The unseen output of spinning mills: up to 11% fiber becomes “waste.” Here’s how it’s turning into product — and profit

Worldwide fiber production topped 100 million tonnes by 2017, according to industry research (IntechOpen). Inside spinning mills, the basic arithmetic is stark: 6–11% of that input typically ends up as waste during cleaning, opening, carding and combing (IntechOpen) (IntechOpen). One Brazilian snapshot: 167,850 kg of cotton consumed yielded 19,086 kg of spinning waste — roughly 11% (IntechOpen).

That “waste” isn’t monolithic. It spans blown cotton dust, card flats, combing noils (short fibers removed during combing), sliver tail scraps (sliver is the untwisted rope of fibers post-carding), roving bits (slightly twisted sliver prior to spinning) and broken thread or “fly.” Dirty blowroom waste (the opening/cleaning stage) can be only ~35–55% good fiber, while carding/sliver waste often exceeds 80% fiber (IntechOpen). Roughly 6–8% of inputs become primary mill waste containing ~50% fiber (IntechOpen), and, accounting for downstream blends, spinners routinely recover ~90%+ of that fiber — with ≈6% residual trash — back into product (IntechOpen).

Recycling back into yarn production

One straightforward route is reintroducing cleaned waste into yarn. Modern lines blend “good” waste (e.g., sliver noils and filtered fly) at modest levels: fine ring and rotor yarns (ring spinning is the conventional twist insertion; rotor or open‑end spinning feeds fibers into a high‑speed rotor) often tolerate ~2.5–5% rebonded waste, while coarse open‑end yarns can include 10–20% recycled fiber (IntechOpen). Mills prefer returning each waste type to its original mix — card waste back into carded yarns, combing noils to rotor yarns — to stabilize quality.

Studies consistently show surprisingly high headroom. Blends with up to ~20% waste typically cause acceptably minor property changes (IntechOpen). Wulfhorst (1984) reported “up to 20%” reclaimed fiber without noticeable yarn‑quality declines (IntechOpen). Halimi et al. found blend uniformity and irregularity unchanged up to 25% waste in rotor‑spun yarns (IntechOpen).

There are trade‑offs. In practice, upping waste from 5→40% shortened tenacity and raised imperfections: one study recorded ~22% lower breaking strength in ring‑spun yarn and 52% lower in rotor‑spun yarn (IntechOpen). Another trial found 50% waste‑blend rotor yarns had ~20–25% lower strength and 21–22% higher hairiness, yet up to 30% waste produced only modest increases in thick/thin faults (IntechOpen). Fabrics made from 100% recycled fiber showed higher hairiness and lower tensile strength than virgin yarns but met technical requirements in targeted uses (IntechOpen) (IntechOpen). The cost case is strong because recycled fiber is essentially “free” raw material. In practice, mills lean heavily on clean waste (sliver noils, filtered fly can approach 50–100% reuse) and keep dirty waste levels lower (≤30% in open‑end; ≤10% in ring) to balance quality (IntechOpen) (IntechOpen).

Nonwovens, insulation, and composites

When not re‑spun, waste fibers head to nonwovens and insulation. Spinning byproducts were chemically bonded into nonwoven fabric with tearing strength up to ~23 g using 25% polyvinyl alcohol as binder (ResearchGate). Recycled‑denim fiber mats delivered ~0.131 W/m·K thermal resistance at 20–40% fiber content, comparable to polystyrene insulation (ResearchGate). One review found textile waste panels can match or exceed conventional insulators, performing similarly to XPS (extruded polystyrene) foam or mineral wool (IntechOpen).

Waste fibers also act as fillers in composites. Reviews report cotton, jute, hemp and other textile wastes embedded in polymers, concrete and natural binders to create construction panels and auto parts (MDPI). Examples include cotton fiber/polyester blends pressed into cement blocks or epoxy boards, improving stiffness and thermal mass.

Industrial and consumer byproduct uses

Lower‑quality laps and noils are blended into industrial yarns for mops and rugs, or into nonwoven fillings. Historically, mills baled wastes into “cotton batting” for mattresses and upholstered furniture (ILO Encyclopaedia). One industry guide notes ring‑spinning waste is often sold to make mop yarns, while carding (“garnetting”) waste is pressed into bedding insulation (ILO Encyclopaedia). In Indonesia, Asia Pacific Fibers (APF) points to a “textile‑to‑textile” program turning second‑hand clothes into new fiber blends (Asia Pacific Fibers).

Pyrolysis and material recovery

Cellulose‑rich wastes can be thermochemically converted. Pyrolysis (thermal decomposition without oxygen) of pure cotton waste yields roughly 45% liquid oil (mostly heavy naphtha) and a carbon‑rich char (~75% carbon) that can serve as activated carbon (ScienceDirect). Mixed cotton/polyester waste yields mostly combustible gas (H2‑rich) (ScienceDirect). These routes indicate waste fibers can become fuels or adsorbents, potentially powering on‑site boilers (boilers) or providing raw materials for chemical industries (ScienceDirect). In principle, waste cotton could also be processed into cellulosic ethanol or furfural (ScienceDirect). The char pathway links directly to the widespread use of activated carbon in industrial applications.

Disposal routes and regional trends

When waste isn’t reused, it’s often incinerated or landfilled — both contentious. Incinerating textile waste emits toxic gases such as furans and dioxins, a risk flagged in a Reuters analysis of Asian textile hubs (Reuters via WSAU). That analysis warns unmet recycling capacity leaves the rest to clog bodies of water, pollute soils or be incinerated (Reuters via WSAU).

In the EU, separately collected textile waste treated in 2022 was ~1.38 million tonnes; of that, ~12% went to landfill and 15% to incineration (EEA). If including mixed municipal waste, about 73% of discarded textiles still end up burned or landfilled (EEA). By contrast, India recovers ~60% of its 4.7 Mt textile waste (Reuters via WSAU).

Energy recovery is a bridge option. Modern boilers can burn clean textile waste (cellulosic content) alongside lignite or biomass, though polyester’s fossil origin reduces heat value and raises SO₂/NOₓ concerns. More sustainably, pyrolysis (above) can recover energy and materials. Landfilling is increasingly discouraged by regulation (e.g., forthcoming EU Waste Textiles rules). In Indonesia, environmental law (Law 32/2009) and Ministry of Environment standards classify textile scraps as non‑B3 (non‑hazardous), requiring licensed handling and proper disposal (Rafika Transindo). Major Indonesian fiber producers reference the national Circular Economy Roadmap — which “prioritizes the textile industry” — and pledge textile‑to‑textile recycling streams (Asia Pacific Fibers) (Asia Pacific Fibers).

Handling and conveying constraints

Waste fibers are bulky, low‑density and flyaway, which complicates transport and conveying. Mixed short fibers (“fiber fly”) are best collected pneumatically: modern mills use central vacuum systems to suck waste from machines into hoppers, cutting labor and dust exposure (ILO Encyclopaedia). Collected waste then needs compaction. Classic “wastehouses” accumulated scrap until it could be baled — around 200+ kg per bale (ILO Encyclopaedia). Today, horizontal bale presses automatically compress vacuum‑collected waste (ILO Encyclopaedia).

Risks persist. Lint carries dust and static; ducting must be leak‑tight and explosion‑protected. Waste mix variability adds steps: one mill’s blowroom waste was “very dirty” (≈22% trash such as leaf and seed hull), requiring de‑contamination before reuse (ResearchGate). Short fibers clump easily; high “nep” counts (tiny entangled fiber knots) in rotor yarns have been traced to card waste inclusion (IntechOpen). Belt conveyors can jam as fibers entangle, so layouts often favor vertical suction and baling over long open conveyors. Keeping waste‑blend ratios steady is operationally complex, forcing careful inventorying of sorted waste. Net‑net, large volumes of light, mixed waste fibers demand dedicated infrastructure (vacuum collection, sliver breakers, bale presses) and tight moisture/dust control.

Market signals and cost calculus

Global textile recycling is scaling. One analysis pegs the market at about USD 9.4 billion by 2027 (Reuters via WSAU). Policy pushes (EU’s Ecodesign for Sustainable Products) and corporate programs such as APF’s “Sustainable Stitch” show accelerating adoption (Asia Pacific Fibers).

Technical studies repeatedly find that returning 15–25% spinning waste to blends meaningfully reduces raw‑material cost and landfill volume with moderate quality trade‑offs (IntechOpen) (IntechOpen). For decision‑makers, that points to a pragmatic playbook: invest in automated suction/baling, define outlet tiers (back‑to‑yarn, nonwovens, composites, or energy/pyrolysis), and turn a disposal cost into value streams — cheaper fiber inputs, insulation or composite feedstock, or energy feedstock — provided handling complexity is managed and quality specs are clear (IntechOpen) (IntechOpen).