Undesirable input–output two-phase DEA model in an environmental performance audit

Widespread environmental concern provides an opportunity for the development of environmental auditing. This study aims to analyze ideas that address evaluation difficulties in an environmental performance audit and to promote the application of environmental performance audit in energy saving and emission reduction toward a high-end direction. An improved data envelopment analysis (DEA) model is applied in the environmental performance audit by data translation and the transformation method. With benchmark management considered, a two-phase DEA model algorithm is proposed to solve restricted inputs and outputs for pollutants or wastes as well as to overcome the relative efficiency of defects in traditional DEA evaluation. In the case study of a domestic sewage treatment plant, the model is found to improve the flexibility and effectiveness of the application.