What is the materials balance model?

the materials balance model is an environmental Economics model which explains a relationship between the environment (the starting point) and how we take its raw materials into a productions process. In the aftermath of production, the biproducts can become residuals that are discharged, or residuals that are recycled to be used in the cycle again. The goods from production are subsequently used by consumers who produce residuals as well, that are both discharged or recycled (re-entering the consumer tract of the model).