South West Trading Company says
SOYSILK® brand fiber is made from the residue of soybeans from tofu manufacturing. This process is 100-percent natural and free of any petrochemicals, making it an extremely environmentally friendly product. Soy is a completely renewable resource – coming from the earth and being wholly biodegradable. As early as the 1940s, textile experts dreamed of a fiber made from soy. (In fact, Henry Ford had a suit made of soy as an early prototype.) SOYSILK® brand fiber offers superior moisture absorption and ventilation properties along with beautiful draping, softness and warmth.It took two weeks to knit this up and I am very pleased with the cowl. And it is environmentally green as it contains natural anti-bacterial agents which can restrain the growth of certain types of bacteria and is therefore considered a very sanitary fiber.
It has the softness and smoothness of cashmere but isn’t hazardous to the environment. The fiber also has the same moisture absorption as cotton but with better moisture transmission, making it more comfortable and sanitary (from here).