Senior research scientist Radu Custelcean and colleagues from Oak Ridge National Laboratory came up with a new more efficient direct air capture process. They use the inexpensive peptides and guanidines to capture the CO2 instead of the traditional DAC process using aqueous hydroxide solutions or solid amine-based sorbents.
The new method also requires up to three times lower heating temperatures than the traditional ones. All that has the potential to increase the overall efficiency of the DAC technology and how well it scales up.
The DAC process normally has high energy requirements. When aqueous solvents or solid adsorbents are used for the capture of CO2, their energy requirements are quite high – in the range of 8.4-12.5 and 4-6 GJ/t of captured CO2 respectively. When aqueous solvents are used, up to 90% of the total energy required from the process goes to sorbent regeneration.
Unless the energy demand of the DAC process is not reduced significantly, scalability remains economically unfeasible. Therefore, the widespread implementation of the DAC technology needed to mitigate climate change remains hindered.
The New Direct Air Capture Process Explained
This new process might provide a potential solution. It requires just 3.45 GJ/t of captured CO2. It uses a peptide solution that reacts with the carbon dioxide. Those reactions transform the CO2 into bicarbonate ions. A guanidine compound is then added, which scavenges protons and bicarbonate ions, recovers the amino acids and forms guanidine-carbonate crystals. Mildly heating the crystals restores the guanidine and releases the CO2 for storage or use.
One major advantage of peptides is that, with the dozens of possibilities of combining them, they are a structurally diverse platform for designing new DAC systems with optimized CO2 capacities, absorption rates, and regeneration energies.
Although the regeneration reaction of the peptide solution with the CO2 and the release of the CO2 from the crystals are highly favorable, the precise energy efficiency, the economic and environmental feasibility of the proposed DAC process will need to be determined.
That will include calculating the cost, energy consumption, and carbon footprint of the process. Further techno economic and life cycle assessments evaluating these factors are expected to be reported soon.
Although peptides have received little attention so far as DAC sorbents, their efficiency of capturing CO2 has been determined. Significant advantages of the new direct air capture have been established that outperform traditional approaches in terms of energy requirements and potentially cost.
