A new crop of biomaterials
The agricultural and food industries generate waste products that can yield valuable raw materials to make fibres or dyestuffs... but only if the cellulose or colouring agents from these leftovers can be cost-competitively extracted and scaled.
Few of us ever take a moment to think about the processing of leftovers generated by the rice we eat, the orange juice we drink or the thyme we sprinkle over a dish we prepare. While the fashion industry is often criticised for the waste it generates, agriculture and the food industry may have even worse track records. For many, these are not residues but rather resources, and should therefore be considered co- or by-products. Plants are mostly cellulose (eat your fibres!), and it is the most abundant natural biopolymer. On paper (cellulose too!), turning this unused biomass into fibres seems like a good idea.
In its report, ‘Spinning future threads’, published in June 2021, the Laudes Foundation (formerly the C&A Foundation) took a close look at those agricultural residues that could be suitable raw materials for fibres. It believes that innovation in this field “offers strong potential to decrease extensive crop burning and its associated negative environmental and climate impacts; generate new, additive low-cost revenue streams for low-income agricultural communities in Asia, and activate a scalable and more sustainable source of fibre for the fashion industry.”
The report identifies husks and straw from rice and wheat, empty fruit bunches from oil palm, sugarcane bagasse and banana plantain waste as having potential in textiles, as either new agricultural fibres or as a source of cellulose pulp for manmade cellulose fibres (MMCFs). These biomass conversion pathways would not increase land under cultivation or crop volumes, which the Foundation argues against.
Stalking hemp
This potential is already being investigated by a number of material innovation companies, from Circular Systems in the United States to Nanollose in Australia. Earlier this year, Fashion for Good launched a research programme ‘Untapped Agricultural Waste Project’ to validate and scale technologies that could successfully transform agricultural waste into sustainable textile fibres, with funding from the Laudes Foundation. This field is also the focus of research and development at many MMCF producers.
Hemp crop residues are on top of the list of possible resources for many of these projects. The cellulose content of dried hemp is around 57%, according to the Nova Institute in Germany, while that of wood is said to be in the 40% to 50% range and cotton fibre is 90%. Circular Systems’ Agraloop Biofibre platform draws its raw material from the leftovers of flax crops farmed for their seeds or for cannabidiol (CBD). “In North America alone, one million acres (400,000 hectares) of oil-seed flax is planted. This is amazing biomass that is going to waste,” says Circular Systems cofounder and CEO, Isaac Nichelson. The company currently sources its raw materials from oil-seed hemp grown in France and flax in Belgium.
The production of Agraloop BioFibres starts with a pre-processing phase, in which the fibre is decorticated. This operation is conducted as close to the farm as possible and then shipped to a centralised biorefinery. The company’s wet processing technique uses a “bio-appropriate chemical that purifies the cellulose of stems and leaves into fibre bundles that can be spun into yarns,” says Mr Nichelson. The result is a natural fibre yarn, he says, not an MMCF, and could be labelled linen or hemp on garments. “The yarns drawn from hemp crop waste are coarser than cotton and are suitable for denim,” he adds. Pakistan-based Naveena Denim Mills (NDM) has made denim fabrics from Agraloop BioFibre.
Circular Systems plans to investigate the potential of banana and pineapple waste, and is part of a new consortium, The Fibral Material Alliance, with Ananas Anam, Bananatex and Regenerate Fashion. Together they plan to increase market adoption of these novel plant-based materials.
French start-up RBX Créations is also working on making textile fibres from the cellulose of the unused portions of hemp crops under its Iroony label. “This biomass used to be considered waste, but we see it as a resource; it is technically a co-product,” Anne Reboux, cofounder with her brother Charles of RBX Créations, tells WSA. They maintain close relationships with farmers and have patented a method of extracting the cellulose from the feedstock they select. This pulp can be spun into fibres by different technologies such as HighPerCell developed by the German Institutes of Textile and Fibre Research Denkendorf (DITF), using ionic liquids to turn cellulose pulp into filaments. The solvent is said to be non-toxic, environmentally friendly and can be almost completely recovered. In a partnership with DITF, wet spinning tests have been conducted as part of ELIIT, an EU-funded research project. RBX Créations plans to set up an industrial scale hemp and linen pulp processing facility.
Los Angeles-based sustainable textile start-up Hurd Co is also developing a process to extract cellulose pulp from hemp agricultural waste to make Agrilose lyocell or viscose fibres. “It is a zero-waste technology that requires half the water and 350 times less energy than conventional fibre pulp processing,” says cofounder Taylor Heisley-Cook. Still in the early stages of development, the company is seeking further funding to scale up its R&D facility.
Alternative MMCFs
Manmade cellulosic fibre (MMCF) producers are quick to emphasise that their viscose, lyocell, modal or acetate yarns are made from wood pulp, a natural and renewable resource. But pressure to reduce the risk of deforestation is also pushing them to integrate alternative cellulose-rich biomass resources in their fibres.
After having experimented with orange cellulose pulp with Orange Fiber last year, Lenzing introduced a Tencel lyocell yarn incorporating 20% cellulose pulp from hemp this year. “Our interest in hemp pulp is strong,” says Michael Kininmonth, business development manager for the Austrian cellulosic fibre producer. The Orange Fibre Tencel lyocell was a limited edition, with a first production run of four tonnes.
All or most MMCF producers are investigating non-wood sources of pulp to make their fibres. The ‘Spinning Future Threads’ report says these alternative resources represent currently 7% of global virgin cellulose pulp production. In addition to working with Fashion for Good and the Laudes Foundation, India-based Birla Cellulose, an Aditya Birla Group company, is working with Nanollose to make an MMCF from microbial cellulose extracted from coconut waste.
Nanollose has identified a specific type of agroindustry waste, coconut water from aged coconuts, which “is bitter and usually thrown away,” says Dr Wayne Best, executive chairman. The company has developed specially formulated microbes that turn it into a jelly of microbial cellulose to make its “tree-free” Nullarbor pulp. The name is both that of a national park in Australia and the Latin term for ‘no tree’.
“Our research has focused from the very start on making a viscose-type fibre that is not derived from wood pulp,” says Dr Best. “The microbial cellulose pulp we have developed is 99% cellulose, it is a very pure type of cellulose.” In initial tests with Birla, the two companies found that Nullarbor-20 lyocell, containing 20% Nanollose pulp, was stronger than conventional lyocell. He believes this could be due to its high cellulose content and “the way the molecules stack”. In addition, he says, Nullarbor fibres have “a lovely hand feel”. The partnership with Birla led to the filing of a joint patent in 2021. The bacterial cellulose is currently made in China by a partner company, but Dr Best would like to have it produced in India. Surya Valluri, chief sustainability officer for Birla Cellulose, tells WSA that a pilot is under way, but that scaling it may take another 18 to 24 months.
Agroindustry dyestuffs
Fibres are not the only materials that can be drawn from agricultural waste, as Archroma has proven with EarthColors, launched in 2014. These dyestuffs are made from an array of crop residues including almond shells, orange peels and rosemary leaves. “EarthColors is a journey; we are continually seeking new unused resources as alternative raw materials,” says Nuria Estape, head of global marketing. The available colours are limited to those found in nature, and developing a full palette has proven to be a challenge, despite the company’s efforts. Achieving bright colours is another challenge, but she says research is ongoing.
“In recent months, we’ve seen a change in outlook from major fashion brands,” she says, noting that Primark has integrated the concept in its collections. “It is not the first company to use EarthColors, but it is the first to use them to such an extent,” she says, adding that the retailer has embraced the concept to the point of printing EarthColors branding directly on the clothes.
Colorau, a range of natural dyestuffs developed by Portuguese textile manufacturer Tintex, is made from food and wood industry waste using only water as a solvent. To expand the available palette, the company also continually seeks new unused resources, “but we want to use materials that are as sustainable as possible and preferably available in our region,” says Pedro Magalhães, R&D manager. Colorau includes thyme waste from a local herbal tea maker, wood industry by-products such as chestnut and gambier that are sourced in Europe. The company has set up a research programme with a local university to identify other possible local resources.
In Japan, Toyoshima’s Food Textile dyes are made from food and beverage industry waste. These include leftovers from ready-to-eat salads, coffee houses, makers of herbs or essential and vegetable oils, or jams and dried fruits. The company says it extracts natural dyes from these using a patented process that does not call on harmful chemicals nor heavy metals. They can be applied to natural-fibre fabrics and are said to have high colour-fastness. “A single ingredient can be used to make several different colours. We can produce some 500 colours from 50 different food ingredients,” said company executive Shinsuke Sakurai, speaking at an online event. His colleague Jerry Lin pointed out that the company needed to secure “a reliable source of food waste with the same qualities over time and in sufficient quantities”.
The possibilities of transforming unused biomass and food waste into new materials and chemicals are far from having been fully explored, as can be seen in the diversity of the projects under way. Admittedly, the new fibres in development have yet to reach full commercial scale, but demand is high for anything bio- or plant-based. Turning waste into viable industrial resources would further boost the appeal of this new crop of biomaterials.
Primark has introduced garments dyed using Archroma EarthColors, derived from agroindustry waste.
CREDIT: Primark
