ABSTRACT
A standard tool in process engineering is the use of elemental balances. According to this method, the balances are written down for each separate chemical element. For bioreactor design, they provide useful information about the flows through and production in the apparatus. For instance, at a given sugar feed rate to a fermenter, growth and maintenance of the microorganisms determine the ammonia consumption rate. Because accumulation should be prevented, the ammonia feed rate to the fermenter should have the same value. Balances can provide the relation between sugar and ammonia feed rate. In the same way the total mass of the fermenter and the concentrations at the end of the fermentation can be calculated. These data can be used to calculate the fermenter volume that is required and can be used as input variables for downstream processing design. In the design of a new production plant balances are the basis for the whole flow sheet. Finally, it should be possible to provide design criteria based on very limited input data such as: "This amount of BOD should be removed," or "That amount of product should be produced in a day." This chapter will deal with the principles of balances for bioreactor design.
