Solid wastes in brewing process: A review

A large amount of agro-industrial waste is produced annually around the world from the beneficiated agricultural products or in food industrialization. The disposal of these residues in the environment results in a lot of inconvenience to the ecosystem, due to its significant nutritional value and high concentration of organic compounds that confers a high biochemical oxygen demand to the waste’s degradation. In this context, brewing industry is among these activities, which includes in its production stages the processing and fermentation of vegetable feedstock, such as barley malt and other grains, and hops, generating several by-products. Many factors, such as environmental policies, possible scarcity of non-renewable sources, and problems related to the improper use of renewable raw materials, leads to the development of new processes that could generate less waste or reused those produced in order to add greater value to the residue. This article presents a review of the solid wastes in brewing industry, which are the brewer spent grain, the hot trub, the residual yeast and the diatomaceous earth, describing how they are obtained in the brewery process, their characterization and chemical composition, and the potential applications in bioprocesses technologies. The main fraction common to all revised waste is the protein fraction, in addition to various constituents of interest, such as minerals, carbohydrates and phenolic compounds. The main current applications are in the area of ​​animal feed and human nutrition. Key words: brewery wastes, brewer spent grain, trub, residual yeast, diatomaceous earth.