Walnut shell powder Yogisgift Walnut shell powder is a byproduct of walnut oil production that has a wide range of uses. It is made from the shells of the English Walnut and has a coarse texture. Walnut shell powder can be used as a natural abrasive in products such as toothpaste, facial cleansers, and exfoliants. It is also used as a filtration medium for water treatment, and in oil drilling and production.