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Materials

28: Bamboo silk

Problem:

Making silk with silk worms kills the worms and emits vapours that cause respiratory problems for workers.

Solution:

Luxurious, environment-friendly silk made from bamboo.

Bamboo silk, a popular fibre because it is breathable like cotton and cool to the touch, is used for luxury towels, bedding and linen.

Sericulture (making silk) is not considered an eco-friendly practice. Living cocoons are collected and kept under the sun, or boiled, or exposed to steam to kill the silkworms and make the cocoons easier to unravel. The boiling of cocoons leads to the formation of vapours that can pollute the environment and also cause

Bamboo can be a very sustainable crop; a fast growing grass, it requires no fertiliser and self-regenerates from its own roots, so it does not need to be replanted.

When compared to cotton cultivation, which requires large amounts of water, pesticides and labour, the advantages are pretty clear.

The first process involves combing out the bamboo fibres and spinning these into thread. This results in a slightly coarse fabric that is usually called “bamboo linen”.

Creating this “linen” is labour intensive and expensive and the result not suitable for the soft, intimate products for which bamboo is most in demand.

The second and much more popular method is the process used to make the silky soft bamboo fabric you find in sheets, underwear and more.

This “bamboo rayon” is produced through a highly intensive chemical process, similar to the process used to turn wood chips into rayon. This is where the sustainability of bamboo gets a little prickly.

The majority of bamboo is grown in China, and there is no information regarding how intensively bamboo is being harvested, or what sort of land clearing might be underway in order to make way for the bamboo.

Also, although bamboo doesn’t require pesticides, there is no guarantee that they are not being used to maximise outputs.

A similar fabric called Lyocell (also known by the brand name TENCEL) uses a closed-loop process to recapture and reuse 99% of the chemical solution.

It was developed beginning in 1972 by a team at the American Enka fibers facility at Enka, Western North Carolina and called Newcell. The fibre was developed further as Tencel in the 1980s by Courtaulds Fibres in Coventry, UK.

Tencel is often made from sustainably farmed oak, birch and eucalyptus trees with respect for the indigenous forest, and the fabric was awarded the “European Award for the Environment” by the European Union.

Bamboo Lyocell is made with pure organic bamboo pulp; it is crushed, washed and spun into yarns. Traditional lyocell is made from wood, but bamboo lyocell is a renewable plant source.

Bamboo lyocell is silky, smooth and very soft. Companies using bamboo Lyocell include Ettitude in Los Angeles for their sustainable bedding brand.

The process of making Lyocell consists of cellulose fibre made from dissolving pulp using dry jet-wet spinning. The amine oxide used to dissolve the cellulose and set the fibre after spinning is recycled. 98% of the amine oxide is typically recovered.

Since there is little waste product, this process is relatively eco-friendly.

In 2000, CVC (Citicorp Venture Capital) sold the Tencel division to Lenzing AG, who combined it with their “Lenzing Lyocell” business but maintained the brand name Tencel.

In 2004 Weyerhaeuser Company introduced a modified kraft pulp fiber that is used to generate Lyocell fibers for textiles and non-woven products. Four years later Lenzing and Weyerhaeuser teamed up to develop lyocell-based nonwoven fabrics.

In 2016, Lenzing’s Tencel Denim Team,Tricia Carey, Hale Ozturk and Michael Kininmo, launched “Carved in Blue”, a blog covering the inner workings and innovations of the denim industry and be part of a community that has a growing environmental consciousness and creativity: stories on sustainability, trends, mills, and brands including social media channels on Instagram, Facebook, Linked In, Twitter and You Tube.

Result: as of 2017, Lenzing’s Tencel brand is perhaps the most widely known lyocell fiber producer throughout the world and is building the world’s biggest Lyocell plant in Thailand.

Dr Richard Blackburn, a sustainable materials expert from Leeds School of Design, believes this extraction method could be extended to other high cellulose plant by-products such as stalks, stems and leaves, to create different types of sustainable fiber.

In August 2020 Tencel, the textile specialty fibre brand under Lenzing, has partnered with India-based textile and garment major Arvind Ltd. to launch a collection of trendy, stylish sustainable workwear shirts and suiting for men.(lenzing.com)

Patent N° US6210801B1: 2001 “Lyocell fibers, and compositions for making same.” Inventors: Mengkui Luo et al.

Discover solution 29: The diamond battery, made from nuclear waste

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