Sensitivity analysis of the emergy flows at the solar salt production process in Slovenia

Abstract

Upgrade of the emergy analysis of Sečovlje saltpans [Babič, J., 2005. Emergy analysis of the salt production process at the Sečovlje saltpans, Slovenia. In: Proceedings of the Third Biennial Emergy Analysis Research Conference, January 29–31, 2004. The Center for Environmental Policy, Gainesville, FL] was performed with STELLA programming language. STELLA model of the solar salt production process was constructed to simulate emergy flows and emergy indices. Sensitivity analysis of state variables with regard to various emergy indices was also performed. We compared several process scenarios as well as the process behavior under different environmental and economic conditions. The model structure enables adding new state variables in order to obtain better control over emergy flows within the model and between the model and its environment. Results show that evaporated water contributes the highest identified environmental renewable emergy inflow to the area. Precipitations themselves have very negative effect on actual salt production due to the dilution of concentrated brine with rainwater. However, human labor, as it is driven mostly by nonrenewable emergy, contributes the highest nonrenewable emergy inflow. The general trend of decreasing percentage of renewable emergy in human work as well as the need for additional inputs of nonrenewable emergy aimed at reducing labor demand, limits the possibilities to achieve a higher sustainability and a lower environmental loading of the investigated production process. The paper compares the effects of different process modifications and the effect of changing meteorological conditions to the indicators of environmental loading and degree of sustainability.