the country prides itself on the deposit scheme, as it stabilized what might have been a sharper fall in the use of reusable bottles.
People seem to feel reassured that it is fine to buy drinks in plastic bottles that will be recycled, though, and they continue to purchase single-use plastics. So there’s little evidence that the intervention actually cuts Germany’s consumption of single-use plastics. What else can be done to lessen plastic consumption?
What are researchers doing to illuminate and solve the plastics pollution problem? Primarily, they’re:
- assessing the best policies and ways to enforce them to reduce the production, use, and disposal of plastics
- creating smart recycling schemes
- designing new kinds of plastic altogether
Assessing the Best Policies on Plastics’ Reduction
Many efforts already exist to cut down on plastic waste:
- bans or taxes on certain types of plastic, such as single-use bags and takeaway containers
- regulations around how plastic waste can move across international borders
- producer responsibility schemes so manufacturers collect and recycle their plastics-containing products or fund efforts to do so
Why haven’t these approaches worked?
A team of researchers at the Global Plastics Policy Center at the University of Portsmouth, UK conducted independent assessments of plastic waste management around the world. They determined that, in most cases, there was “virtually zero monitoring of policies.” One of the biggest difficulties in implementing policies to cut down on plastics entering the environment is a lack of data on where plastics are produced, used, and end up.
Then again, Antigua and Barbuda’s 2016 ban on selling or using plastic shopping bags points to a 15% decrease in the amount of plastic discarded in landfill in its first year. Why did it work?
- a clear implementation plan
- public support
- early stakeholder engagement
- enforcement — a $1100 fine and up to 6 months in prison
Antigua and Barbuda’s success points to assessing the performance of each policy against its own objectives, the extent to which each policy reduced plastic pollution regardless of the stated purpose of the policy, and the factors contributing to policy effectiveness.
Current Knowledge & Existing Technology Solutions
The potential of possible interventions starts by revisiting current knowledge and technologies, including producing fewer plastics, clamping down on the international export of plastic waste, replacing plastics with alternative materials such as paper, and scaling up the capacity of various recycling methods.
Mechanical recycling reacts to food and additives, which can reduce the length of the polymers and degrade the plastic’s properties. That means its ability to be processed into new materials is compromised. Such downcycling can eventually render plastics unrecyclable. But breaking down plastics with enzymes can split polymers into their building blocks, or monomers, which can then be used to build plastics with the same properties as the starting material.
This isn’t new thinking — the first reports of enzymes that could degrade plastics date back at least 3 decades.
Closed-loop recycling is the goal — nearly endless recycling. A French company called Carbios is testing a technology that it says will form the basis for the world’s first enzymatic recycling plant, which will use genetically modified enzymes to break down a common plastic called polyethylene terephthalate (PET). The goal is for enzymes to overcome some of the shortcomings of mechanical recycling. The process involves sorting and separating plastics, which are a mixture of different kinds of polymers (long molecular chains); then washing them, and finally grinding or melting them down to produce new plastics.
In addition to PET, which is used in fabrics and packaging, some of the other commonly used plastics that can be recycled in this way include polypropylene (PP), used in packaging and construction, and polyethylene (PE) — a polymer that can be manufactured at varying densities and so is found in a wide range of products, from shopping bags and folding chairs to surgical implants.
Gregg Beckham, a chemical engineer at the US National Renewable Energy Laboratory in Golden, Colorado, demonstrated that combining biological and chemical catalysts could be a powerful technique for mixed plastics. The researchers used a two-step process, including a metal catalyst and an engineered soil bacterium, to degrade a blend of plastics — PET, high-density polyethylene (HDPE), a plastic commonly used in shampoo bottles and milk cartons, and polystyrene, which is used to make styrofoam — into chemicals that could be used to make new polymers.
Another technique sometimes referred to as chemical recycling is pyrolysis, in which mixed plastics are heated to extremely high temperatures in the absence of oxygen until they break down into components that can be used as fuel or for building new polymers. But this labelling is controversial. Critics question whether it can really be considered recycling — because it is often used to generate fuel — and have argued that it is an energy-intensive process that is little better than incineration. Despite these critiques, many large chemical companies are in the process of building pyrolysis plants around the world.
Existing Technologies, Adapted to Reduce Plastics Tomorrow
Could the ideal plastic replacement have a life cycle much like that of paper? It would be minimally modified from the source material, simple to recycle, and pose minimal potential for harm if it leaks into the environment.
Jeremy Luterbacher, a biochemical engineer at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, reported a way to use chemicals known as aldehydes to turn inedible biological material, such as wood chips and the cobs of maize (corn), into a biodegradable polyester, called dimethylglyoxylate xylose, that he thinks could be this replacement material. Although the production process is currently proof of concept, it should be possible to make this polyester simply and in large amounts, Luterbacher says. Work remains to bring this approach to market. For instance, if dimethylglyoxylate xylose is to be used in food packaging, researchers will need to be sure that, as it degrades, any molecules produced won’t be harmful to health or have any other unintended effects, such as leaving a bad taste.
Currently, the two biggest categories of bioplastics, polyhydroxyalkanoates (PHAs) and polylactic acid (PLAs), are both bio-based and biodegradable; they are used in applications including food packaging, cutlery and textiles. Firms are investing billions of dollars into making bioplastics. But they comprise only an estimated 1% of the more than 400 million tons of plastics produced per year.
“The plastics pollution crisis is literally visible, and it’s hard not to be heartbroken when you see it in the natural environment, especially,” Beckham from the US National Renewable Energy Laboratory admits. “I do think that humankind has recognized this problem, and I am hopeful that we can solve this. But it will take monumental amounts of work and time.”
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