Waste Processing and Microplastics: Is Recycling Creating a New Pollution Problem?

You might also call this article: “Microplastics from Waste Processing: The Hidden Risks of Shredding and Depackaging”.

Microplastics from waste processing may well be one of the recycling industry’s least recognised pollution risks.

Waste treatment is intended to recover resources and prevent pollution. However, some mechanical processes can unintentionally convert easily captured pieces of plastic packaging into particles small enough to escape through screens, enter wastewater, become airborne or remain mixed with recycled organic material.

Shredders, grinders, mills, granulators, hammer-based depackagers and other size-reduction equipment can all fragment plastic. In plastic recycling, reducing material to flakes may be a necessary part of the process. In food-waste depackaging and organic-waste preparation, however, breaking packaging into very small particles can be actively counterproductive.

Once microplastics have been mixed into wet food pulp, compost feedstock, digestate or process water, removing them becomes technically difficult and potentially uneconomic.

This raises an important question for waste operators, equipment suppliers and environmental regulators:

Are some supposedly sustainable waste-processing systems solving one waste problem while creating another?

Key Takeaways for Microplastics from Waste Processing

Microplastics are generally defined as plastic particles smaller than 5 millimetres.
Mechanical shredding, grinding, abrasion and washing can create and release microplastic particles during waste processing.
Research has identified size reduction as an important source of microplastic generation within mechanical plastic recycling.
Microplastics may leave waste facilities in wastewater, airborne dust, process residues and products made from contaminated organic material.
Plastic entering compost or digestate can subsequently be spread onto agricultural land.
Compliance with a maximum physical-contaminant limit does not necessarily prove that the material is free from much smaller plastic particles.
Food-waste depackaging equipment should be assessed according to how much plastic it fragments, not merely how much food it recovers.
Where size reduction is unnecessary, keeping packaging pieces large and readily separable should be treated as a fundamental design objective.

What Are Microplastics?

Microplastics are commonly described as solid plastic particles smaller than 5 millimetres. The category includes particles visible to the naked eye as well as fragments and fibres too small to identify without specialist equipment.

Still smaller particles are often described as nanoplastics, although definitions and analytical size thresholds vary.

Microplastics are usually divided into two broad categories:

Primary microplastics, which are manufactured or intentionally used at a small size, such as some industrial abrasives and plastic feedstock particles.
Secondary microplastics, which are produced when larger plastic objects fragment through cutting, abrasion, weathering, ultraviolet exposure or mechanical wear.

Waste processing can generate secondary microplastics rapidly. Instead of fragmentation taking place gradually outdoors, industrial machinery can apply cutting, impact, shear and abrasion forces within seconds.

Why Small Plastic Particles Are Such a Persistent Problem

Most conventional plastics do not biodegrade in the same way as food, paper or untreated plant material.

They may become brittle and fragment into progressively smaller pieces, but this physical breakdown does not necessarily mean that the plastic has disappeared. It may instead become more widely dispersed and substantially harder to recover.

Microplastics have been detected across marine, freshwater, terrestrial and atmospheric environments. The European Commission identifies their presence in the sea, soil, food and drinking water as a growing concern for ecosystems, biodiversity and potentially human health.^[1]

Large plastic packaging can be picked, screened or trapped. Very small fragments may pass through conventional screens, travel with process water, settle into sludge or remain suspended in an organic slurry.

Once widely dispersed into soil or water, recovering these particles is rarely practicable.

How Waste Processing Can Generate Microplastics

Many waste-treatment systems depend on mechanical action. This may include:

Shredding
Grinding
Crushing
Granulation
Milling
High-speed impact
Screening and agitation
Washing and friction cleaning
Pumping through abrasive equipment

These operations can be necessary and beneficial. Plastic recycling, for example, commonly requires material to be sorted, reduced to a controlled flake size, washed and reprocessed.

The environmental problem arises when the fines, fragments and fibres created by these processes are not contained and recovered.

A 2023 study examining microplastic generation during a simulated plastic-recycling process identified the size-reduction stage, involving mechanical shredding, as the predominant source of microplastic formation.^[2]

Further research published in 2024 found that shredding plastic produced airborne microplastics and nanoplastics. The researchers also reported higher particle emissions from waste plastics than from equivalent new plastics, potentially because waste materials contained labels, adhesives and other additives.^[3]

This evidence challenges the assumption that recycling processes are inherently pollution-free simply because they recover material.

Microplastics from Plastic Recycling

Mechanical plastic recycling typically involves several stages:

Collection and sorting
Removal of unsuitable items
Shredding or granulation
Washing
Separation and drying
Melting, extrusion or pellet production

Cutting plastic into flakes increases its surface area and exposes it to repeated mechanical contact. Friction between plastic, machinery and other waste can generate fines.

Washing can then transfer small particles into the recycling plant’s wastewater.

Research on plastic-recycling facilities has indicated that microplastic losses can occur during processing, particularly through waterborne discharges. A global assessment published in 2024 concluded that mechanical recycling represents a source of microplastic discharge and estimated that releases could be significant at global scale.^[4]

This does not mean that plastic recycling should be abandoned. Recycling avoids some virgin-material consumption and can retain material within productive use.

It does mean that recycling plants should be designed and regulated as potential generators of fine plastic particles.

Suitable controls may include:

Enclosing shredders and conveyors
Local exhaust ventilation
Dust capture and filtration
Closed-loop process-water systems
Fine screening or membrane treatment
Settlement and sludge management
Cleaning methods that avoid washing plastic dust into drains
Monitoring of water and airborne emissions

One proposed process modification is to install a dedicated sieving stage between shredding and washing so that newly generated particles can be captured before entering wash water.^[5]

Airborne Microplastics and Worker Exposure

Microplastic pollution is not solely a water-management issue.

Dry shredding, handling, screening and conveying can release plastic dust and fibres into the air. Smaller particles may remain suspended, travel within buildings or escape through ventilation systems.

The 2024 shredding study found particle concentrations during plastic size reduction substantially above background levels, demonstrating that shredding can be a direct source of airborne microplastics and nanoplastics.^[3]

This creates two distinct concerns:

Environmental release: Fine particles may leave the site through doors, ventilation outlets, vehicle movements or deposited dust disturbed by wind and rain.
Occupational exposure: Workers may inhale dust generated around shredders, granulators, transfer points and cleaning operations.

The precise health effects of microplastic exposure remain under investigation. The World Health Organization has concluded that important uncertainties and research gaps remain regarding dietary and inhalation exposure to microplastics and nanoplastics.^[6]

It would therefore be inaccurate to claim that every exposure will result in illness. It would be equally unwise to assume that uncontrolled exposure is harmless while the evidence base is still developing.

A precautionary approach should include exposure assessment, effective ventilation, good housekeeping and suitable respiratory protection where engineering controls cannot adequately contain dust.

Food-Waste Depackaging Can Create an Avoidable Problem

The microplastics issue is especially important when processing packaged food waste.

The purpose of a food-waste depackager is to separate organic material from plastic, metal, card and other packaging. Unlike a plastics granulator, its purpose should not normally be to manufacture small plastic flakes.

Nevertheless, some depackaging systems rely on aggressive impact, hammering, milling or shredding to open the packages and force their contents through a screen.

This may achieve a high apparent food-recovery rate, but it can also break films, trays, labels and laminates into small particles.

The recovered food pulp may look acceptably uniform while containing plastic fragments too small to be seen during a casual visual inspection.

This creates an important procurement principle:

A depackager should not be judged solely by how much organic material passes through its screen. It should also be judged by how much packaging it breaks into particles capable of passing through that screen.

Why Screen Size Alone Is Not an Adequate Safeguard

Equipment suppliers sometimes refer to screen aperture as though it defines the maximum contaminant size within the recovered organic fraction.

It does not.

A screen can retain an intact piece of plastic larger than its apertures. It cannot retain every fragment that has already been reduced below the aperture size.

For example, a system fitted with a 10-millimetre screen may stop large packaging pieces while allowing numerous smaller fragments to enter the organic pulp.

Changing to a finer screen may reduce some contamination, but it can also:

Restrict throughput
Increase blockages
Increase energy consumption
Require more water
Increase wear
Encourage further mechanical fragmentation

The preferable approach is to avoid unnecessary plastic fragmentation at the start of the process.

Microplastics myth and reality graphic. — Although you might immediately assume that these bits of plastic build up in our stomachs, they don’t. The concern is at a much smaller scale and mostly about chemicals leaching from the plastic particles.

Microplastics in Anaerobic Digestate

Depackaged food waste is commonly processed by anaerobic digestion. During digestion, microorganisms convert biodegradable organic matter into biogas, but conventional plastic packaging is not digested.

Plastic entering the digester may therefore:

Remain suspended in the digestate
Accumulate within tanks
Settle with grit and sediment
Become entangled in pumps and mixers
Pass into separated liquid or fibre fractions
Leave the plant within digestate applied to land

Digestate can be a valuable source of plant nutrients and organic matter. However, where it contains plastic fragments, land application can disperse those contaminants over agricultural soils.

England’s anaerobic digestate resource framework places limits on physical contaminants in digestate that is to cease being waste. It states that the maximum allowed plastic concentration is a defined fraction of the total physical-contaminant limits in PAS 110.^[7]

These controls are important, but a physical-contaminant test may not capture every particle at microplastic or nanoplastic scale.

Meeting a conventional contaminant limit should therefore not be interpreted as proof that no very small plastic particles are present.

Microplastics in Compost

Plastic contamination can also enter compost through:

Plastic bags used to present food or garden waste
Packaging mixed with commercial food waste
Plastic labels, ties and plant pots
Disposable items incorrectly placed in biowaste collections
Fragments remaining after mechanical preprocessing
Products incorrectly assumed to be compostable

England’s compost resource framework specifies a maximum plastic concentration of 0.06% by mass in air-dried compost produced from waste.^[8]

Such limits provide a basic quality-control threshold, but they do not eliminate the need to prevent fragmentation.

A small mass of plastic can represent a very large number of particles when the material has been broken into fine fragments.

Once contaminated compost has been spread, the plastic may be:

Mixed into topsoil
Transported by surface runoff
Moved through soil disturbance
Carried by wind where particles become exposed
Transferred into drainage systems and watercourses

Plastic Contamination of Agricultural Land

The repeated application of contaminated compost, digestate, sewage sludge or other organic amendments creates the potential for plastics to accumulate in soil.

This route deserves particular attention because landspreading is intentional and repeated. Even low concentrations applied over large areas and across many years may create a long-term reservoir of plastic particles.

Microplastics in soil may interact with soil structure, organisms, water movement and other contaminants. Their behaviour depends on particle size, polymer, shape, surface condition and local environmental conditions.

The precise long-term consequences remain an active area of research. However, it is clear that removing dispersed plastic from cultivated soil would be exceptionally difficult.

Prevention before land application is therefore substantially more realistic than remediation afterwards.

Stormwater Runoff from Waste Sites

Plastic dust and fragments deposited on roads, yards and loading areas can be mobilised during rainfall.

Stormwater can carry these particles into:

Site drains
Settlement lagoons
Public sewers
Streams and rivers
Groundwater infiltration systems

Waste operators should not assume that conventional oil interceptors or coarse settlement systems will capture fine, buoyant or low-density plastic particles.

Good practice should include:

Keeping fragmentation operations under cover
Separating clean and potentially contaminated drainage
Using dry cleaning or vacuum recovery rather than hosing surfaces
Inspecting yards for escaped plastic fragments
Containing shredder and baler areas
Assessing whether drainage treatment captures fine plastics

Microplastics in Wastewater and Sewage

Wastewater treatment plants can remove a substantial proportion of incoming microplastics from the liquid stream, particularly through settlement and advanced treatment.

However, removal from water does not necessarily destroy the particles. Much of the captured material may be transferred into sewage sludge.

Where sludge is applied to land, this can move microplastics from an aquatic pollution pathway into a terrestrial one.

Some particles may also remain in treated effluent, particularly at smaller sizes or where treatment is less advanced.

The solution cannot therefore rely solely on wastewater treatment. Preventing plastics from entering process water is preferable to attempting to remove every fragment later.

Do Microplastics Attract Other Pollutants?

Plastic particles can interact with chemicals present in the surrounding environment. Their surfaces may adsorb hydrophobic contaminants, while the plastics themselves can contain additives such as plasticisers, pigments, stabilisers and flame retardants.

The significance of plastics as a carrier of pollutants varies according to polymer type, particle condition, chemical concentration and the wider exposure route.

It is therefore too simplistic to state that every microplastic particle becomes highly toxic. However, their ability to carry additives, microorganisms or environmental contaminants adds to the case for limiting uncontrolled releases.

Biodegradable Plastic Is Not a Universal Solution

Replacing conventional plastic with biodegradable or compostable products is often proposed as a solution.

However, these terms require care.

A biobased plastic is not necessarily biodegradable. A product certified as industrially compostable may require controlled temperature, moisture and treatment times that are not available in soil, water, home composting or anaerobic digestion.

The European Commission notes that biodegradable and compostable plastics should be used where reduction, reuse or conventional recycling are not feasible, and where the environmental benefits of the intended application can be demonstrated.^[9]

Introducing unsuitable “biodegradable” packaging into waste streams may create operational confusion and does not remove the need for correct collection, treatment and quality control.

A Better Design Principle for Food-Waste Depackaging

Where the objective is to recover food from packaging, the best environmental principle is straightforward:

Open the package, release the food and retain the packaging in the largest practicable pieces.

Maintaining larger pieces makes packaging easier to:

Screen from the organic fraction
Inspect visually
Wash if necessary
Sort for material recovery
Use as refuse-derived or solid recovered fuel where permitted
Contain during transport and storage

By contrast, pulverising the packaging can produce two contaminated outputs:

Organic pulp containing small plastic fragments
A wet reject containing lost organic material and fragmented packaging

Throughput and gross organic recovery are therefore inadequate as the sole measures of depackaging performance.

What Depackaging Equipment Buyers Should Measure

Trials should use representative waste and should assess both output streams.

Recommended performance criteria include:

Organic recovery: The proportion of available food transferred into the organic output.
Visible physical contamination: The mass of plastic, metal, glass and other contaminants in the pulp.
Fine-particle contamination: Plastic fragments below the normal visual inspection or coarse-screening range.
Organic loss: Food remaining with the rejected packaging.
Reject moisture: The amount of water and food carried out with the reject.
Packaging integrity: Whether films, trays and containers remain largely intact or are pulverised.
Water consumption: The volume required per tonne processed.
Airborne emissions: Dust generated around the machine and discharge points.
Wastewater quality: Suspended solids and plastic particles leaving wet processes.
Downstream consequences: Accumulation in pumps, tanks, screens and digestate-treatment equipment.

Results should be based on representative composite sampling rather than selected photographs or a small number of hand-picked samples.

Measures Waste Operators Can Take Now

Waste operators need not wait for a complete international testing standard before taking proportionate action.

1. Review Every Size-Reduction Stage

Identify where plastic is cut, shredded, abraded, milled or impacted. Determine whether size reduction is essential or merely conventional practice.

2. Enclose Dust-Producing Equipment

Shredders, screens, conveyors and transfer points should be enclosed where practicable and connected to suitable extraction and filtration systems.

3. Control Process Water

Operators should identify where plastic fines enter wash water and assess whether existing settlement, screening and filtration systems capture the relevant particle sizes.

4. Stop Routine Hosing of Plastic Dust

Hosing floors and machinery may transfer a visible housekeeping problem into the drainage system. Industrial vacuuming or contained dry collection may be preferable.

5. Sample Both Products and Emissions

Testing should extend beyond the saleable recycled material. Wastewater, sludge, dust and residues should also be considered.

6. Specify Low-Fragmentation Depackaging

Food-waste processing contracts should require suppliers to demonstrate that packaging is opened and separated without unnecessary grinding.

7. Improve Feedstock Quality

Source segregation and rejection of unsuitable loads remain essential. No mechanical separator can fully compensate for heavily contaminated input material.

8. Record Plastic Contamination Trends

Routine data can identify deteriorating separation performance, worn screens, damaged components or changes in incoming waste composition.

What Regulators and Industry Bodies Should Do

Microplastic control within waste processing remains less mature than controls for conventional suspended solids, litter, dust and visible physical contamination.

Regulators and standards organisations should consider:

Developing consistent sampling and analytical methods
Defining meaningful particle-size bands
Requiring assessment of airborne and waterborne releases from shredding
Revising organic-recycling standards as analytical methods improve
Establishing comparative depackaging test protocols
Including fragmentation potential within best available technique assessments
Requiring suppliers to disclose water use and fine-plastic generation
Supporting research into plastics in compost, digestate and agricultural soil

Regulation should distinguish between processes in which plastic size reduction is technically necessary and those in which it is avoidable.

For a plastic recycler, controlled shredding may be required to manufacture a usable secondary raw material. For an organic-waste depackager, pulverising the packaging may indicate poor separation design.

The Precautionary Case for Low-Fragmentation Waste Processing

Scientific knowledge about microplastics is developing rapidly. There are still uncertainties concerning exposure, measurement methods, ecological effects and human-health outcomes.

Uncertainty should not be used as a reason for making claims that the evidence cannot support. Nor should it be used as a justification for avoidable plastic fragmentation.

The essential engineering logic is already clear:

Large plastic pieces are easier to contain than small ones.
Intact packaging is easier to separate than fragmented packaging.
Plastic prevented from entering digestate is preferable to plastic measured after land application.
Dust captured at the machine is easier to manage than dust dispersed across a site.
Particles kept out of water are preferable to particles requiring advanced filtration.

Reducing avoidable fragmentation is therefore a practical application of pollution prevention at source.

Conclusion: Recycling Must Not Create an Invisible Waste Stream

Microplastics from waste processing are a genuine and increasingly evidenced concern.

Mechanical recycling, shredding, grinding and washing can release fine plastic particles into air and water. In organic-waste treatment, aggressive depackaging can introduce fragmented packaging into food pulp, compost and anaerobic digestate.

The purpose of recycling is to protect resources and reduce environmental harm. That objective is undermined when a visible plastic item is transformed into thousands or millions of particles that are harder to detect, capture and remove.

No responsible equipment-selection process should now ignore the potential for microplastic generation.

For food-waste depackaging in particular, the preferred principle should be to release the organic contents while retaining the packaging in large, clean and recoverable pieces.

The waste industry should measure separation quality, plastic fragmentation, airborne dust and wastewater losses alongside throughput and organic recovery.

Small plastic particles may be difficult to see, but that does not make them a small problem.

Frequently Asked Questions

What are microplastics?

Microplastics are generally defined as plastic particles smaller than 5 millimetres. They include fibres, flakes, films, beads and irregular fragments produced intentionally or by the breakdown of larger plastic objects.

Can waste shredders create microplastics?

Yes. Research has shown that mechanical shredding can generate both airborne and waterborne microplastic particles. The quantity produced depends on the plastic, machinery, operating conditions and emission controls.

Does plastic recycling release microplastics?

Mechanical recycling can release particles during shredding, conveying, washing and drying. Proper enclosure, dust extraction, water treatment and fine-particle recovery can reduce these releases.

Can food-waste depackaging contaminate digestate?

Yes. When packaging is fragmented into particles small enough to pass through the separator, those particles can enter the organic pulp and remain within digestate produced by anaerobic digestion.

Does anaerobic digestion destroy plastic?

Conventional anaerobic digestion does not reliably break down ordinary plastic packaging. Plastic may remain in the digestate, accumulate inside the plant or leave with liquid and fibre products.

Does meeting PAS 110 mean digestate contains no plastic?

No. PAS 110 and associated resource-framework requirements impose physical-contaminant limits, but compliance should not be interpreted as proof that every microplastic or nanoplastic particle is absent.

Is a finer depackager screen the solution?

Not by itself. A finer screen may retain more fragments, but it can reduce throughput and increase blockage, water use and energy demand. Preventing unnecessary fragmentation is generally preferable.

Are compostable plastics safe for every organic-waste process?

No. Industrially compostable plastics may require specific treatment conditions and may not break down adequately in anaerobic digesters, home composting systems, soil or natural waters.

How can waste operators reduce microplastic emissions?

Operators can reduce emissions by avoiding unnecessary size reduction, enclosing equipment, capturing dust, treating and recirculating process water, improving housekeeping and monitoring products and emissions.

What should buyers look for in a food-waste depackager?

Buyers should assess organic recovery, pulp purity, fine-plastic contamination, reject cleanliness, packaging integrity, water use, dust emissions, reliability and downstream impacts.

Sources

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[Published April 2023. Updated June 2026.]

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