Viscose, modal, and Tencel (Lyocell) are all cellulose fibers — they start as wood pulp from trees and end up as a soft, drapey, breathable fabric. The chemistry that gets them from tree to fiber is where the environmental footprints split hard.
Here's what's actually different, what to look for on a spec sheet, and how to make an honest claim.
How each one is made
Viscose (also called rayon) is the original regenerated-cellulose fiber, patented in the 1890s. The process: wood pulp is dissolved in carbon disulfide (a toxic solvent), extruded through a spinneret, and regenerated into fiber in a sulfuric-acid bath. The solvents are recoverable in principle but routinely released at poorly-managed facilities, and factory-worker exposure to carbon disulfide has documented neurological health consequences.
Modal is a second-generation viscose. Same basic chemistry, but with higher wet strength, finer fiber, and (when produced by reputable mills) stricter solvent recovery. Lenzing's Modal specifically uses beech wood from managed European forests and recovers a high percentage of its process chemicals.
Tencel Lyocell (Lenzing trademark) is a third-generation cellulose process. Wood pulp is dissolved in a non-toxic organic solvent called NMMO, extruded, and regenerated. The closed-loop process recovers around 99% of the solvent. Wood is sourced from FSC- or PEFC-certified forests. By any reasonable environmental measure, Lyocell is dramatically better than conventional viscose.
What this means for a claim
- "Viscose from certified sources" (e.g. FSC, PEFC) — a meaningful but limited claim. Covers the wood, not the processing chemistry.
- "Lenzing Modal" / "Lenzing Viscose / EcoVero" — brand-specific claims that tie the fiber to Lenzing's traceability and process standards. Stronger than generic modal/viscose.
- "Tencel Lyocell" — the strongest cellulose claim in wide commercial availability. Closed-loop solvent, certified wood, traceable.
- "Bamboo viscose" — tricky. The bamboo at farm level is typically low-impact, but the conversion to fiber uses conventional viscose chemistry. The "bamboo" in a finished fabric no longer has any meaningful property of bamboo; it's regenerated cellulose that started as bamboo pulp.
Trade-offs beyond sustainability
- Hand feel: Lyocell is smoother and drapier than modal; modal is silkier than viscose; viscose at equivalent weight is more prone to wrinkling.
- Durability: Lyocell > modal > viscose, especially wet strength
- Cost: Lyocell > modal > viscose
- Biodegradability: All three are biodegradable in principle; Lyocell usually biodegrades fastest
- Blends: All three blend well with cotton, linen, or wool for structure and price balancing
A practical sourcing rule
If you're making a sustainability-forward product, specify Tencel Lyocell or Lenzing Modal by brand name in your tech pack, not "viscose" or "modal" generically. The brand-name spec ties the fiber to a traceable supply chain; the generic spec lets the mill substitute whichever conventional viscose is cheapest that week.
For a factory quote, expect Tencel Lyocell to cost 15-30% more than generic viscose at the same weight and construction. That delta typically shows up as $1-3 per piece at wholesale — usually worth it, sometimes not.
Frequently asked questions about cellulose fibers
Is bamboo fabric the same as viscose?
Functionally, yes. Almost all "bamboo fabric" on the market is bamboo viscose — bamboo pulp dissolved and regenerated using the same carbon-disulfide chemistry as any other viscose. A true mechanically-processed bamboo fiber (bamboo linen) exists but is rare and has a very different hand. If you're buying "bamboo" and the label says "viscose" or "rayon," it's the same environmental profile as any other viscose — minus the farm-level footprint, plus whatever greenwashing the word "bamboo" implies.
Does Tencel shrink?
Tencel Lyocell has excellent dimensional stability — minimal shrinkage (usually under 3%) in properly-finished fabric. Tencel Modal is similar. Where shrinkage shows up is in blends with cotton, especially if the fabric wasn't pre-shrunk (sanforized) before cutting. Spec pre-shrinking on your tech pack if you're running a cotton/Tencel blend.
How do I specify Lyocell vs generic viscose in my tech pack?
Write "Tencel Lyocell" or "Lenzing Lyocell" by brand name, not just "lyocell" generically. Tencel is Lenzing's trademark and comes with traceability paperwork the factory can verify. Without the brand spec, factories may substitute generic lyocell from other sources — which may or may not come from a closed-loop process. Add a clause in your PO requiring the factory to present the Lenzing fiber certificate on request.
Are any of these biodegradable?
All three are biodegradable in principle since they're regenerated cellulose from plant source. Lyocell degrades fastest (typically 8-10 weeks in compost), modal next, conventional viscose slowest. None of them biodegrade meaningfully in a landfill, though — you need oxygen and moisture. Blends with synthetic fibers (polyester, nylon, elastane) don't biodegrade at all.
Related reading
- GOTS vs "Organic Cotton": What's Actually Certified — how fiber certifications work when you blend Tencel with cotton.
- Deadstock Fabric: Pros, Cons, When It Makes Sense — the alternative path to low-impact sourcing.
- Writing a Tech Pack: What It Needs to Contain — specify Lyocell by brand name or risk a generic-viscose substitution.
Found this useful?
Share it with your network
