Natural fibers in carpeting are generally wool, cotton, sisal, sea grass, jute, hemp, coir and rush. There are several types of wool fibers. Long, coarse guard hairs protect the softer, finer fibers on a sheep’s back.

Their short, coarse, brittle fibers are called kemp. Kemp accepts dye very reluctantly. The industry adds kemp to some of its yarns to give them a distinctive texture and appearance. A good carpet yarn will have some crimpy (wavy) fibers for springiness and elasticity which helps resist crushing from the weight of furniture.
Wool right off the sheep is cleaned and carbonized (soaked in dilute sulfuric acid and heated). The less carbonization, the stronger and more durable the carpet yarn. Wool is a protein fiber, its outer layer a thin water-repellent coating that resists the absorption of water, allowing liquid spills to bead up. Its yarns trap air, giving good insulating qualities. Wool is naturally highly fire resistant. Wool fiber carpets are best used in dry, well-ventilated places and should not be allowed to remain damp if they do get wet.
Wool/hemp blend carpeting is available with added natural mold and mildew resistance. The natural resilience of wool offers durability that exceeds most synthetics. The hemp adds strength, pest resistance qualities and UV resistance.
Grass-based carpeting options derive their strength from the weave and are naturally anti-static. They are affordable, versatile, easy to install and are resourced from replenishable, sustainable resources.
Jute is the softest grass-based carpet option. Jute can withstand a lot of abrasion. It is resistant to mildew and mold; however, the fiber is absorbent and deteriorates when consistently exposed to moisture and sunlight. Jute relaxes with use, so edges must be beveled away form the seam.
Seagrass is durable and stain resistant, but cannot be dyed. Its advantage is the more accepting a material is of dyes, the more likely it is to stain. When it is woven into a carpet, the result is a highly spill-resistant, durable, resilient floor covering that is comfortable under foot.
Sisal fiber comes from the renewable agave plant and is generally harvested every 7 years. No pesticides or chemical fertilizers are used in sisal production. It can be woven into different patterns and accepts dyes. It can be a little rough underfoot, but less so when combined with other fibers. Sisal carpets are naturally sound-absorbing and durable. They are also naturally insulating and difficult to ignite. Like most plant fibers, however, sisal absorbs moisture readily, therefore we recommend that these materials be used only indoors, in dry areas.
Linen is spun from the fibers of the flax plant. Linen yarns are strong and durable, resistant to wear and abrasion, yet are lustrous, flexible, and pleasant to the touch.
Coir fiber comes from the fibrous husk that encases a coconut. Its natural colors range from tan to golden brown to reddish-brown. To achieve other colors, the fibers are bleached and dyed. Coir is tough, does not pill, can withstand a great deal of abrasion, is highly rot resistant, and is unfriendly to insects. It is naturally insulating and difficult to ignite. Coir has an ability to tolerate submersion in water for months without disintegrating, making it a good choice for outdoors and areas subject to water use.
LEED points: MR Credit 6 for rapidly renewable materials.