Odor control for livestock and compost facilities has focused on manure handling and treatment during storage and land application, however, large amount of malodorous air is emitted and it is one of main sources of malodour in livestock farming. Biological treatment or biodegradation involves converting an organic contaminant to carbon dioxide and water using natural bacteria. Biofiltration is an effective air pollution control technology that uses microorganisms to breakdown gaseous contaminants and produce innocuous end products. Investment and operating costs on the biofiltration are lower than for thermal and chemical oxidation processes. This paper is intended to provide an overview of basic design and operating criteria for biofilters to control odors from livestock and compost facilities.