Life cycle assessment of alternatives for waste-solvent valorization: batch and continuous distillation vs incineration

摘要

Purpose The goal and scope of this research is focused on the application of life cycle assessment (LCA) to evaluate two alternatives (batch and continuous distillation and incineration with energy recovery) for the treatment of four waste-solvent mixtures typically produced in the chemical industry: acetonitrile-toluene, acetonitrile-toluene-tetrahy-drofuran (THF), ethyl acetate-water and methanol-THF, with several compositions in order to determine the most appropriate technology depending on the characteristics of the mixture. Materials and methods Ecosolvent® v. 1.0.1 software is used to perform the LCA, considering two scenarios and the following methods of impact assessment: Eco-indicator 99, cumulative energy demand, method of ecological scarcity (UBP'97), global warming potential and CO_2 balances. Results and discussion Results show that distillation gives more environmental credits for the recovery of the most concentrated compound in acetonitrile-toluene mixtures. However, when THF is present in the waste solvent even in small quantities, it has to be recovered due to the high impact associated to its manufacture. Regarding the mixture ethyl acetate-water, distillation takes advantage at concentrations of ethyl acetate higher than 50 wt%, and for the mixture methanol-THF, recovery of methanol is not advantageous from an environmental point of view, but the recovery of THF is clearly necessary to decrease the total impact. Conclusions From this study, it can be concluded that those compounds that yield a great environmental burden during the production step should be always recovered in order to minimize the total impact, even if they represent the minor concentration in the mixture. In case that similar impact is produced during the solvent production, the major compound in the mixture should be the target for recovery.