Two engineers, Eben Bayer and Gavin McIntyre, at Rensselaer Polytechnic Institute in New York State, when studying the properties of different cultures of mushrooms, noticed that by manipulating the growth environment, they were able to shape the material’s strength, flexibility and temperature tolerance. This led to the development of a product which they called "Greensulate".

Greensulate is a renewable and biodegradable organic material that can be used for thermal insulation, fire insulation and as a substitute for the polystyrene used in packaging and many other applications. Polystyrene, on the other hand, is made from non-renewable petrochemicals; it is not biodegradable and takes up large amounts of landfill space where it can last for thousands of years.

Greensulate is made of very cheap agricultural by-products of rice, buckwheat and cotton seed. This is used as a base for the growth of a type of mushroom called pleurotus ostreatus. The mushroom’s mycelium (the mass of threadlike filaments from which the fruiting body of the mushroom grows) binds the agricultural by-products together. The whole is put into moulds in a dark environment and left to grow for up to two weeks. When it has filled the mould, its is dried to prevent further growth and avoid moss or fungus allergy due to exposure to the product.