We present a new methodology to evaluate, under uncertainty, the waste treatment options for a new product in an existing facility, considering economic and environmental objectives. The methodology highlights potential treatment problems, forecasts the required operations, and estimates costs and environmental impact. The new procedure includes a rigorous evaluation of secondary streams. The uncertainty of the waste stream composition, cost factors, and separation efficiencies are taken into consideration. The new procedure accounts for possible interaction and synergy between several waste streams. The option of stream mixing is considered to increase the efficiency of central recovery operations or to achieve dilution of critical streams in the final treatment operations, e.g., the sewage treatment plant, and, hence, to reduce the need for expensive pretreatments such as stripping. The most-efficient treatment paths for an original waste stream might be composed of complex combinations of the aforementioned options; e.g., some part of a stream is recovered directly in the production building, while the remainder is mixed with another stream for recovery in a central distillation, before being sent along with two additional streams to incineration. For each waste stream, a list of such combinations and the resulting economic and environmental assessments is obtained.