Biodegradable growth covers for more sustainable forest protection

To support more sustainable forestry, Sachsenröder developed a biodegradable alternative to conventional tree shelters as part of a collaborative project funded by the Agency for Renewable Resources (FNR). This solution is based on NAVUTEC® WH vulcanized fiber and coated with our partially bio-based INSQIN® textile coating technology. These innovative and more environmentally friendly tree shelters decompose after their use phase and thus make an active contribution to the protection of forest ecosystems.

Forests play a vital role in carbon storage and oxygen production. With climate change causing more extreme weather conditions, demand for resilient, near-natural reforestation is on the rise.

However, conventional tree shelters made of polypropylene, which are used to protect tree seedlings, often remain in forest ecosystems and eventually break down into microplastics. This burdens the flora and fauna. 

For Sachsenröder, the central task was to develop a more environmentally friendly, biodegradable alternative that could not break down into microplastics and would still provide the necessary protective functions.

Foresters and material manufacturers face a shared challenge: protecting young trees for around five years—enough time to take root—without harming the environment.

Tree shelters must protect young seedlings during their critical growth phase from frost, browsing by wild animals, and competing vegetation. They must also be able to biodegrade naturally, without requiring special treatment or labor-intensive collection.

The special technical challenge lay in developing a material that, on the one hand, would provide sufficient durability and weather resistance throughout its service life, and on the other hand, was biodegradable. Because pure vulcanized fiber does not have sufficient long-term durability and dimensional stability under natural weather conditions, a special coating solution had to be developed.

To support more sustainable reforestation, materials manufacturer Sachsenröder joined the non-profit collaborative TheForestCleanup project to design biodegradable tree shelters. 

TheForestCleanup is a consortium of companies and research institutions that work to reduce plastic in forest ecosystems. The development work was awarded the 2023 Excellent Technology Transfer Neckar-Alb prize by the IHK Reutlingen and the Eberhard Karl University of Tübingen.

Building on 140+ years of materials science innovation, Sachsenröder developed a prototype of NAVUTEC® WH—a tree shelter material made from 100% renewable raw cellulose which is converted into vulcanized fiber through parchmenting. The cellulose used comes from certified European forestry. White pigments, dyes, and fillers are deliberately avoided. Unfortunately, the first design, made of pure uncoated vulcanized fiber, did not show sufficient long-term durability and dimensional stability under natural weather conditions,  making it unsuitable for real-world use. 

To improve the initial design, Sachsenröder approached us to support them in developing a hydrophobic coating that could preserve and protect the tree shelters, and could still naturally biodegrade after around five years. Together with Sachsenröder, we explored various formulations until we uncovered the optimal solution: a hydrophobic coating created with our partly bio-based Impranil® CQ polyurethane dispersion. 

Based on our INSQIN® textile coating technology, this coating offers the necessary weather resistance during the use period for the internal and external parts of Sachsenröder’s tree shelters. Compared to uncoated vulcanized fiber, the coating enables a controlled delay of biological and photo-oxidative degradation until the protective function is fulfilled, and the tree shelter is no longer needed. Crucially, the coated tree shelter is certified biodegradable according to DIN EN ISO 17556:2019**, tested by the Hohenstein Institute for Textile Innovation gGmbH, and leaves almost no traces in nature after degradation.

In collaboration with The Rottenburg University of Applied Forest Sciences (project management) and the Hohenstein Institute for Textile Innovation, several hundred prototypes were deployed in test areas in four federal states in Germany under real conditions. Long-term tests are currently ongoing. Supplementary laboratory tests have already confirmed the residue-free decomposition of the coated tree shelters under soil conditions similar to those in a forest.

The previous tests show not only that the coated tree shelters are biodegradable, but also that the partially bio-based content in the coating formulation contributes to reducing the product's CO₂ footprint. *** 

* Agency for Renewable Resources (FNR) 
**Tested by the Hohenstein Institute for Textile Innovation gGmbH
***According to internal calculations