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Germany: "We cannot keep producing substrates that aren’t fully recyclable"

"The hydroponic market is growing rapidly, requiring large volumes of substrates every year. However, the substrates currently in use are not sustainable due to several factors," explains Bilitis Vanicela, researcher at DITF, the German Institutes of Textile and Fiber Research.

"The high energy required to produce rockwool, the destruction of biodiverse wetlands during peat extraction, long-distance transport, and the challenges of composting coconut coir all contribute to a significant environmental impact. We cannot endlessly produce substrates that are not fully recyclable," Bilitis explains.

All aspects, before mentioned, led to the development of a textile-based substrate created for hydroponic farming. Launched recently, the substrate is the result of the three-year international research project "CirCulTex" involving six research institutions and companies from Germany and India, which was first showcased at Greentech this year.

"An inert product"
"In our search for a solution, we ultimately chose textile, as it has been tailored for specific applications for thousands of years. Used in many fields, from clothing to surgical sutures, a textile-based substrate is made of 100% polyester and therefore an inert product. Through its advantage of being washable, refreshable and finally endlessly recyclable, it offers great potential for indoor farming," explains Bilitis.

The textile consists of coarse and robust filaments that do not release microplastics. To date, all Raman Microscopy tests for microfibers, conducted at the University of Hohenheim, show no microfibers inside the crops that have been cultivated on the textile.

Throughout the study amongst others the substrate fresh matter yields, physical properties like water holding capacity, air-water ratio were consistently tested against rockwool and coconut coir. "During the research project, we have focused on leafy vegetables and herbs due to the given capacities," adds Bilitis. The findings revealed that the results obtained from the textile-based substrate were comparable to those from other cultivars.

What makes the substrate different?
Unlike other substrates, the textile substrate can be fully re-used, and cleaning takes approximately 2–3 hours depending on different aspects. The washing process does not affect the composition of the material as well as its physical and chemical properties, as the same cleaning method for hydroponic systems is deployed. "We have to deal with waste water during the cleaning procedure. There is no harm in spreading diseases because washing comes after disinfection."

As Bilitis points out, the washing procedure is done in a washing machine. These devices run very efficiently nowadays. Subsequently, there should be a sustainable way to treat the waste water anyway, according to the researchers.

"Even after cleaning it 20–30 times, the substrate can still be repurposed into new fabric," explains Bilitis. "In order to create a reusable polyester substrate, the sterilization process is done either through heat or chemicals. With heat being the more eco-friendly option, remaining roots are removed, and so the substrate is completely washed."

This can be done on-site or by professional cleaners, ensuring the substrate is pathogen-free and ready for reuse. The pricing for the textile substrate is competitive with rockwool. The cost of the textile substrate is individual, as it depends on the number of reuses.

Suitable for many applications
The polyester product is available from up to 150 cm in large and cut into strips by the industry partner based on the desired width. Rolled into the required thickness and converted into rolls, the substrate is suitable for all types of trays. The research does come to an end, and Bilitis and her team leave it to the industry to take it over. They are looking now for partners, which they expect to find in a few months.

For more information:
DITFL
Bilitis Vanicela
[email protected]
www.ditf.de

The research was carried out with partners from Germany and India:
Eschler Textil GmbH - Balingen, Germany: Michael Walter
University of Hohenheim (340B)- Stuttgart, Germany: Dr. Bastian Winkler HariMitti Agro Pvt Ltd - West Bengal, India: Suhrid Chandra
Bidhan Chandra - Krishi Viswavidyalaya - Kalyani, West Bengal, India: Dr. Sanjit Debnath
Amity University Kolkata - West Bengal, India: Dr. Harshata Pal