Synthesis and Regeneration of Sustainable CaO Sorbents from Chicken Eggshells for Enhanced Carbon Dioxide Capture

Eggshell waste, which contains 95% calcium carbonate (CaCO3), presents itself as an inexpensive calcium-based sorbent for removal of carbon dioxide (CO2) in combustion streams used to generate electricity. The utilization of eggshell waste in CO2 capture via cyclic carbonation-calcination reactions (CCR) was investigated in this work. Using thermogravimetric analysis, the CO2 capture capacity for multiple acetic acid pretreated eggshell samples was studied. This pretreatement generates a mesoporous structure, allowing the eggshell-derived sorbent to reach higher conversions over more CCR cycles while also removing the eggshell's protein-rich membrane. Six acetic acid treatments were also explored for regeneration of spent sorbents after multiple cycles. The regeneration of spent sorbents with acetic acid provided a 38% improvement in CaO untreated shells after ten cycles. The eggshell membrane contained highly valuable Type X collagen, which can be recovered through the course of shell pretreatment to increase process feasibility. This scheme allows for sustainable generation of CaO sorbents while also transforming a current waste material into a value-added product.