A thermodynamic framework for ecologically conscious process systems engineering

Making process systems engineering decisions that are ecologically conscious requires analysis of both industrial and ecological processes. Traditional methods in process engineering usually fall short of meeting this requirement due to considering the environment as secondary to economic objectives. Life cycle assessment and design methods have broadened the scope of traditional methods by considering the environmental impact in the entire life cycle of a product or process. These methods focus primarily on the environmental impact of emissions and ignore the contribution of ecological products and services. This paper presents a thermodynamic approach for including the input from both ecological and economic resources, and for analyzing industrial and ecological processes together. This approach is based on the fact that growth and sustenance of both industrial and ecological processes are limited by the available energy and its conversion to useful work. Thus, the embodied energy (emergy), that is, the energy used directly or indirectly to make a product or service is a measure of ecological cost. Emergy analysis of industrial and ecological processes provides insight into the environmental performance and sustainability of the industrial process or product. Emergy-based life cycle assessment is developed to combine the benefits of both methods. The proposed framework is broadly applicable and is illustrated by the emergy based life cycle assessment of soy bean growth. © 2000 Elsevier Science Ltd. All rights reserved.