Experimental measurements and modelling of the CO2 solubility in L-lysine co-promoted CESAR-1 (Bio-CESAR) solutions

Carbon capture technologies are vital for mitigating carbon dioxide (CO2) emissions in bioenergy and energy-from-waste power plants. Among them, solvent-based absorption is the most widely used in above industries. Mono-ethanolamine (MEA) is the pre-dominant and an established solvent for absorption based-carbon capture. However, newer solvent blends, like mixtures of MEA and N-methyl diethanolamine (MDEA), and CESAR-1 (a blend of 2-amino-2-methyl-1-propanol and piperazine) are being considered for future plants as they offer 10–15% enhanced performance and ∼20% improved capacity. This study presents the first results of adding L-lysine as a co-promoter for CESAR-1, to improve its CO2 capture efficiency and capacity. The proposed blend, Bio-CESAR (a blend of 2-amino-2-methyl-1-propanol, piperazine, and L-lysine), was experimentally tested for CO2 solubility across a range of pressures (30–500 kPa, CO2 partial pressure range of 3–50 kPa) and temperatures (298.15–343.15 K), and its performance was compared to conventional CESAR-1 and MEA solutions. Results show that Bio-CESAR offers 15% higher CO2 loading and equilibrium CO2 solubility at average compared to CESAR-1, suggesting potential for improved cyclic efficiency in industrial applications. The enhanced CO2 absorption performance of Bio-CESAR is attributed to the incorporation of L-lysine, which modifies CO2–solvent interactions and solution speciation within the CESAR-1 framework. Results from this macroscopic study suggest that the bio-derived amino acid act synergistically with the conventional amine components, leading to improved equilibrium CO2 loading. This study provides a fundamental insight for the use of L-lysine (and not its alkaline salt) in enhancing solvent performance and reducing environmental risks in carbon capture systems.