A new method for analysing environmental efficiency, based on the materials balance, is proposed. With this method, an environmental allocative efficiency measure can be defined analogously to the more commonly used economic allocative efficiency. Nutrient surplus in pig fattening, a typical balance indicator, is used to illustrate the concept in a two input - one output case. The materials balance based efficiency analysis is elaborated using data envelopment analysis (DEA). Results are compared with those of more common, merely input or output oriented DEA approaches. A main conclusion is that, ignoring the balance feature of environmental issues such as nutrient surplus might be a main reason why traditional integral analyses of economic and environmental efficiency yield contradictory conclusions.