Environmentally preferable treatment options for industrial waste solvent management -: A case study of a toluene containing waste solvent

A major environmental issue concerning waste solvent management in the chemical industry is the question whether waste solvents should be incinerated or recovered. In this study we evaluated the incineration and the distillation of a toluene containing waste solvent mixture with respect to its environmentally preferable treatment options. To this end, we performed life-cycle assessments (LCAs) of two case studies, an LCA of a waste solvent incineration plant and an LCA of a batch distillation column. Subsequently, we set up a simplified evaluation procedure for the treatment options, which allowed for an evaluation based on three different impact assessment methods, i.e. Swiss Ecopoints, Eco-Indicator 99 and primary energy demand. Since the evaluation of waste solvent incineration and distillation was strongly influenced by credits for avoided products such as steam and electricity, different scenarios for the energy supply were considered in the procedure. The evaluation results depended on the impact assessment method chosen and some pertinent properties of the waste solvent mixture such as the high enthalpy of combustion. If the evaluation was based on Eco-indicator 99 or primary energy demand, distillation was the preferable treatment option due to hi-h credits for recovered non-renewable resources. In contrast, if emissions to air and water are considered more important, such as in the Swiss Ecopoints method, incineration scored better due to higher credits calculated for the avoided energy production.