About This Project

We investigate technoeconomics and aspirational CA targets for CA-enhanced KOH/K2CO2 DAC processes with electrochemical sorbent regeneration. We use i) state-of-the-art modelling with bespoke electrolyser models integrated in process modelling software and ii) true prospective technoeconomic analysis methods to answer robustly how well CA needs to perform to bring this DAC technology to <$300/tCO2, striving for $100/tCO2, by 2050.

Ask the Scientists

What is the context of this research?

The US government target scale & cost for air carbon dioxide removal (CDR) is 1-10 Gt CO2/yr at $100/tCO2 by 2050, recent work shows a more plausible Gt-scale cost range is $100-600/tCO2 net removed (1). Direct air capture (DAC) is easily verifiable and durable, but is currently estimated to cost ~$350-3000/tCO2 net removed (1). The primary cost factors are the CapEx and the energy required to drive large temperature or pH swings to regenerate CO2 from the capture material (1). Liquid DAC’s high cost and energy requirements are driven by a trade-off between the rate of CO2 absorption and the CO2 regeneration energy: CO2 capture absorbents with high absorption rate can reduce cost by reducing the air contactor size, but typically have high CO2 regeneration energy, and vice versa (2)

What is the significance of this project?

Carbonic anhydrase (CA) enzymes catalyze CO2 exchange. CA can enable fast CO2 absorption in capture absorbents with low CO2 regeneration energy, resolving the tradeoff discussed above (3). CA could enable efficient DAC with smaller temperature or pH swings if it can be stabilized in DAC processes, which may include high pH, temperature, or ionic strength.

Protein engineering (PE) and novel CA discovery through systematic screens of natural variants could produce stable CA for DAC. However, no designs for CA-optimized DAC are proposed, so it is unclear what conditions CA must be engineered to tolerate. Design-oriented techno-economic analysis (TEA) could enable CA-enhanced DAC development by identifying optimal process conditions and providing clear targets for PE.

What are the goals of the project?

We investigate technoeconomics and aspirational CA targets for CA-enhanced KOH/K2CO3 DAC processes with electrochemical sorbent generation, answering the following questions:

1. What are the key process drivers of energy performance and spatial footprint for liquid DAC with pH-swing regeneration?

2. Which operating conditions minimize DAC contactor footprint, electrolyser stacks needed, and energy requirements for absorbents with added 'ideal' CA (kov >10E8 1/Ms) and 'reasonable' CA (kov >10E6/7 1/Ms)?

3. How do the costs of this technology change across RQ2's process designs with changing CA cost and lifetime?

4. What are the minimum CA properties needed and corresponding process parameters for use of CA in liquid DAC to render CO2 removal costs below $300/tCO2, striving for $100/tCO2?