LDPE recycling, explained end to end

Is LDPE recyclable? The honest answer

Technically, yes, without qualification. LDPE is a thermoplastic: heat it and it flows, cool it and it sets, and that cycle can be repeated many times before chain scission degrades mechanical properties enough to matter. Recyclers routinely blend recycled LDPE back into new products at 30–100%.

Practically, the constraint is the feedstock. A tonne of LDPE film occupies an enormous volume, picks up food residue, ink and adhesive, and is frequently laminated to other polymers or to aluminium. Sorting plants built around rigid containers struggle with it, which is why household film often ends up in refuse-derived fuel rather than in a pelletiser. When the stream is controlled — industrial stretch film, back-of-store film, or carton reject fractions — recycling rates and quality are both far higher.

The mechanical recycling process, step by step

Every mechanical LDPE line follows broadly the same sequence, with the number of washing and filtration stages varying by input quality.

• Collection and baling — separate industrial film, carton residues and kerbside plastics.
• Sorting — NIR spectroscopy separates polyethylene from PP, PET and PVC; optical sorting handles colour.
• Size reduction — shredding and granulation to a consistent flake.
• Washing — friction washing plus hot caustic wash to remove food residue, labels and adhesives.
• Separation — sink-float or hydrocyclone removes denser contaminants; polyolefins float, PET and aluminium sink.
• Drying — mechanical then thermal drying below the softening point.
• Extrusion and filtration — melt filtration removes remaining solids, then degassing removes volatiles.
• Pelletising — strand or underwater cut into a homogeneous pellet, then batch-tested for MFI, density and ash.

What recycled LDPE becomes

Film-to-film is the highest-value route but demands the cleanest input: bin liners, agricultural film, shrink hoods and construction sheeting. Below that sit rigid and semi-rigid applications, which tolerate more variability and are where most post-consumer LDPE ends up: pallets, crates, profiles, decking, cable ducting, urban furniture and drainage components.

A third route is compounding. Recycled LDPE is used as a carrier or toughening phase in filled compounds, blended with mineral filler, HDPE or PP to hit a target stiffness and price. Buyers here care more about consistent MFI than about pristine colour.

Why carton-derived LDPE is a different quality tier

Beverage cartons are roughly 75% paperboard, 20% polyethylene and 5% aluminium. Paper mills pulp them to recover the fibre, and what leaves the mill is a polyethylene-aluminium fraction — PolyAl — that never went through a household mixed-plastics sorting line. The polymer is predominantly LDPE from the laminate, with smaller shares of HDPE and PP from caps and closures.

That matters for quality. The stream is defined by a single, standardised product design rather than by whatever consumers put in a bag, so composition is stable batch to batch. Historically this fraction was incinerated for energy; washed and pelletised, it becomes a recycled polyolefin with predictable MFI and a useful stiffness bump from the dispersed aluminium.

Regulation is pulling demand forward

The EU Packaging and Packaging Waste Regulation sets binding recycled-content targets for plastic packaging, and CSRD/ESRS E1 reporting makes purchased materials a visible line in a company's Scope 3 inventory. Both push buyers from voluntary recycled content toward documented, certified recycled content with traceability.

The practical consequence for specifiers: it is no longer enough to buy a recycled pellet. You need a certificate of analysis, a stated recycled-content percentage and origin traceability that survives an auditor's questions.