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Bentofix® Green Biodegradable* geosynthetic clay liner

Naue Bentofix® Green is a biodegradable* geosynthetic clay liner for ecological waterproofing for ponds, embankments and nature reserves.

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  • Close-up of a Bentofix® Green bentonite mat (geosynthetic clay liner) showing the geotextile and bentonite layers from the top.
  • Close-up of a Bentofix® Green bentonite mat (geosynthetic clay liner) showing the geotextile and bentonite layers from the bottom.
  • Construction workers use a spreader bar and unroll a large Bentofix® Green liner into an excavated earth basin beside a grassy field.
  • Riverbank construction site with Bentofix® Green and a pile of gravel beside a river, a bridge in the background, and mountains under a clear blue sky.
  • Bentofix® Green is a biodegradable* geosynthetic clay liner (GCL): sodium bentonite between compostable geotextiles that degrade, leaving the mineral sealing layer.
  • On hydration the bentonite swells into a hydraulic barrier; after the carrier layers degrade, no synthetic substances remain in the environment.
  • 6.81 kg CO₂-eq/m² (EPD verified); biodegradable* outer layers TÜV Austria certified (OK compost & biodegradable); Seedling (EN 13432).
  • CE (EN 13491), BBA-HAPAS (no. 05/4256), TÜV Austria biodegradability, Seedling (EN 13432), ISO 9001, EPD - full list in technical data.

Bentofix® Green is a biodegradable* geosynthetic clay liner for ecological waterproofing and containment. It combines sodium bentonite powder with compostable nonwoven textile layers. When hydrated, the bentonite swells and forms a reliable hydraulic barrier. The outer biodegradable* layers degrade after installation. What remains is the sealing mineral core.

In sensitive areas such as nature reserves, certain regions prohibit the use of synthetic materials in permanent sealing systems. Conventional GCLs and geomembranes are not permitted. The only traditional alternative is thick compacted clay: 400 mm of selected fill, excavated and compacted at significant cost and environmental impact. Bentofix® Green solves this. It delivers equivalent sealing performance in a 10 mm biodegradable* composite. No synthetic materials remain after the nonwoven layers degrade*.

Bentofix® Green replaces compacted clay layers up to 400 mm thick. Excavation volumes fall. No borrow pit is required. Installation is fast: panels up to 5.0 m wide are deployed directly from the roll. The biodegradable* nonwoven components are certified by TUV Austria. CO₂ footprint: 6.81 kg CO₂-eq/m² (EPD verified). Naue GreenLine confirms the products meet EN 13432 compostability standards.

Bentofix® Green biodegradable* geosynthetic clay liner functions:

  • Barrier

    Barrier

    Sodium bentonite swells on hydration. Forms a hydraulic barrier at k approx. 1.0 x 10⁻¹¹ m/s.

  • Separation

    Separation

    Biodegradable* nonwoven layers separate the bentonite core from subgrade and cover materials during installation and the swelling phase. After degradation, bentonite retains its sealing function.

Bentofix® Green biodegradable* geosynthetic clay liner advantages: ecological sealing and technical performance

Bentofix® Green delivers certified sealing performance with fully biodegradable* outer components. Four advantages make it the preferred solution for ecologically sensitive sealing applications.

  • Biodegradable

    Natural and compostable

    Outer nonwoven layers are certified biodegradable* by TUV Austria (OK compost INDUSTRIAL, HOME, SOIL, WATER, MARINE). No synthetic substances released during installation, operation or end of life.

  • Safety

    Mineral sealing core remains

    After biodegradation* of outer layers, the sodium bentonite sealing layer retains full hydraulic barrier function at k approx. 1.0 x 10⁻¹¹ m/s. Settlement-resistant mineral waterproofing without ongoing synthetic material presence.

  • Reduced thickness

    Only 10 mm installed thickness

    Replaces compacted clay liners 400 mm thick. Reduces excavation volume, eliminates borrow pit logistics and avoids heavy machinery on ecologically sensitive ground.

  • Roll

    Wide rolls, fast installation

    5.0 m wide rolls, 30 cm colour-coded overlap guide imprinted with non-toxic ink, all-direction self-sealing overlaps. Up to 5,000 m² per day installed.

Application areas

Typical applications:

  • Long-term bank and base sealing of ponds, lakes and ornamental water features
  • Embankment sealing of dams, dykes and stormwater retention basins
  • Sealing of water bodies in nature reserves
  • Colmation mat installation for initial sealing of watercourses and canal beds

Bentofix® Green is the specified biodegradable* geosynthetic clay liner for pond and embankment sealing in sensitive environments. The compostable nonwoven outer layers degrade after installation. The sodium bentonite sealing core provides hydraulic conductivity at k approx. 1.0 x 10⁻¹¹ m/s throughout the design life. Wide rolls of 5.0 m width allow rapid coverage of large water surface areas with minimal seaming.

Advantages in ecological pond and embankment sealing:

  • No synthetic substances released: TUV Austria certified degradation in soil, freshwater and marine environments
  • k approx. 1.0 x 10⁻¹¹ m/s: equivalent sealing to 40 cm compacted clay, at 10 mm installed thickness
  • Up to 5,000 m² per day installed: less machinery, less disturbance to sensitive ecological sites
Construction workers use a spreader bar and unroll a large geosynthetic clay liner into an excavated earth basin beside a grassy field.

To the application:

Hydraulic engineeringGroundwater protection

Typical applications:

  • Historic moat rehabilitation with root-prone reed vegetation
  • Sealing of ditches and trenches to prevent subsoil water ingress
  • Initial colmation sealing of riverbeds and canal banks
  • Wetland and habitat restoration projects requiring no permanent components

Advantages in watercourse and habitat rehabilitation:

  • Colmation acceleration: bentonite swelling provides immediate initial sealing on water contact
Riverbank construction site with geosynthetic clay liner and a pile of gravel beside a river, a bridge in the background, and mountains under a clear blue sky.

To the application:

Hydraulic engineering

Technical properties

PropertyUnitSecutex® Green 30G1 GRK 2Secutex® Green 120G1 GRK 5
Nonwoven cover layer – Secutex® Green
Product type—Single-layer needle-punched staple fibre nonwovenSingle-layer needle-punched staple fibre nonwoven
Function—Protection, separation, filtrationProtection, separation, filtration
Raw material—Renewable, biodegradableRenewable, biodegradable
Mass per unit area (nominal / minimum)g/m²300 (≥ 270)1,200 (≥ 1,080)
Thickness (nominal / minimum)mm3.0 (≥ 2.7)7.0 (≥ 6.3)
Static puncture resistance (CBR)N≥ 1,000≥ 5,000
Characteristic opening size O₉₀µm7045
German geotextile robustness class (FGSV M Geok E)—GRK 2, fulfilledGRK 5, fulfilled
Detector tested—YesYes
Certified biodegradability
TÜV Austria certificates—OK compost INDUSTRIAL, OK compost HOME, OK biodegradable SOIL, OK biodegradable WATER, OK biodegradable MARINEOK compost INDUSTRIAL, OK compost HOME, OK biodegradable SOIL, OK biodegradable WATER, OK biodegradable MARINE
Seedling certificate—Acc. to EN 13432Acc. to EN 13432
Hydraulic barrier (bentonite core, identical to Bentofix® BFG 5000)
Bentonite type—Sodium bentonite powderSodium bentonite powder
Bentonite grain sizemm≤ 0.2≤ 0.2
Mass per unit area (at ≤ 15 % moisture content)g/m²5,0005,000
Swell indexml/2 g≥ 24≥ 24
Fluid lossml/2 g≤ 18≤ 18
Moisture content%1010
Permeability k₁₀m/s1.0 · 10⁻¹¹1.0 · 10⁻¹¹
Permittivity ψ₁₀1/s1.5 · 10⁻⁹1.5 · 10⁻⁹
Index flux q₁₀(m³/m²)/s2.2 · 10⁻⁹2.2 · 10⁻⁹
Close-up of a stream restoration project showing a partially covered Bentofix® Green geosynthetic clay liner (GCL) installed along the bank. The biodegradable GCL is integrated into the natural environment with soil, rocks and emerging wetland vegetation.
Close-up of a stream restoration project showing a partially covered Bentofix® Green geosynthetic clay liner (GCL) installed along the bank. The biodegradable GCL is integrated into the natural environment with soil, rocks and emerging wetland vegetation.
Bentofix® Green geosynthetic clay liner (GCL) installed as part of a stream restoration project. The biodegradable* outer layers support ecological integration, while the sodium bentonite core provides long-term hydraulic sealing for environmentally sensitive applications.
Bentofix® Green geosynthetic clay liner (GCL) installed as part of a stream restoration project. The biodegradable* outer layers support ecological integration, while the sodium bentonite core provides long-term hydraulic sealing for environmentally sensitive applications.

Biodegradable* GCL vs CCL vs standard GCL: why Bentofix® Green changes ecological sealing

Engineers specifying sealing systems for nature reserves, pond liners and ecological restoration projects face a genuine dilemma. Conventional geomembranes and standard GCLs deliver reliable hydraulic performance. In regions where regional or national authorities prohibit certain components in sensitive environments, the only established alternative has been compacted clay: thick, heavy, machine-intensive and expensive.

Bentofix® Green resolves this conflict without sacrificing technical performance. The hydraulic barrier is identical to standard Bentofix: sodium bentonite powder at 5,000 g/m² (BFG 5000), achieving k approx.1.0 x 10⁻¹¹ m/s (EN 16416 / ASTM D5887). This is two orders of magnitude better than a 400 mm compacted clay liner at k = 1 x 10⁻⁹ m/s.

The Bentofix® Green outer layers are different. Carrier and top layer are manufactured from certified biodegradable* nonwoven materials. TUV Austria independently certifies five degradation pathways: industrial composting, home composting, soil, freshwater and marine environments. The Seedling logo confirms conformity with EN 13432. Once the nonwoven components degrade, the bentonite sealing layer continues to function. Swelling sodium bentonite is the sealing mechanism: no polymer is required to maintain hydraulic performance.

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Bentofix® Green biodegradable* GCL projects: ecological sealing case studies

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Frequently asked questions

Bentofix® Green is a biodegradable* geosynthetic clay liner (GCL) for ecological waterproofing and containment. It uses compostable nonwoven textile layers around a sodium bentonite sealing core. It is used for pond sealing, embankment sealing, moat rehabilitation and applications in nature reserves where synthetic substances are prohibited.

Bentofix® Green uses compostable and biodegradable* nonwoven outer layers certified by TUV Austria. The sodium bentonite sealing core is the same. Standard Bentofix grades use conventional polypropylene (PP) nonwovens.

No. The hydraulic sealing function of Bentofix® Green is provided by the sodium bentonite core, not the nonwoven layers. After degradation* of the outer components, the bentonite retains its gel-like sealing behaviour at k approx. 1.0 x 10⁻¹¹ m/s. The nonwoven layers protect the core during installation and the initial swelling phase only.

TUV Austria certifies five biodegradation pathways: OK compost INDUSTRIAL, OK compost HOME, OK biodegradable SOIL, OK biodegradable WATER and OK biodegradable MARINE. The Seedling logo confirms conformity with EN 13432. CE marking (EN 13491) confirms GCL hydraulic performance. ISO 9001 covers quality management.

Yes. Naue’s geosynthetics engineers provide project-specific system specification, slope stability analysis and installation planning at no charge. Contact Naue with project area, slope geometry and subsoil conditions. Grade selection, overlap design and installation method are confirmed before order.

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