In Europe 700 million square metres of carpets are produced each year, and in the United States the volume is ten times higher.
The work has been carried out for the Netherlands companies Bond Textile Research, Best Wool Carpets and James, which own the four patents on which this new biological technology is based.
The so-called "cradle-to-cradle" model has been central to the work done by the team led by Tzanko Tzanov, a researcher with the Molecular and Industrial Biotechnology Group at the Universitat Politècnica de Catalunya. BarcelonaTech's Terrassa Campus. The outcome is an enzyme-based biological technology that paves the way for three Netherlands companies to manufacture carpets that are much lighter, sustainable, biodegradable, and 100% recyclable. At the end of their useful life, the carpets can be used as fertiliser or substrate for growing plants. The system saves a great deal of energy, completely closes the biological cycle for wool, and significantly reduces the final cost of carpet products.
For the last year, Tzanko Tzanov, one of the coordinators of the Molecular and Industrial Biotechnology Group at the UPC's Terrassa Campus, has been working in collaboration with researchers at the University of Graz (Austria) on the project, which is known as Erutan ("nature" backwards). The "back to nature" concept is at the heart of the research project commissioned by the Netherlands companies Bond Textile Research, Best Wool Carpet and James, who asked the team to come up with a technology for manufacturing wool carpets that would close the biological cycle for wool and avoid the use of latex.
Doing without latex
In line with the cradle-to-cradle philosophy, Tzanov's team focused on creating a product that can be returned to nature at the end of its useful life in the form of organic material for growing plant products. To achieve this goal they had to eliminate latex -- a material that is both heavy and expensive -- from the manufacturing process for wool carpets. Conventional manufacturing of carpets includes a system for binding the material using a layer of latex that impregnates the backing to which fibres are attached. This layer of latex (a very costly material) accounts for 70% of a carpet's weight and must be applied by means of high-temperature vulcanisation. Normally when a carpet reaches the end of its useful life it is destroyed by incineration, a process that generates greenhouse gases. Only 20% of the product is recycled.
Enzymes generate powerful adhesive
The research team focused on harnessing enzymes in the production process. The innovative system they developed starts with a thorough check of the wool used, which comes from New Zealand sheep that graze on organic pastures free of pesticides and heavy metals. When the wool reaches the production facility, it undergoes an enzyme-based pre-treatment process that cleans the material and removes all the impurities found in raw wool.
After the wool is spun and cross-linked to the carpet base, the backing is impregnated with a paste made of natural phenolic compounds and oxidative enzymes that polymerise the paste. This process produces a powerful adhesive that creates the platform to which the fibres are attached. The wool is bound in a more compact, durable way, yielding a product that beats durability standards for carpets made using conventional systems by two points.
The enzymatic treatment takes 30 minutes and comprises two stages. In the first, the carpet must be kept at a temperature of 45°C for 15 minutes, and in the second, a temperature of 95°C is maintained for an additional 15 minutes. The process uses 50% less energy than the conventional treatment, which requires vulcanisation at 100°C to treat the latex.
From carpet to substrate for growing mushrooms
A wool carpet manufactured using this innovative system is a completely natural and biodegradable product. At the end of its useful life the entire product can be shredded and turned into organic material, which can then be used, for example, as fertiliser for growing plant products. In fact, the company BVB Substrates is currently testing this organic material as a substrate for growing plants.
Carpet production is a large-scale activity. In Europe 700 million square metres of carpeting is produced each year, 55 million square metres of which is with latex backing. In the United States, the production volume is ten times higher. Mohawk Industries, the leading US carpet manufacturer, has expressed an interest in the new production system.
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