Schematic representation of multi-step recycling. The number of steps in this case is 4. The initial steel is shown as “INITIAL” and the amount available at each step decreases with time (recycling rate = 80%). At each recycling step, some steel is not recycled because of dissipation to the environment. Material dissipated at the 1st recycling step is shown as “D1”, at the 2nd step “D2”, 3rd step “D3” and 4th step “D4”.