Improved emergy indices for the evaluation of industrial systems incorporating waste management

Emergy analysis is able to account for ecosystems' contribution to industrial activity. Accordingly, it is an ecologically conscious tool useful for assessing the environmental impact and sustainability of industrial systems. The emergy-based approach requires proper system boundary definitions and uses several standard indices. In this article some perspectives on the deficiencies of three standard emergy indicators - environmental loading ratio (ELR), emergy yield ratio (EYR) and emergy index of sustainability (EIS) - when applied to industrial systems involving waste management are put forward and suggestions for overcoming them given. In addition, in order to account for the impact of waste emissions on the environment, a simple impact amplification factor is proposed for inclusion in the improved emergy indicators. To demonstrate their usefulness and highlight their superiority over standard indices, the improved emergy indicators are used to evaluate the interaction between a commercial polyethylene production process incorporating waste management and its surrounding environment.