"Sustainable t-shirt" almost always means either organic cotton or recycled polyester, and the two get lumped together as equally good options. They solve different problems, with different tradeoffs, and picking between them depends on what you actually care about reducing.
Organic Cotton: Water and Land, Not Zero-Impact
Organic cotton farming avoids synthetic pesticides and fertilizers, and organic cotton generally uses less water than conventional cotton per unit grown, largely due to healthier soil retaining moisture better. It's still a water- and land-intensive crop overall — "organic" reduces cotton's footprint, it doesn't eliminate it. At end of life, an organic cotton shirt is biodegradable, breaking down naturally rather than persisting in a landfill.
Recycled Polyester: Diverted Waste, Permanent Material
Recycled polyester is typically made from post-consumer PET plastic (often bottles), diverting material that would otherwise be landfilled or incinerated, and it requires meaningfully less energy to produce than virgin polyester. The tradeoff: it sheds microplastic fibers with every wash cycle, contributing to the microplastic pollution found throughout waterways, and it never biodegrades — a recycled polyester shirt is still plastic at end of life, just previously-used plastic.
The Honest Comparison
| Impact | Organic Cotton | Recycled Polyester |
|---|---|---|
| Growing/production footprint | Lower than conventional cotton | Lower than virgin polyester |
| Microplastic shedding | None | Yes, every wash |
| End-of-life | Biodegradable | Persists indefinitely |
| Upstream benefit | No synthetic pesticides | Diverts existing plastic waste |
Verdict
There's no clean winner. If microplastic pollution and end-of-life biodegradability matter most to you, organic cotton is the better choice. If you're prioritizing diverting existing plastic waste out of the ocean/landfill stream, recycled polyester does that job that organic cotton can't. A closet with both, chosen deliberately by garment type, is a more honest approach than treating either as a universal answer.
