Energy Circulation

Global warming caused by raising concentration of atmospheric Greenhouse-gas (GHG) is a greatest challenge over the world. Vigorous efforts to cut down the GHG emissions are being implemented everywhere. Water infrastructures including water treatment plant (WTP), wastewater treatment plant (WWTP), sewer pipeline, and rainwater management system are one of the most significant infrastructures emitting considerable amount of GHG emissions by consuming gigantic amount of electricity for operation and raw materials for construction. Also, huge amount of GHG emissions are caused by chemical or biological reactions during treatment and conveyance processes. Therefore, mapping system relationship between unit processes and estimating the amount of GHG emissions should be essentially conducted to improve energy and resource efficiency of systems.

To achieve sustainable energy and resource circulation for water infrastructures, we have developed advanced life cycle assessment (LCA) model and analyzed the system to suggest a potential alternative. Firstly, GHG emissions are quantitatively calculated to understand accurate situation and identify a key emission source by applying LCA. This is a systematic methodology to evaluate environmental impacts between alternatives by considering from raw material acquisition to disposal stage. The advanced LCA model developed by our research can estimate more accurate GHG emissions by considering an effect of biochemical reactions and detail operation conditions of unit processes than previous models do. Secondly, feasible strategies for mitigating GHG emissions can be suggested by considering a mathematical way such as sensitivity analysis or optimization theory. Sensitivity analysis can determine the most influential operation variable on electricity consumption in unit processes and suggest the tactics to bring less GHG emitting system. Also, by applying optimization theory, we can compare the mitigation effects among optimal and current life cycle scenarios and propose the direction to reduce environmental loads.