The production of ethanol also generates liquid effluent, which may ren­der a potential pollution problem or a concern of environmental stress on water systems. About nine liters of liquid effluent are generated for each liter of ethanol produced, which varies depending on the specific process adopted. Some of the liquid effluent may be recycled. Effluent can have a high level of biochemical oxygen demand (BOD), which is a measure of organic water pollution potential, and it is also acidic. Therefore, the liquid effluent must be treated before being discharged into the water stream. Specific treatment requirements depend on both feedstock quality (and type) as well as local pollution control regulations. Due to the acidity of the effluent, precautions and care must also be taken if the effluent is directly spread over fields [18].