Direct Air Capture Committee Members: Jen Wilcox, Chris Jones, Mark Barteau, Dane Boysen, and Peter Kelemen

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1 Direct Air Capture Committee Members: Jen Wilcox, Chris Jones, Mark Barteau, Dane Boysen, and Peter Kelemen

2 Carbon Dioxide Removal Using Negative Emissions Technologies Options and Impact Gasser et al. estimate removals of ~ GtCO 2 /yr in their best-cast scenario and GtCO 2 /yr in their worst-case scenario to prevent 2 C warming by Negative feedback can reduce the scope one-ton reduction of CO 2 in the air requires 2 tco 2 removal never should this be a replacement for mitigation (always easier) We are asking future generations to pay more later than today s generations to pay less now IPCC reports costs will be up to 138% greater if CCS not included in portfolio and up to 64% greater if BECCS is excluded; 44% increase if delayed through NET Option 2100 Potential (GtCO 2 /yr) DACS ~ 4-12 Mineral Carbonation ~ 1 4 References: Gasser et al., Nature Commun., 6, 2015; Tavoni and Socolow, Climatic Change, McNutt et al., NAS Report, 2014.

3 Examples of Direct Air Capture CE-DAC 20m tall x 5m deep x 200m long 1,000,000 tonnes CO 2 /year Containerized GT-DAC 3 x ~ 12m process containers 4,000 tonnes CO 2 /year References: Holmes and Keith, 2012; Eisenberger, personal communication

4 Challenges and Unique Design Aspects of DAC To compensate for the low partial pressure driving force, need strong bases/binding, which lead to increased regeneration energy may require a chemical shift rather than simple pressure or thermal shift in the case of solvent separation Amount of air processed tall tower is not required if 50% capture rate assumed, reducing a volume of gas from 400 ppm down to 200 ppm contrast to a 90% capture from an exhaust stream short tower for DAC also desired to minimize the energy required to overcome the pressure drop For conventional plant (i.e., amine scrubbing on 500-MW power plant), fan or blowers may comprise up to 3-5% of the total energy, but in DAC may dominate depending on the tower height and pressure drop Reference: Mac Dowell, Herzog, Wilcox, et al., Energy Environ. Sci., in review

5 The Difficulty of Direct Air Capture Energy scales with dilution! DAC is always 20 kj/mol CO 2, for > 50% capture and > 80% purity Density changes with purity 95%CO 2 + 5%N 2 = 681 kg/m 3 80%CO %N 2 = 343 kg/m 0.5 kj/mol CO 2 additional compression energy! Reference: Wilcox, Carbon Capture, 2012

6 Economics of DAC How to reconcile the wide range of costs in the literature? < $50/tCO 2 (Lackner) ~ $200/tCO 2 (Keith) $600 - $800/tCO 2 (APS Study; Mazzotti et al.) $1000/tCO 2 (House et al.) Identifying boundary conditions Capture unit only Capture + regeneration Capture + regeneration + sequestration Final purity References: Lackner et al., Proceedings of the First National Conference on Carbon Sequestration, 2001; Heidel et al., Process Design and Costing of an Air-contactor for Air-capture, Information Sheet, Carbon Engineering, 2011; Socolow et al., APS Study, 2011; Mazotti et al., Clim. Change, 2013; House et al., Proc. Nat. Acad. Sci., 2011.

7 Simple Relationship - Sherwood $1000/ton $100/ton ppm the recovery of potentially valuable solutes from dilute solution is dominated by the costs of processing large masses of unwanted materials. - Edwin Lightfoot References: House et al., Proc. Nat. Acad. Sci., 2011; Calculations using IECM for 500-MW plant

8 2 Very Different Pilot-Scale Technologies Air contactor absorbs CO 2 into KOH and makes K 2 CO 3 Chemical swing process Goal is to produce high-purity CO 2 Filter module w/ spacers and active sheets of material Pilot concentrates CO 2 to 0.25% to 1% Lab-scale achieves up to 5% References: Geoff Holmes, Carbon Engineering (personal communication); Klaus Lackner (personal communication)

9 Energy and Material Balances of Generic Processes Solvent Approach w/ KOH References: Geoff Holmes, Carbon Engineering (personal communication)

10 Siting DAC Plants Potential Considerations energy mix, water, sequestration Reference: Psarras et al., WIREs Energy and the Environment, 2017

11 Over-Arching Goals of Workshop Identify technical challenges associated with the commercial-scale approaches underway today and outlining the research agenda to overcome them Identify aspects of a given process that are the most energetic and costly and outlining opportunities that minimize losses in efficiency Hear from the CCS community to understand lessons learned from conventional approaches and the scalability Discussion of the policy framework that could be in place that may help to incentivize pathways to implementing more DAC projects on a commercial scale Discussion of system-based integrated approaches to DAC that include CO 2 storage and the incorporation of renewables To ultimately develop a research agenda and quantify to what extent a program on DACS should be considered by various funding agencies