Wool is a natural and renewable resource. Sheep grow wool naturally and continuously - it is part of their biological anatomy. If wool is discarded, it will naturally decompose into the soil in a few months or years, slowly returning valuable nutrients to the earth. Synthetic fibers, on the other hand, can break down extremely slowly and contribute significantly to the world's overflowing landfills. Wool also degrades in a marine environment and does not contribute to microplastic pollution. Unlike synthetic textile microfibers (microplastics), which accumulate in marine and terrestrial environments, where they cause ecological damage.
What is the difference between microfibers and microplastics?Microfibers: Minuscule fibers with a linear mass of less than 1 decigram. All fibers lose microfibers, but depending on the materials from which they are made, some microfibers may degrade while others do not. Microfibers made from natural fibers such as wool will break down while microfibers made from synthetic fibers will not. Microplastics: Microfibers made from synthetic materials such as acrylic, polypropylene, polyester and polyamide with a diameter of less than 5mm (0.2 inches). Microplastics are not biodegradable and are created by the disposal and decomposition of consumer products and industrial wastes.
How does wool biodegrade?
All materials of animal and plant origin have a certain biodegradability, meaning they can be broken down by the work of living organisms, such as fungi and bacteria. Wool is composed of the natural protein keratin, which is similar to the protein that builds human hair. When keratin is broken down naturally by microorganisms, the products pose no environmental risk.
Wool breaks down quickly
Wool easily biodegrades in as little as three to four months, but the rate can vary depending on the soil, climate and properties of the wool. This returns essential elements such as nitrogen, sulfur and carbon to the soil, where they can be taken up by growing plants. Some studies have even shown faster decomposition after just four weeks buried in the soil. When wool biodegrades, carbon is also returned to the soil as part of the natural carbon cycle. Research has shown that processing treatments such as dyeing and anti-shrinkage treatment can affect the degradation rate of wool in the soil. For example, dyeing can cause wool fabrics to degrade at a slower rate initially, but this effect usually lasts only a few weeks. On the other hand, recent research has shown that the Chlorine-Hercosett anti-shrinkage treatment applied to wool (making wool clothing suitable for machine washing) can accelerate biodegradation. It does this by removing part of the cuticle of the fiber (the armor plate), making it more susceptible to microbial degradation.
Wool is easily biodegraded in warm and humid conditions
When drained, if wool is warm and moist or buried in the ground, fungi and bacteria develop that produce enzymes that break down wool. On the other hand, thanks to keratin's unique chemical structure and wool's tough, water-repellent outer membrane, clean and dry wool fibers do not break down easily. This makes wool products resistant and long-lasting under normal conditions.
Wool returns essential nutrients to the earth
When buried in the soil, wool becomes a slow release fertilizer that provides nutrients for uptake and growth by other organisms. Some have even used wool fertilizer to promote herb and vegetable growth. This is known as natural closed loop recycling; restoring the initial inputs of soil and grass. Other beneficial effects of adding wool to soils include increased water holding capacity, improved water infiltration, soil ventilation and reduced erosion. Finely chopped wool floor coverings used as fertilizer increased the dry matter yield of grass growth by 24% to 82%.
Wool does not contribute to waste volumes and microplastic pollution
Wool fibers biodegrade naturally over a relatively short period of time in soils and marine systems and therefore do not accumulate in waste and oceans. Results from a 2020 Ag Research study show this and further, no evidence was found that the polyamide resin used as part of the machine washable wool treatment causes microplastic pollution. In contrast, synthetic textiles do not biodegrade and persist for many decades, crumbling into small fragments. These fragments, commonly known as microplastics, accumulate in aquatic environments and waste repositories where they have negative effects on ecosystems when ingested by organisms. A single polyester fleece garment can produce more than 1,900 fibers per wash. Ingestion harms organisms, sometimes to the point of death by starvation because plastic replaces food in the stomach. Once in the food chain, microplastics can also potentially affect human health through consumption of seafood. Microplastics have also been found in drinking water, both bottled and tap water.