Why WPC decking is hard to recycle — and this is not
A wood-plastic composite board is typically 50–70% wood flour bound in a polyolefin. That wood is what gives WPC its look and its price, but it also caps the recyclability: cellulose degrades at the temperatures needed to reprocess the polymer, absorbs moisture during service life, and turns the board into a mixed organic-polymer waste that few recyclers will accept. Most end-of-life WPC therefore goes to energy recovery.
Replace the wood with a mineral-reinforced recycled polyolefin and the board stays inside one material family. Offcuts from the saw line go straight back into the hopper. At end of life, the board is a polyolefin with a known ash content — something a recycler can price, not a composite they have to guess at. That is the argument buyers are actually making when they search for recyclable decking.
Profile geometries that run today
Boards are specified by cross-section, and the geometry matters more than the marketing name. A carton-derived polyolefin extrudes on the same dies used for hollow and solid WPC profiles, with minor adjustments to the cooling tank and haul-off speed because the melt strength differs from a wood-filled compound.
- 145x21 mm solid or ribbed board — the most requested terrace profile in Europe.
- 140x25 mm and 150x25 mm — heavier commercial and public-space decking.
- Hollow chambered boards — lighter, lower material cost, same visible face.
- 25x25 mm to 50x30 mm battens and joists — substructure that will not rot.
- Cladding and fencing profiles — the same compound, different die and texture.
- Coextruded cap layer optional — a thin virgin or pigmented skin over a recycled core.
Outdoor performance: moisture, UV, slip and fire
The clearest gain is moisture. With no cellulose in the formulation there is nothing to absorb water, so boards do not swell, cup or feed fungi and the mould staining common on wood-filled decking after a couple of wet winters simply does not start. Freeze-thaw cycling is a non-event for a polyolefin.
UV needs to be engineered in, exactly as it does for WPC: a UV stabiliser package plus pigment, because unprotected polyethylene chalks. Slip resistance comes from the surface texture — brushed, grooved or embossed — not from the resin. For fire behaviour, an unfilled polyolefin board will sit around Euroclass E, so projects with reaction-to-fire requirements need a flame-retardant package; that is a formulation decision your compounder makes, and the aluminium already present does not substitute for it.
Processing notes for extruders
The pellet runs at 180–220 °C with an MFI of 2–4 g/10 min, which puts it in the same band as the polyolefin carriers used in profile extrusion. Aluminium flakes are already dispersed, so you are starting from a filled system: expect higher melt viscosity and slightly higher torque than an unfilled recycled LDPE, and a stiffer, more dimensionally stable extrudate.
Practical points: dry-blend colour and additive masterbatch as usual; keep screen packs coarse enough that the aluminium does not build pressure; and calibrate cooling for the higher density (950–1050 kg/m³) since the profile carries more mass per metre than a wood-filled board of the same section. Vicat softening at 90–100 °C means dark boards in full sun should be specified with adequate rib support, as with any polyolefin decking.
Compliance and the recycled-content story
For public tenders and large private projects, recycled content is increasingly a scored criterion rather than a nice-to-have. Because the base pellet is 100% post-consumer material recovered from post-consumer packaging and produced following UNE 53925:2026, a board's recycled-content percentage is documented at the pellet level and traceable to the waste stream — which is what an auditor asks for under CSRD/ESRS E1, EU Green Public Procurement and EcoVadis questionnaires.
The carbon argument follows the same logic. Substituting a tonne of virgin polyolefin avoids roughly 1.6 t CO₂e, so a decking range converted to recycled feedstock moves a visible line in the customer's Scope 3 category 1 inventory. We supply the batch-level documentation to support that claim rather than asking anyone to take it on trust.
Recycled PolyAl decking vs wood-filled WPC
| Base material | 100% recycled polyolefin + aluminium |
|---|---|
| Wood flour content | None |
| Water absorption | <0.5% (vs 5–12% for WPC) |
| Density | 950–1050 kg/m³ |
| Processing temperature | 180–220 °C |
| Recyclability at end of life | Reprocessable as a filled polyolefin |
| Typical profiles | 145x21, 140x25, 150x25 mm, battens |
| Standard | UNE 53925:2026, batch documentation |