The first set of constraints (5) ensures that all wastes generated
are included in the system. All wastes originating from generators
must be sent to hazardous waste facilities with compatible tech-
nologies. The second set of constraints (6e12; the flow balance
constraints), demands that total amount of hazardous residues
(that is, the portion of waste remaining after processing) equals the
amount of waste entering the facility times the mass reduction
ratios. The third set of constraints (13), which ensures that wastes
are sent to a node only if there is a facility established, makes use of
binary variables. For this constraint set, no upper capacities are
assigned to facilities. Last, the numbers of facilities are para-
metrically set (13).