The textile industry is changing. More and more spinning mills are moving towards a circular economy and processing mechanically recycled fibres. Sustainability is no longer just a goal – it is a measurable business target. For spinning mills, this means thinking ecologically and acting profitably at the same time. The right blending strategy and the choice of carrier fibres are key to achieving both.
Long before terms such as „circular economy“ or „carbon footprint“ entered industrial vocabulary, automated rotor spinning was already the preferred method for processing recycled cotton. For many years, recycled cotton played only a secondary role – virgin raw cotton dominated the stage. Today, the picture has changed. Recycled fibres represent a new consumer awareness – and a strategic competitive advantage for spinning mills. Those who can process them efficiently and consistently into high-quality yarn will secure their place in the sustainable textile production of tomorrow.
The processing of mechanically recycled cotton fibres begins long before the spinning process. The right blending strategy is decisive for the final yarn quality. As mechanically recycled cotton fibres become shorter during the recycling process and exhibit greater fibre irregularity, carrier fibres are required to provide stability to the sliver and improve spinnability.
Until recently, polyester fibres (PES) were the preferred choice as carrier fibres. They offer high tenacity, consistent fibre lengths and are economically attractive -- allowing spinning mills to process high proportions of recycled cotton while meeting yarn quality and productivity requirements.
This white paper outlines the technological parameters for spinning mechanically recycled fibres on the Autocoro 11 rotor spinning machine. The values were evaluated in extensive practical trials at our spinning centres around the world, enabling even companies with limited experience in processing recycled fibres to get started with ease.
In principle, recycled fibres can also be spun on semi-automatic rotor spinning machines. However, to keep the increased number of end breaks – and the associated manual interventions – at an acceptable level, semi-automatic machines are typically operated at significantly reduced rotor speeds and withdrawal speeds.
The fully automatic Autocoro 11, by contrast, enables considerably higher production speeds while maintaining high process stability and economic efficiency, thanks to its technology specifically designed for recycled fibres.
As the textile industry shifts towards closed material cycles, the requirements for fibre blends are also changing. While cotton-polyester blends deliver technically sound results, they complicate subsequent recycling and limit the potential for a truly circular economy. As a result, mono-material concepts are gaining ground, in which high-quality, longer cotton fibres are used as carrier fibres for mechanically recycled cotton. These cotton fibres are, however, 15–20% more expensive than virgin polyester fibres and 50–60% more expensive than recycled polyester fibres.
Spinning mills face the challenge of balancing high amounts of recycled content, economical production and the requirements of a circular textile economy.
Recycled cotton fibres have a unique character, particularly when sourced from post-consumer textiles — that is, worn, washed and aged garments. Fibre quality can vary considerably depending on the pre-treatment and sorting processes. This means that every batch can be a surprise for the spinning mill.
Working with recycled cotton follows its own rules. The fibres are not always easy to handle. The good news is that there is a fully automatic rotor spinning machine that can handle this challenge: the Autocoro 11 by Saurer. Equipped with pioneering Recycling Xtreme features, it produces yarns with ahigh recycled content more efficiently and with maximum cost-effectiveness.
While polyester fibres – whether virgin or recycled – are very consistent in length, recycled cotton is different. During mechanical recycling, fibre length drops drastically to an average of 13–15 mm – roughly half the length of virgin cotton. The short fibre content is three to four times higher. The variance in fibre length distribution (UI%) can reach up to 28%, compared to around 12.5% for virgin cotton and below 8% for polyester.
| Key parameters of recycled and virgin fibres | Average fibre length | Short fibre content | Distribution of the fibre length |
| 100 % Recycled cotton Post consumer textiles | 14.1 | 44.2 | 73.6 |
| 100 % Virgin cotton | 26.6 | 8.2 | 87.5 |
| 100 % Virgin PES | 32.8 | 5.4 | 91.2 |
| 100 % Chemical recycled PES | 33.0 | 5.1 | 92.3 |
Table 1 Key parameters of recycled and virgin fibres.
In textile practice, processing yarns with a recycled cotton content of more than 70% from post-consumer waste presents a particular challenge. The reason: these yarns often fail to reach the minimum tenacity of around 8 cN/tex required for trouble-free processing on knitting and weaving machines. Insufficient tenacity leads to an increased number of end breaks and associated efficiency losses in production.
As a result, such high proportions of post-consumer recycled fibres are currently only used in isolated cases in the coarse count range of apparel textiles. Here, the coarser yarn count – with a higher number of fibres in the cross-section – can partially compensate for the lower fibre tenacity.
Where a mono-material approach using exclusively recycled raw materials is the goal, a combination of post-consumer and pre-consumer recycled cotton is recommended. While post-consumer cotton is recovered from used textiles, preconsumer waste originates from cutting residues in garment production and generally exhibits better fibre properties. By intentionally blending these two material types, the required minimum tenacity can be achieved in medium-count yarns without compromising the mono-material recycling principle.
| Materials | Fibre strength cN/tex | Fibre elongation % |
| Fibre flock recycled cotton | 7.3 | 4.8 |
| Fibre flock virgin PES | 31.8 | 43.2 |
| Sliver draw frame: 65/35% recycled cotton/PES | 29.3 | 28.2 |
Table 2 Fibre strength and elongation in cotton, polyester and the blended sliver
| Material | Average fibre length | Short fibre content | Distribution |
| Fibre flock recycled cotton | 14.1 | 44.2 | 73.6 |
| Fibre flock virgin PES | 29.4 | 6.9 | 90.3 |
| Sliver carding machine: 65/35% recycled cotton/PES | 27.4 | 8.1 | 82.5 |
| Sliver draw frame: 65/35% recycled cotton/PES | 27.2 | 8.3 | 81.2 |
Table 3 Changes in fibre resp. sliver parameters due to blending of recycled cotton with polyester
The resulting Autocoro yarns achieve strengths of almost 10 cN/tex at 8% elongation. The CV (%) value, a measure of yarn irregularity, is just 13% – an excellent figure for a blended yarn containing recycled cotton.
These yarns can therefore be used without restriction in knitting and weaving.
The use of recycled cotton is regarded as the holy grail of sustainable textile production. However, sustainable production on an industrial scale can only become established once recycled fibres can be processed in a cost-effective manner.
| Yarn description | Yarn strength cN/tex | Yarn elongation % | Yarn eveness CV % |
| Autocoro yarn Ne 19/ Nm 32 65/35% recycled cotton/PES | 9.9 | 7.8 | 13.1 |
Table 4 Yarn quality of Autocoro yarn made from recycled cotton
Saurer recognised the growing importance of recycled materials and the increasing demands on their processing as a trend already many years ago.
With the Recycling Xtreme configuration, the Autocoro 11 has been specifically developed to meet the challenges of recycled fibres. As a fully automatic rotor spinning machine, the Autocoro 11 pursues a clear objective: maximum economic efficiency at minimum spinning costs – particularly when processing demanding raw materials. The Recycling Xtreme technology enables stable and efficient processing of fibres with highly variable properties, supporting the use of high recycled content in yarn production.
Even the heterogeneity typical of recycled fibres – in terms of fibre length, fineness and cleanliness – is reliably managed by the Autocoro 11 with Recycling Xtreme. This allows sustainable yarns to be produced economically, without compromise on productivity or quality.
Synchropiecing 60 – the simultaneous automatic piecing of 60 spinning positions at once – compensates for potential productivity losses caused by end breaks and yarn clearer cuts when spinning recycled fibres, which on semi-automatic rotor spinning machines would require manual intervention. As a result, the Autocoro 11 can be operated at significantly higher rotor speeds and withdrawal speeds – up to 50% above those of comparable semi-automatic machines.
The result is consistently high machine efficiency and maximum productivity. At the same time, labour-intensive operating, piecing and cleaning processes are eliminated – a decisive advantage in the face of rising labour costs.
The Autocoro 11 offers a range of decisive advantages when processing recycled fibres. It achieves up to 50% higher productivity than comparable semi-automatic rotor spinning machines. At the same time, energy consumption per kilogram of yarn is around 10% lower than that of its predecessor and up to 25% lower than that of semi-automatic rotor spinning machines. This not only reduces production costs but also improves the environmental footprint of yarn manufacturing.
Additional efficiency gains are enabled by the Recycling Xtreme configuration. It reliably removes fibre fragments and dust deposits from machine surfaces, extending cleaning intervals and increasing machine availability. Downtime is minimised and productivity further enhanced.
Thanks to the high degree of automation, labour costs can be reduced by around 75% compared to semiautomatic rotor spinning machines. At the same time, the three-chamber waste system ensures particularly efficient raw material utilisation by automatically returning spinnable fibres to the production process. This minimises raw material losses and makes optimal use of valuable fibres. All of these advantages contribute to reducing resource consumption, increasing machine availability and lowering operating costs – a win-win situation for both the spinning mill and the environment.
| Yarn and machine type | Energy costs €/ton yarn | Personal costs €/ton yarn |
| Semiautomatic rotor spinning machine 65,000 rpm, Alpha e 3.7 | 169.2 | 81.9 |
| Autocoro 11 98,000 rpm, Alpha 3.7 | 40.6 | 61.1 |
Table 5 Labour and energy savings with the Autocoro 11
The Autocoro has been used successfully for processing recycled fibres for decades. In combination with Belcoro spinning components specifically suited to recycling applications, maximum yarn quality and process efficiency can be achieved even from demanding recycled raw materials.
One decisive success factor is the precise control of short cotton fibres throughout the spinning process. This keeps short cotton fibres incorporated into the yarn rather than being accidentally rejected. Specially tuned fibre beards play a key role here, particularly the medium-length variants. These have demonstrated their effectiveness with recycled cotton by removing impurities without losing valuable fibres. As recycled cotton has a high short fibre content, the fibres must be stably embedded within the yarn core. Belcoro rotors with a narrow T-groove provide optimum grip, which is ideal for producing consistent, strong woven and knitted yarns. For yarns made from virgin raw cotton, however, rotors with an open G-groove are more commonly used to offer longer fibres greater freedom of movement.
To ensure that even the shorter fibres of recycled cotton are reliably anchored in the yarn, a finely tuned spinning technology is are required. A decisive lever here is the rotor diameter. Compared to processing virgin raw cotton, slightly larger rotors are generally used with recycled material. They generate higher centrifugal forces, which are necessary to draw even short fibres securely into the yarn structure. At the same time, the rotor runs at a slightly reduced speed – giving short fibres more time to align and integrate optimally. The result: a consistent, firm yarn with a pleasantly soft handle.
In blends containing polyester, special Belcoro opening rollers such as the S 21 DN ensure that the sensitive polyester fibres are protected from damage and can fulfil their supporting function within the yarn. The finishing touch is provided by the Belcoro take-off nozzle K4-A: it applies the final twist, anchors the fibres securely in the yarn core and stabilises the spinning process. The result is high-quality yarn with excellent evenness and tenacity – delivering not only superior quality but also economic and sustainability benefits.
Recycled fibre processing is not only good for the planet – it also delivers a clear commercial advantage for spinning mills today. Recycled cotton is significantly cheaper than virgin cotton in many markets – in India, for example, the current price saving is up to approximately 20%. Yarn prices for yarns containing recycled cotton fibres vary by market: in India, they are around 10% lower than for yarns made from virgin cotton fibres; in Pakistan the price is around 7% higher; and in Bangladesh the price difference between virgin and recycled cotton fibres is minimal.
Through the combination of lower raw material costs, high efficiency, reduced energy consumption and lower labour costs, owners of the Autocoro 11 benefit from an excellent return on investment (ROI). Investments pay back quickly – while at the same time making a significant contribution to global resource conservation.
Recycled fibres are known for their ecological advantages – yet the figures continue to impress. Growing one kilogram of virgin cotton requires up to 11,000 litres of water. Recycling cotton, by contrast, consumes only around 600 litres – a saving of more than 90%. An Autocoro 11 with 816 spinning positions, producing a medium-count knitting yarn with 65% recycled cotton, saves up to 12.5 billion litres of water per year – compared to processing virgin cotton. That is equivalent to around 5,000 Olympic swimming pools – per machine, per year. At the same time, every Autocoro 11 reduces the annual demand for agricultural land used for cotton cultivation by the equivalent of more than 2,000 football pitches.
A further sustainability benefit arises from the use of recycled, already-dyed fibres. Since the fibres retain their colour from the original textile product, the energy- and water-intensive dyeing process can be eliminated entirely or reduced significantly. This allows water consumption in yarn and textile production to be reduced enormously, while at the same time lowering the use of chemicals and energy.
The future of environmentally friendly textiles depends on the economical processing of recycled fibres. The circular economy will only become the industry standard when sustainability and profitability go hand in hand. Modern rotor spinning technology paves the way for this.
For spinning mills, this is a demanding balancing act, involving recycled content, yarn quality, processability and cost. This is precisely where innovative spinning technologies are essential. With the Autocoro 11 and the Recycling Xtreme configuration, which has been specifically developed for recycled fibres, Saurer demonstrates that even the most demanding recycled blends can be processed economically and reliably.
As the textile industry shifts towards closed material cycles, the requirements for fibre blends are changing too. While cotton-polyester blends produce technically sound results, they can make the subsequent recycling of textiles more difficult. Separating different fibre types is still complex and limits the potential for a truly circular economy.
As a result, new blending concepts are becoming increasingly important. Instead of synthetic carrier fibres, high-quality, longer cotton fibres are becoming more attractive for stabilising the properties of mechanically recycled cotton. These monomaterial approaches enable yarn and textile constructions that are made entirely from cotton, which makes them significantly better suited to future recycling processes.
However, broader market adoption has so far been hindered by economic factors. The high-quality cotton fibres required for these applications typically cost up to 60% more than recycled polyester fibres. For this reason, mono-material concepts have gained only limited acceptance to date. However, with growing demands.
August 2026 | Version 1.0
