Material quantities, as they  pass  through  processing  operations,  can  be described by material balances. Such balances are statements on the conservation of mass. Similarly, energy  quantities can be described by energy  balances, which  are  statements on the conservation of energy. If there is no accumulation, what goes into a process must come out. This is true for batch operation. It is equally true for continuous operation over any chosen time interval.

Material and energy balances are very important in an industry. Material balances are fundamental  to  the  control  of  processing,  particularly  in  the  control  of  yields  of  the   products. The first  material balances are determined in the exploratory stages of a new process, improved during pilot plant experiments when the process is being planned and   tested, checked out when the plant is commissioned and then refined and maintained as a   control instrument as production continues. When any changes occur in the process, the   material balances need to be determined again. The increasing cost of energy has caused the industries to examine means of reducing   energy consumption in processing. Energy balances are used in the examination of the various stages of a process, over the whole process and even  extending over the total production system from the raw material to the finished product.

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