Date of this Version
Matzen, Michael. (2015). Sustainability Assessment for Energy Systems and Chemical Process Industries (Masters Thesis). University of Nebraska - Lincoln
Sustainability has become an important factor in the chemical process and energy industries with a strong drive for process improvements towards more environmentally conscious solutions. However, there are many ways of defining sustainability and even more ways of trying to determine how sustainable a process is. This work looks into applying a conjunction of tools including; process simulation, multi-criteria decision matrices and life-cycle assessment to more quantitatively determine sustainability metrics. We have applied these tools for the production of electricity, methanol and dimethyl ether. A novel method of electricity production, in chemical looping combustion (CLC), was used that inherently involves carbon dioxide capture. Experimental work was conducted for two different oxygen carriers, CaSO4 and CuO, using thermogravimetric analysis (TGA). Process simulations were developed for both coal and natural gas (NG) feedstocks to produce power and heat. Sustainability metrics were developed based on simulated data showing electricity prices of 23.7 ¢/kWhr (NG) and 7.8 ¢/kWhr (coal) while reducing CO2 emissions 0.38 (NG) and 3.38 (coal) metric ton/MWhr electricity. Renewable methanol production was also simulated in Aspen Plus. This process used wind based electrolytic hydrogen and captured CO2 as feedstocks. This work presents a multi-criteria decision matrix for the inclusion of sustainability metrics alongside economic indicators in feasibility analysis. A comparison of renewable methanol to NG based methanol using this matrix shows that the renewable process is feasible. We continued this work to conduct a full (cradle-to-grave) life-cycle assessment of alternative fuels based on this renewable methanol and its conversion to dimethyl ether. Using renewable methanol as a fuel reduces greenhouse gas emissions 86% and fossil fuel use by 91% compared to conventional gasoline. Using dimethyl ether reduces greenhouse gas emissions 80% and fossil fuel use 81% when compared to ultra-low sulfur diesel. This whole work focuses on developing sustainability metrics helps identify a quantified measure of sustainability that can be used along economic indicators in a multi-criteria decision matrix for a better and comprehensive feasibility evaluation of energy systems and chemical processes.
Advisor: Yaşar Demirel