Draffs are an agricultural byproduct that are left over after the milling process of grains such as wheat, barley, and oat. Synonyms for draffs include brewery waste, grain residue, and spent grain. Brewery waste is the leftover byproduct from the brewing process and is a similar product to draffs. Grain residue refers to the leftover materials from the harvesting and cleaning of grain. Spent grain is a term often used to refer to the leftover mash from the brewing process, which includes draffs as well as other materials. These synonyms are important for farmers, brewers, and other industries to be aware of as they deal with agricultural waste management.