Emergy and Sustainability

This article presents emergy evaluation and its application to ecosystems and territorial systems. The emergy approach is an environmental accounting methodology that can be used to assess natural inflows and services within a system. This ecological indicator was inspired by the food chain and the observations that energy quality increases along the chain while energy content decreases. Emergy analysis is able to differentiate between the various units (processes) of an ecosystem. It highlights processes that are sustained by low-quality energy and processes that need high-quality fluxes. The method is an embodied energy analysis that uses solar energy as reference. By evaluating natural resources on a common basis, emergy analysis has proved useful at the interface between human and natural systems and for assessing the impact of human activity on ecosystems. Based on a rigorous algebra, emergy evaluation provides indicators to measure sustainability.