UC Santa Barbara

The decarbonization of energy system plays a fundamental role in global climate change mitigation efforts, and it entails unprecedented infrastructural transformations across the whole energy supply chain and the end uses as well as large scale deployment of emerging low-carbon technologies. In addition to the carbon mitigation potential, it is also critical to comprehensively assess other sustainability dimensions of the decarbonization actions. Techno-economic analysis (TEA) and life cycle assessment (LCA) are two main methods that are used to quantify the economic and environmental performances for energy system technologies, respectively. However, applying these methods at technology-level is limited to capture the dynamic system contexts and their effect on the technology performances. The main contribution and novelty of this dissertation is that it evaluated the economic and/or environmental implications of decarbonization actions in the energy system by linking the relevant methods with scenario analysis and/or system modeling approaches. This methodology integration makes it possible to capture the effects of system interaction and evolution on the performance of decarbonization actions. A transition to energy-efficient lighting technologies (e.g., fluorescent and light-emitting diode (LED) lightbulbs) assist climate change mitigation by reducing energy consumption. In Chapter II, I studied the uses and recycling of critical rare earth oxides (REOs) in the efficient lighting technologies. The demand for REOs in the lighting sector shows a rapid increase during 1990 and 2014 driven by the global adoption of fluorescent lightbulbs, but this increasing trend decreases after the peak as more efficient LED lightbulbs (that requires significant less REO consumption than fluorescent lightbulbs) penetrated the market and replaced fluorescent lightbulbs. The REO recycling from end-of-life lighting technologies are not economically feasible under 2018 REO prices, even though economy of scale can reduce recycling cost by two third as plant capacity increases from 100 t/yr to 1,500 t/yr, highlighting that the improvement of REO recycling rate may need higher REO prices or commensurate policy interventions. In Chapter III, I quantified the total system cost of the U.S. electric power system under different decarbonization scenarios based on the capacity expansion and dispatch outputs from an electricity system optimization model. I found pursuing zero CO2 emission by replacing fossil fuel with renewable and other low-carbon energy sources would incur $335–$494 billion additional cost (5% discount rate, 2020 US$) to the U.S. electricity system during 2020–2050 (compared to a reference scenario). Additionally, the marginal costs of mitigating the last few percent CO2 emission from the U.S. electricity system could exceed the costs of some carbon dioxide removal (CDR) solutions, such as bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS), indicating their potential opportunity to decarbonize the electricity system. In Chapter IV, I evaluated the prospective environmental performance of DACCS which is a CDR solution that deliberatrely removes carbon dioxide (CO2) from atmosphere. I found decarbonizing the electricity sector leads to environmental trade-offs for DACCS by increasing its terrestrial ecotoxicity and metal depletion levels both by an average of 56% from 2020 to 2100, but these increases can be reduced by improving the material and energy use efficiencies of DACCS as it scales up. Also, DACCS deployment aids the achievement of long-term climate targets, its environmental and climate performance however depend on sectoral mitigation actions, and thus DACCS deployment should not suggest a relaxation of sectoral decarbonization targets. This dissertation provides robust and reliable insights for the low-carbon transition in energy system by evaluating the economic and environmental performances of decarbonization actions in dynamic system contexts. Decarbonization actions in the energy system could lead to economic and environmental trade-offs which should be carefully studied and considered in policy decisions. Future studies and policies may also rely on multi-criterion decision analysis to decide how to implement a variaty of decarbonization actions in energy system based on the optimization of different sustainability dimensions.