Recycling's hidden microplastic menace

Recycling plastic facilities repurpose plastic into new products, but are they also releasing even more microplastics into the environment?
Tejasri Gururaj
A hand holding microplastics under a magnifying glass.
Recycling may be making the microplastic problem worse.

Sansert Sangsakawrat 

  • Microplastics have now been found just about everywhere on Earth - including inside our bodies.
  • These plastics represent a wide variety of health and environmental risks.
  • It turns out that plastic recycling may be making this problem worse.

One garbage truck of plastic is dumped into the ocean every minute. What might be even more surprising is the estimated 14 million tons (or 14 billion kilograms) of microplastics residing on the ocean floor.

Microplastics are tiny pieces of plastic, less than five millimeters in length, that have now been found contaminating almost everywhere on Earth — from bodies of water, to soils, our bodies, and even the atmosphere. They can come from a variety of sources, including large pieces of plastic that are broken down and microbeads, a type of microplastic used in cosmetic products.

These particles are harmful on their own, especially to aquatic life, as they can pass through water filtration systems undetected. They are also responsible for transporting and releasing toxic contaminants into the environment. 

Recycling's hidden microplastic menace
Microplastics can pass through water filtration systems undetected.

Since this issue has come to light, many initiatives have been taken to reduce plastic waste in general and attempt to manage the microplastics being released into the ocean. 

The United Nations Environment Programme (UNEP) launched The Honolulu Strategy through its Global Partnership on Marine Litter in 2012.

This framework includes three goals: reducing land and sea-based sources of marine debris, as well as accumulated debris, with strategies such as promoting the 5Rs (reduce, reuse, recycle, redesign, and recover) to address microplastics.

However, new research suggests that recycling, at least, may not be a solution. A new study conducted at the University of Strathclyde in Scotland, led by Masters student Erina Brown (formerly affiliated with the university) and Dr. Deonie Allen, from the university's Department of Civil and Environmental Engineering, revealed that recycling facilities actually release microplastics into the environment.

According to their research, published in the Journal of Hazardous Materials Advances, a single facility can emit up to 1.3 million kilograms (almost 3 million pounds) of microplastics yearly.

Interesting Engineering recently spoke to lead author Erina Brown about their research. 

Speaking of the motivation behind the study, she said, "There has been a huge increase in microplastic research in recent years, and we have increasing awareness of the rapidly increasing problem. This includes research into point-source pollution, such as wastewater treatment plants.

However, there seemed to be a huge gap in research into the potential for plastic recycling facilities to act as a source of microplastic pollution, with only two studies published globally, both looking at particles much larger than we looked into."

Inside a recycling facility

To understand how these microplastics end up in the environment, we have to start at the source, plastic recycling facilities. These facilities receive plastic waste from various sources and then go through a multi-step process to convert the waste into reusable materials.

Once the plastic waste is collected, it is then sorted by type, such as PET (polyethylene terephthalate) or HDPE (high-density polyethylene). Following this, the plastic waste is shredded or ground into smaller pieces. This step is necessary for the subsequent processing stages, but it is also where microplastics are generated.

Recycling's hidden microplastic menace
PET is the most commonly-used type of plastic in the world.

The shredded or ground plastic is thoroughly washed to remove impurities, such as dirt, labels, adhesives, and contaminants. Water and cleaning agents are used to clean the plastic flakes or granules. This process releases microplastics into the water.

Brown and her team began their research by collecting the water from each step in the recycling process. This allowed them to compare the microplastic content at different stages of the recycling process.

Samples were collected from the four wash water discharge flow paths within the facility.

"Due to the timeline of the facility, we took samples before any [filtration] had been installed at the facility and then compared these with samples following the installation of filtration. We then analyzed these water samples in a controlled laboratory," said Brown.

Following the washing step, the plastic waste is melted and converted into small granules or pellets. These are purchased by manufacturers to be molded into new products. But the damage has already been done. The water from the facility, containing microplastics, has been released into various sources and contaminated the environment.

Microplastics everywhere

Brown and her team analyzed the samples for microplastic content, and the findings may surprise you. They found up to 75 billion particles of microplastics per meter-cube of filtered water!

Recycling's hidden microplastic menace
The different stages in a recycling facility and the points from where Brown and her team collected the samples.

“We calculated estimates of yearly totals of up to 1,366 tonnes (approximately 1.36 million kilograms) of microplastics released into the wash water with filtration installed. This rose to 2,933 tonnes (approximately 29.3 million kilograms) in the pre-filtration samples. In two of the sample points, approximately 95% of the microplastics were under 10 micrometers and 80% under 5 micrometers,” said Brown. 

But what about areas other than water? Recent research has shown that microplastics are also being found in soil, the sky, and food. 

A study led by Janice Brahney from Utah State University found that even the most remote and protected areas of the United States, such as national parks and wilderness areas, had a significant accumulation of microplastics, which had been transported there by rains and wind. 

According to the United Nations Environment Program (UNEP), microplastic pollution in soils, sediments, and freshwater environments is estimated to be significantly higher than in marine environments. 

The use of sewage sludge as fertilizer also contributes to the distribution of microplastics in soils and on farms. Basically, they are everywhere. 

Microplastics and climate

The presence of microplastics is even thought to have an affect on the Earth's climate.

Recycling's hidden microplastic menace
The major source of microplastics in the atmosphere in the Western US is likely from roads and tire wear.

A study led by Laura E. Revell, from the University of Canterbury, found that microplastics actually have a dual effect on the environment — they can scatter sunlight, cooling the climate, and they can also absorb radiation emitted by the Earth, contributing to the greenhouse effect. 

Although the current concentration of airborne microplastics is low and their influence on global climate is thought to be minimal, a more significant impact is anticipated in the future due to projections of increasing amounts of microplastics in the atmosphere.

Apart from the climate, microplastic pollution has a direct impact on aquatic life, local ecosystems, and human health. These effects are very serious and if not handled properly can have detrimental effects on a number of ecosystems. 

“Particles under 10 micrometers have been shown to be environmentally relevant. Many organisms, from large marine birds to zooplankton, have been found to have ingested microplastics, and nanoplastics (the category of plastic particles smaller than 1 micrometer) have been found in human blood. Research back to the 1990s has shown increased cases of interstitial lung disease in workers working in factories [where they inhale] microplastics,” explained Brown.

Recycling's hidden microplastic menace
Microplastics become trapped in marine habitats.

Microplastic pollution on land has detrimental effects on sub-surface species and soil functions. It disrupts the delicate balance of ecosystems by decreasing the populations of micro-organisms that reside beneath the surface, many of which are essential for soil and plant health.

Additionally, chlorinated plastics contribute to soil and water contamination, releasing harmful chemicals that can harm surrounding ecosystems.

And now it is clear that recycling of plastics may not be the solution to avoiding this contamination. 

Tackling the problem

To tackle this problem, we need to first understand where microplastics come from. Many of them come from clothing and cosmetic products.

A single wash of a synthetic jacket can release around 1.7 grams of microplastics into the water. Microbeads — used in cosmetic products and sunscreens — also contribute significantly. 

Several countries, including the UK, Netherlands, Ireland, and Canada, have banned the use of microbeads in cosmetic products in order to tackle this issue. 

Brown and her team recommend incorporating additional filtration methods to remove smaller microplastics in water at recycling facilities. However, this poses significant challenges due to the large volumes of microplastics in the water. 

Recycling's hidden microplastic menace
Both lay respondents and experts are uncertain about the risks associated with microplastics.

"Some methods are coagulation or flocculation (designed to clump the particles together for easier removal), or others, such as the use of magnetics, can help to remove microplastics from the wash water in the recycling facilities. The issue with these methods is that the challenge is to make them economically viable or effective when scaled up to the necessary volumes," explained Brown. 

Brown also thinks that integrating microplastics into water quality regulations is necessary. 

"Though this is necessary, I do not believe it is sufficient. The real solution we actually need to implement is a massive global reduction in plastic production and consumption. Single-use plastics are slowly being reduced, but this is at an item-by-item pace."

"Every day, the world has more plastic than the day before, and this is increasing daily. We need a drastic, impactful change in our mentality towards the use of plastics within the economy and our lives, and international decisions must be made and committed to in order to do so," explained Brown.

But what about the plastic that already exists on Earth? Scientists have found some innovative solutions for that. 

Recycling's hidden microplastic menace
The various sources of microplastics, release routes, and sinks.

Scientists are now bioengineering enzymes and microorganisms that can break down plastic. In 2016, a team led by Shosuke Yoshida reported a new species of bacteria called Ideonella sakaiensis which can use PET as an energy and carbon source.

The bacteria produces enzymes that convert PET to two environmentally friendly monomers, terephthalic acid and ethylene glycol.

In another study, led by Harry P. Austin from the University of Portsmouth, scientists discuss PETase, an enzyme capable of breaking down highly crystalline PET. 

They engineered the enzyme to enhance its PET degradation capacity and found it can also degrade another plastic called polyethylene-2,5-furan dicarboxylate, opening up possibilities for recycling biobased plastics.

These findings indicate the potential for further protein engineering to improve the performance of PETase and emphasize the need for developing a better understanding of the biodegradation of synthetic polyesters.

Recycling's hidden microplastic menace
Ideonella Sakaiensis adhering to the PET with its thin flagellum and delivering PET-degrading enzymes to the plastics surface.

Moving forward

Plastics can take up to 500 years to decompose, and now we know that recycling is not a complete solution. 

Microplastics are making their way into the food chain via animals, which ingest microplastics and then pass them up the chain when they are themselves eaten. This is known as the trophic transfer of microplastics. 

Dealing with plastic waste and microplastics being released into the environment is crucial. 

"We can assume that similar facilities around the world are generating similar amounts of microplastic pollution. However, we need to expand our knowledge internationally to determine this to progress in this field, we currently have so little awareness of," said Brown. 

According to her, the answers lie within the recycling industry. She explained, "In my opinion, the waste industry, and within that the plastic recycling industry, need to be much more open in sharing knowledge industry-wide as well as to the public and policymakers. Without sharing knowledge, data, challenges, or solutions, I cannot see how the industry hopes to progress towards improving."

But looking for innovative solutions using bioengineering techniques might be our way out of it. 


The situation is alarming, but it is never too late to start working on it if we want to find a long-term solution.

Study abstract

With current plastic production and the growing problem of global plastic pollution, an increase and improvement in plastic recycling is needed. There is limited knowledge or assessment of microplastic pollution from point sources such as plastic recycling facilities globally. This pilot study investigates microplastic pollution from a mixed plastics recycling facility in the UK to advance current quantitative understanding of microplastic (MP) pollution release from a plastic recycling facility to receiving waters. Raw recycling wash water were estimate to contain microplastic counts between 5.97 x 106 – 1.12 × 108 MP m−3 (following fluorescence microscopy analysis). The microplastic pollution mitigation (filtration installed) was found to remove the majority of microplastics >5µm, with high removal efficiencies for microplastics >40µm. Microplastics <5µm were generally not removed by the filtration and subsequently discharged, with 59-1184 tonnes potentially discharged annually. It is recommended that additional filtration to remove the smaller microplastics prior to wash discharge is incorporated in the wash water management. Evidence of microplastic wash water pollution suggest it may be important to integrate microplastics into water quality regulations. Further studies should be conducted to increase knowledge of microplastic pollution from plastic recycling processes.

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