Technical and environmental efficiency of a two-stage production and abatement system

In this paper, a network data envelopment analysis system that considers a production stage followed by an abatement stage is studied. Two DEA models are proposed for assessing, respectively, the technical and the environmental efficiency of the system. The technical efficiency model computes a network slacks‐based inefficiency measure. In the case of the environmental efficiency model the reduction in the pollutants emissions can be weighted according to their environmental impact or to their allowance costs, thus allowing inputs as well as pollutants substitution. An allocative efficiency score can also be computed comparing the technical efficient projection with that of the environmental efficiency model. A key feature of the proposed approach is that it assumes that any inputs, outputs or intermediate products that contain the pollutants of interest are not freely disposable. Assuming otherwise would violate the materials balance principle. The proposed approach has been applied to a dataset involving 23 coal‐fired power plants and a single pollutant. The results show that the technical efficiency model estimates maximum input reductions and output increases, which brings about significant emissions reductions. Those reductions are, however, smaller than those than can be achieved when environmental efficiency is the goal.