CBE PhD Dissertation Defense | “Process Development and Modeling for the Advancement of Direct Air Capture Technologies”

Abstract: 

“As the catastrophic effects of climate change are felt throughout our global society, we must take immediate action. A portfolio of climate solutions must include both deep and robust decarbonization, and systems to remove carbon dioxide directly from the atmosphere. One promising suite of carbon removal technologies is Direct Air Capture (DAC). DAC refers to engineered systems that pull CO2 from air, capturing it in a near-pure form. The captured CO2 can be stored geologically (resulting in a reduction of atmospheric CO2 concentrations), or otherwise utilized. This Dissertation focuses on development and deployment of DAC technologies first by exploring the current DAC landscape, then by proposing a novel DAC process using earth-abundant minerals.

The current landscape of DAC includes two main approaches: solid sorbent and liquid solvent. Each DAC approach has advantages and challenges, including energy usage, specialty chemical demand, and land area requirements. Here, each approach is outlined, and suggestions are provided to accelerate industrial deployment. Additionally, the effect of different dedicated energy infrastructure to power solvent-based DAC is evaluated, including both fossil and renewable energy resources and quantifying the effect of energy-related emissions on the amount of carbon net removed from air. A technoeconomic tool is also presented which allows for a high-level cost estimate of DAC based on available information. The tool can be utilized by investors to evaluate key aspects of DAC technologies and determine which innovations result in significant cost reductions.

An ambient oxide looping process is proposed as a novel approach to DAC. The process uses earth-abundant minerals (limestone, magnesite) to produce reactive oxides (calcium oxide, magnesium oxide) that react with the CO2 in air. Investigation into the economics of the process indicates it could be less expensive per ton of CO2 removed than other DAC technologies. To understand the process viability, a series of experiments characterize industrially available calcium and magnesium oxide and hydroxide feedstocks. These experiments probe the physical properties of these materials and different aspects of engineering optimization, including material depth and rate enhancement as a function of both relative humidity and direct water addition to the system. “