Materials Balance

Materials balance says that material inputs to every process must balance with the outputs. This is equivalent to the mass conservation law that says that the weight of materials going into a process must equal the material outputs, including wastes.

This concept is a useful analytical tool for process analysis from the plant level to the global level. Materials balance can be used in life cycle analyses to determine whether styrofoam or paper plates are more environmentally friendly by comparing the amount of inputs are needed to produce equivalent outputs.

The materials balance principle is also useful when looking at world consumption of goods. With this principle we are able to quantify what world waste residuals are by knowing the amount of inputs and knowing that only a small percentage of the total mass of materials processed is embodied in a product that lasts for more than a decade.

In systems thinking materials balance is used in the materials flow segment to quantify and show the roots to the flow of materials.(Eblen and Eblen, 1994, p. 436)

Compiled by

Keith Cunningham kc3@cec.wustl.edu Last updated 11/12/94.