The Activewear Sustainability Audit: Recycled vs Natural Fibres

In 2026, "Recycled Polyester" has become the standard for "sustainable" activewear. But is turning plastic bottles into leggings a real solution, or just a detour to the same landfill?

At Estroni, we believe sustainability is measured by the end of a garment's life, not just its beginning. When you compare the lifecycle of a recycled synthetic fiber to a natural protein fiber like Merino, the "Performance Gap" becomes a "Sustainability Gap."

This audit breaks down the data on biodegradation, microplastics, and the reality of the textile circular economy.

1. The "Forever" Problem: Biodegradation Rates

The primary issue with recycled polyester (rPET) is that it is still plastic. Recycled or not, the molecular structure of the fiber is designed to last for centuries.

The Data: Research published in Environmental Science & Technology confirms that synthetic fibers can take up to 200+ years to decompose in a landfill environment. During this time, they leach chemicals into the soil.

The Merino Difference: As a natural protein, Merino wool is 100% biodegradable. In the right conditions (soil or marine environments), a Merino garment can almost completely biodegrade in less than 12 months, releasing essential nutrients like nitrogen back into the earth.

2. The Microplastic Loop

One of the most significant data points in textile science is "shedding." Every time you wash your activewear, it releases tiny filaments into the water system.

The Study: A study by the International Wool Textile Organisation (IWTO) found that while all clothes shed, the impact is vastly different:

Recycled Polyester: Sheds microplastics that are non-biodegradable. These enter the food chain and have been detected in human blood and lung tissue.
Estroni (Merino): Also sheds fibers, but these "micro-fibers" are biodegradable protein. They break down in aquatic environments and do not contribute to the global microplastic crisis.

3. Energy & Chemicals: The Hidden Cost

Recycling plastic into fabric is an energy-intensive chemical process. It often requires high heat and chemical "compatibilizers" to ensure the recycled plastic can be spun into a fine yarn.

The "Downcycling" Trap: Most recycled polyester leggings cannot be recycled a second time. They are at the end of their usable life the moment they are made.
Estroni’s Renewable Cycle: Merino is grown using solar energy (grass), water, and sheep. It is a renewable resource that grows back every year, requiring significantly lower chemical inputs than the production or recycling of synthetics.

Audit Summary: Estroni vs. Recycled Synthetics

Audit Metric	Estroni Merino	Recycled Polyester (rPET)
Source	Renewable (Natural Protein)	Petroleum-based (Plastic)
Biodegradability	< 1 Year (Soil/Marine)	200+ Years
Microplastic Impact	Zero (Biodegradable fibers)	High (Permanent pollutants)
End-of-Life	Nutrient for the earth	Landfill / Incineration