Tencel Lyocell vs Rayon: The Closed Loop Is the Whole Difference
Tencel is Lenzing's brand name for lyocell and modal fibres made from FSC-certified wood pulp in a closed-loop process that recovers more than 99 percent of the NMMO solvent. Rayon, or viscose, uses an open-loop process built on carbon disulfide and sodium hydroxide, chemicals that are discharged rather than recovered. Both fabrics start as wood pulp, and both drape well, but only one of them keeps its chemistry inside the factory.
A label that says Tencel and a label that says rayon are describing the same starting material: wood pulp, dissolved and spun into fibre. Shoppers read them as two versions of the same thing, and in a sense they are. The difference is not in the tree. It is in what happens to the chemicals after the fibre is made, and that difference is large enough to decide which one to buy.
Lenzing, the Austrian company behind Tencel, dissolves eucalyptus wood pulp in NMMO, a non-toxic organic solvent, spins it into fibre, and recovers more than 99 percent of the solvent to use again. Rayon production dissolves its pulp in carbon disulfide and sodium hydroxide in an open loop, and the chemicals leave the factory in wastewater. One process is a loop. The other is a pipe.
What the closed loop actually recovers
The number Lenzing publishes is a solvent recovery rate above 99 percent, with water fully recovered and recycled as well. That is not a marketing rounding: the NMMO is captured from the water bath, purified, and fed back into the next batch, and the loop is the reason Tencel can claim a lower footprint than generic lyocell, which Lenzing says emits about 50 percent more greenhouse gas across manufacturing. The closed loop is the product, in the sense that the fibre is only as clean as the process that made it.
Generic lyocell from other mills uses the same NMMO chemistry, but without Lenzing's recovery rates or its certified wood supply. That is why the Tencel label matters as a guarantee rather than a style word: it certifies the wood came from FSC or PEFC forests and the solvent stayed in the loop. All Tencel is lyocell, but not all lyocell is Tencel, and the gap between them is the audit trail.
Why rayon is cheaper, and what that costs
Rayon is cheaper because its chemistry is cheaper. Carbon disulfide and sodium hydroxide cost less than NMMO, and an open-loop factory does not pay to recover and purify its chemicals. The savings show up in the price tag and in the wastewater, because carbon disulfide is a neurotoxin the EPA classifies as a hazardous substance, and the factories that run open-loop viscose have a long record of discharging it. The FTC has sued retailers since 2010 for marketing bamboo viscose as bamboo, because the bamboo is gone by the time the fibre exists: the product is rayon, whatever the plant was.
The fabric itself tells the same story. Rayon weakens sharply when wet, losing much of its strength, while Tencel keeps roughly 85 percent of its dry strength when wet. That is why a rayon shirt feels fine on the rack and sags after three washes, and why a Tencel shirt holds its shape. The cheaper fibre costs more per wear, because it does not survive as many of them.
How to buy it without getting fooled
Check the label for the word Tencel, not just lyocell, and check the fibre content for the percentage. A shirt that says 70 percent Tencel and 30 percent polyester is a blend, and the polyester is doing the durability work the lyocell cannot do alone. That is not a bad shirt, but it is not a Tencel shirt in the way the tag implies, and it will not feel or wear like one.
Watch for bamboo viscose sold as a sustainable fibre. Bamboo grows fast, which is true and irrelevant, because the viscose process erases the plant and leaves the same open-loop chemistry as any other rayon. If sustainability is the reason you are buying, the label to trust is the closed-loop one, and the fibre to trust is the one with a recovery rate printed next to it.
Related reading
Readers working through “Tencel Lyocell vs Rayon: The Closed Loop Is the Whole Difference” often find these earlier guides useful as well: Super 120s vs Super 150s: The Fineness Trade Nobody Tells You About, Real Silk vs Polyester Satin: The Burn Test Settles It in Ten Seconds, and Real Linen vs a Blend: The Tests That Tell Them Apart in the Store.
Frequently asked questions
Is Tencel the same as rayon?
No, though both start as wood pulp. Tencel is Lenzing's branded lyocell, made in a closed-loop process that recovers more than 99 percent of its solvent. Rayon, or viscose, uses an open-loop process with carbon disulfide and sodium hydroxide, and the chemicals are discharged rather than recovered.
What does closed loop mean for Tencel?
The solvent used to dissolve the wood pulp, NMMO, is captured, purified, and reused, with Lenzing publishing a recovery rate above 99 percent and full water recovery. That is what separates Tencel from viscose, where the chemicals leave the factory in wastewater.
Why is Tencel more expensive than rayon?
The closed-loop process costs more to run than an open-loop one, and certified wood costs more than uncertified pulp. Rayon's cheaper chemistry is the reason it costs less, and the reason it weakens when wet while Tencel keeps about 85 percent of its dry strength.
Is bamboo fabric the same as Tencel?
No. Most bamboo fabric is bamboo viscose, which is rayon made from bamboo pulp through the same open-loop carbon disulfide process. The FTC has sued retailers since 2010 for marketing it as bamboo, because the bamboo is gone by the time the fibre exists.