Two bio-based foam materials are increasingly mentioned in the same breath as sustainable EPS alternatives: mycelium foam (made from fungal root networks) and sargassum foam (made from ocean-harvested seaweed). Both are genuinely renewable. Both are being piloted by packaging engineers across Europe and the US. But they are not interchangeable — and choosing the wrong one for your application can cost significant time and money.
This article provides a direct, honest comparison based on what is actually known and measurable today.
What Each Material Is
Made by growing fungal mycelium (root networks) around an agricultural substrate — usually hemp or corn stalks. The mycelium binds the substrate into a solid form, which is then heat-treated to stop growth and dried.
Pioneered by Ecovative Design (US). Several European producers now in development stage.
Made by processing raw sargassum seaweed biomass through a proprietary conversion process — producing foam slabs with tunable density. No agricultural land required. Ocean biomass sourced globally.
SargasFoam operates the MK01 pilot production unit in Akmene, Lithuania.
Direct Comparison
| Criterion | Mycelium foam | Sargassum foam |
|---|---|---|
| Surface finish | Variable — can achieve smooth white, but batch consistency is a known challenge | Smooth white surface achievable; consistency under active development |
| Biobased content | High — typically 80–100% biobased | ≥85% biobased content (EN 16640 certification in progress) |
| PPWR compliance | Yes — bio-based, recyclable or compostable | Yes — bio-based content documented |
| Density range | Typically 40–100 kg/m³ — denser than EPS | 18–28 kg/m³ — comparable to standard EPS grades |
| Compression performance | Good — suitable for protective packaging | In characterisation — data available on request |
| Commercial scale EU | Limited — few suppliers at meaningful volume | Pilot scale — MK01 facility in Lithuania |
| Custom geometry | Yes — moulded to shape during growth cycle | Yes — foam slabs cut or moulded to spec |
| Lead time (sample) | 4–12 weeks depending on supplier | Available now via sample-order.php |
| Best application | Premium electronics, luxury rigid inserts | Cosmetics inserts, beauty packaging, soft-touch applications |
Where Mycelium Has the Edge
Mycelium foam is grown to shape — the mould defines the geometry. This means no cutting waste and a precise fit for complex 3D geometries. It also tends to perform well in compression tests for heavier, denser products. For rigid protective inserts around electronics or premium spirits bottles, mycelium is a serious candidate.
It has also attracted significant investment and press, which means procurement teams are more familiar with it. That familiarity can matter in internal approval processes.
Where Sargassum Foam Has the Edge
The key advantage of sargassum foam is density range. At 18–28 kg/m³, it sits in the same range as standard EPS grades — meaning it behaves similarly in applications where lightweight, soft-touch cushioning is required. This makes it a more direct functional substitute for cosmetics inserts and gift packaging.
Sargassum also requires no agricultural land and no controlled growing environment. The feedstock is ocean biomass — available globally at scale — which removes the substrate sourcing bottleneck that mycelium producers manage. And unlike mycelium, which requires a growing cycle of days to weeks per batch, foam slab production can in principle be continuous.
The Honest Answer
For cosmetics inserts and soft-touch beauty packaging: sargassum foam is a stronger candidate — the density range and surface finish align with what these applications need. For heavier protective inserts with complex geometry: mycelium is worth evaluating seriously. In both cases, there is no substitute for testing physical samples against your actual product and packaging spec.
Both materials are at relatively early stages of commercial availability. Neither should be selected based on marketing materials alone. Request samples, run your own compression and dimensional tests, and make the decision on data.
Request SargasFoam samples
Physical foam grade samples — standard, high-density, low-density. €50 per sample. Shipped EU, US, and worldwide.
Order sample kit →