Authors: David Sandalow Center on Global Energy Policy, Columbia University Chair, ICEF Innovaton Roadmap Project Julio Friedmann Center on Global Energy Policy, Columbia University Energy Futures Initatve Colin McCormick Walsh School of Foreign Service, Georgetown University Valence Strategic Sean McCoy Department of Chemical and Petroleum Engineering, University of Calgary This roadmap was prepared to facilitate dialogue at the Fifh Innovaton for Cool Earth Forum (Tokyo October 2018), for fnal release at COP-24 (Katowice December 2018). Contents

iv Introduction Chapter 1 1 Carbon Dioxide Removal Technologies Chapter 2 9 Direct Air Capture Technologies

Chapter 3 15 Advantages of Direct Air Capture

Chapter 4 19 Challenges Facing Direct Air Capture

Chapter 5 21 Direct Air Capture Technology Pathways

Chapter 6 31 Policy Considerations

Chapter 7 37 Findings and Recommendations

December 2018 iii been used in submarines since the 1940s and spaceships Introducton since the 1950s. The movie Apollo 13 recounts a dramatc efort to design a CO2 scrubber aboard a Concentratons of carbon dioxide in the damaged spacecraf en route to the Moon. This roadmap explores the potental for direct air atmosphere have reached their highest capture of carbon dioxide to contribute to climate levels in roughly three million years. mitgaton (and provide feedstock for commercial processes). Chapter 1 of the roadmap examines the Those concentratons contnue to climb, year afer year. need for carbon dioxide removal broadly and surveys the The Intergovernmental Panel on Climate Change (IPCC) range of CDR approaches available. Chapter 2 describes warns of extraordinary risks (including from storms, direct air capture technologies. Chapter 3 discusses the foods, droughts, heat waves and sea level rise) unless advantages of direct air capture. Chapter 4 explores the buildup of carbon dioxide in the atmosphere slows challenges facing direct air capture, and Chapter 5 and then reverses in the decades ahead.1 considers research pathways for addressing them. More than 175 natons have now ratfed the Paris Chapter 6 discusses policy optons. Chapter 7 ofers Agreement, which calls for countries to achieve net fndings and recommendatons. zero emissions of greenhouse gases in the second half of this century. However, progress towards that goal is 1 See IPCC, Global Warming of 1.5°C: Summary for Policy slow. Few major economies are now meetng their inital Makers (2018) at p.13, htp://report.ipcc.ch/sr15/pdf/ reducton targets under the Paris Agreement. Strategies sr15_spm_fnal.pdf, IPCC, Fifh Assessment Report for deep decarbonizaton of some sectors of the global Working Group 1 – Informaton from Paleoclimate Records (2013) at p. 394, htps://www.ipcc.ch/site/ economy remain unclear. assets/uploads/2018/02/WG1AR5_Chapter05_FINAL. Against this backdrop, carbon dioxide removal (CDR) pdf; NASA, Carbon Dioxide Hits New High, htps:// has grown in prominence as a component of global climate.nasa.gov/climate_resources/7/graphic-carbon- dioxide-hits-new-high. climate strategies. CDR refers to a range of approaches for drawing carbon dioxide (CO2) from the atmosphere 2 IPCC, Global Warming of 1.5°C: Summary for Policy using biological, engineered or hybrid means. Examples Makers (2018) at p.19, htp://report.ipcc.ch/sr15/pdf/ of CDR include aforestaton, bioenergy with carbon sr15_spm_fnal.pdf. capture and storage (BECCS), and direct air capture of carbon dioxide (DAC). Removal of carbon dioxide from the atmosphere has the potental to play a signifcant role in climate mitgaton, supplementng the many vitally important strategies for reducing and preventng emissions of carbon dioxide in the frst place. Indeed the IPCC’s Global Warming of 1.5°C report (2018) states that 100-1000 gigatons (GT) of carbon dioxide removal will be required this century to prevent global average temperatures from climbing 1.5°C (2.7°F) above pre- industrial levels.2 Carbon dioxide can be captured directly from air using chemicals, refrigeraton or membranes. Some of these techniques date to at least the 1930s, when air

separaton units designed to produce oxygen produced nasa.gov source: CO2 as a byproduct. (This CO2 was ofen sold to the food Figure 1-1. The improvised carbon dioxide scrubber on and beverage industry.) Atmospheric CO2 scrubbers have board the Apollo 13 lunar module.

iv December 2018 remaining amount of the below 2°C carbon budget is Chapter 1 equivalent to roughly 28 years of global CO2 emissions at current rates. The remaining amount in the below 1.5°C carbon budget is equivalent to roughly 10 years of global Carbon Dioxide CO2 emissions at current rates.6 Both these estmates are subject to uncertaintes due Removal Technologies to factors including diferences in radiatve forcing estmates, pathways for emissions of non-CO2 gases A. Need for Carbon Dioxide Removal (e.g., methane, nitrous oxide and aerosols) and other Global average temperatures are increasing due to factors. (See Box 1.) emissions of greenhouse gases, the most important of Although there are uncertaintes with respect to the which is CO2.1 In the Paris Agreement, more than 180 precise values of the carbon budget for any stabilizaton countries agreed to: target,11 there is no uncertainty with respect to three “hold the increase in the global average important conclusions: temperature to well below 2°C above pre-industrial 1. to keep global average temperatures from increasing levels and pursue eforts to limit the temperature 2°C (3.6°F) or 1.5°C (2.7°F) above pre-industrial increase to 1.5°C above pre-industrial levels.” 2 levels , the remaining carbon budgets are small in The IPCC estmates that, in order to have a 67% chance relaton to past human emissions of greenhouse gas, of preventng global average temperatures from 2. with each passing year those budgets grow smaller, increasing 2°C (3.6°F) above pre-industrial levels (the and “below 2°C carbon budget”), emissions of CO2 afer the beginning of 2018 must be kept below 1170 GtCO2 (319 3. the tme remaining before we exhaust those carbon GtC).3 The IPCC also estmates that, in order to have a budgets is very small compared to the tme required 67% chance of preventng global average temperatures to transiton to a zero-emissions society.12 from increasing 1.5°C (2.7°F) above pre-industrial levels The primary motvaton for CDR is the expectaton that (the “below 1.5°C carbon budget"), emissions of CO 2 CO2 emissions will not be reduced rapidly enough or to a afer the beginning of 2018 must be kept below 420 level low enough to keep within the carbon budget. This GtCO (114 GtC).4 2 implies that withdrawing CO2 from the atmosphere will To put this in perspectve, annual CO2 emissions from be necessary in the future.13 Future climate scenarios human actvites are roughly 42 Gt (11 GtC).5 Thus, the that seek to limit temperature increases to 2°C (3.6°F)

BOX 1 The impact of non-CO2 greenhouse gases on the carbon budget Non-CO2 GHGs and aerosols have a strong impact on climate but also tend to be short-lived.

For example, methane (CH4) and nitrous oxide (N2O) have lifetmes in the atmosphere of around 12 years and 121 years, respectvely.7 In contrast, a substantal fracton of CO2 emited today will persist for millennia, contributng to warming over that entre tme8—a factor in determining the carbon budget. If all non-CO2 GHG and aerosol emissions were halted today, their climate impact would diminish within decades, while CO2 emissions would contnue to warm the planet for centuries.9 Small diferences in the future emissions trajectories of non-CO2 GHGs and aerosols can have a strong impact on the carbon budget. Both CO2 and non-CO2 greenhouse gas emissions must be addressed to tackle climate change.10

December 2018 1 (e.g., IPCC RCP2.6) refect this expectaton, as most example, ocean alkalinity modifcaton techniques could require CDR technologies to deliver “net negatve” help ofset ocean acidifcaton resultng from the mixing emissions afer 2050.14 (See Box 2.) of CO2 from the atmosphere into the ocean. Similarly, approaches to increase soil carbon could also increase the Even if emissions were aggressively reduced—far ability of soil to retain water, improve plant growth and more than implied by current natonally determined limit runof during extreme precipitaton events, which contributons (NDCs)—CDR would be required to achieve are expected to increase as a result of climate change. warming limited to 1.5°C (2.7°F).15 Indeed, in its Global Warming of 1.5°C report (2018), the IPCC found that all As this secton highlights, much of the carbon budget pathways to a 1.5°C (2.7°F) stabilizaton target require available for limitng warming to 2°C (3.6°F) has already signifcant CDR—between 100 and 1000 GtCO2 through been exhausted and the remaining space in the budget 2100.16 is shrinking rapidly. Ambitous mitgaton eforts are required to stretch this remaining budget for as long While the primary motvaton for CDR is the expectaton as possible. CDR pathways are not a substtute for that we will be unable to meet the constraints imposed conventonal mitgaton approaches but will be needed by the carbon budget, some CDR approaches could as a supplement to deep emissions reductons.18 also serve to reduce the impacts of CO2 emissions.17 For

Cost Energy Land Water Risk of Verifiability Implement Requirements Use Consumption Reversal Readiness

Reforestation & Enhanced Forest Management

Wetland & Coastal Restoration NATURAL Soil Carbon Restoration

DACS 2 CO

Terrestrial Enhanced Weathering

Ocean Alkalinity TECHNOLOGICAL Modification

Hybrid Bioenergy with CCS (BECCS)

HYBRID Bioenergy with Biochar Sequestration (BEBCS)

LEGEND Generally Acceptable/ Available Exercise Caution Potentially Unacceptable/ Unavailable

Figure 1-2. Summary table of pathways in the CDR portolio, highlightng strengths, weaknesses and indicatve technical potental.

2 December 2018 BOX 2 What does “net-negatve” mean? The term “net-negatve” appears in both the discussion of carbon dioxide removal (CDR) technologies and long- term emissions trajectories. CDR technologies are ofen viewed as simply a mechanism for removing CO2 from the atmosphere. Unfortunately, they will also be responsible for emitng some amount of CO2 themselves. For example, direct air capture (DAC) plants will be built from plastcs, steel and cement, the producton of which emits CO2 and may consume energy that is not from zero-carbon sources. Therefore, the correct way to consider the climate impact of CDR technologies is in terms of “net” CO2 removal, which is the amount of CO2 removed minus any corresponding emissions resultng from removal or as a consequence of removal. This highlights the importance of examining the removal process from a full lifecycle perspectve. If enough CDR is deployed, global emissions could also become “net-negatve.” This means that emissions from all human actvites—such as power generaton, industry, transport and CDR—are smaller than the amount of CO2 removed from the atmosphere. The result would be a decrease in atmospheric concentratons of CO2. For the same “net-negatve” emissions target, the lower the emissions from human actvites, the lower the required CO2 removal rate.

B. Carbon Dioxide Removal Portfolio Examples of natural pathways include reforestaton, Direct air capture (DAC) is one of several CDR improved forest management, use of cover crops pathways.19 (See Figure 1-2.) No single CDR pathway will in farming, changes to animal grazing practces and likely be able to deliver all the carbon dioxide removal restoraton of wetlands, peatlands and coastlines (ofen 22 needed to stay within the below 2°C budget.20 referred to as “blue carbon”). These pathways were the subject of a major study The cumulatve potental of natural pathways to remove by the U.S. Natonal Academies to assess the state of CO2 is large relatve to current annual emissions. current CDR approaches and to develop a research, Moreover, in additon to removing CO2, many natural development and demonstraton (RD&D) agenda for pathways enhance other ecosystem services, such as many key CDR pathways.21 The study concluded that all regulatng water fow or reducing erosion. The potental approaches have merits and challenges. Importantly, of a wide range of natural pathways was recently the study concluded that neither the U.S. nor the world estmated at 14 GtCO2/y in 2030 (afer accountng 23 can achieve the required rate and volume of CDR using for “safeguards”) , of which around 5 GtCO2/y was 24 pathways available today below a $100/tCO2 cost. For estmated to cost less than $100/tCO2 . However, all 2°C pathways, additonal deployment of CDR was these pathways are limited by the availability of land, 25 needed at costs above $100/tCO2 today. The report water and nutrients. Moreover, this type of approach concluded that innovaton, research, development and may have drawbacks such as reductons in crop or investment are needed to reduce cost, increase potental grazing land, biodiversity (e.g., replacing virgin forest volume and rates, and manage the trade-ofs between with managed plantatons) or albedo (i.e., increased land, cost, energy requirements and other important absorpton of solar radiaton and, thus, local heatng). constraints. Many of these pathways are also subject to saturaton (CO2 removal from trees slows over tme) and may be CDR approaches can be grouped into natural, reversible (e.g., forest fres releasing previously removed technological and hybrid pathways. Natural pathways CO2), meaning that their aggregate removal rates are those in which ecosystems are conserved, will decline over tme and could release CO2 under a restored or managed to remove carbon dioxide from changing climate. the atmosphere and increase carbon sequestraton.

December 2018 3 Ocean fertlizaton, where nutrients are spread over rates of millions of tons per year,37 and modeling nutrient-limited regions of the ocean—enhancing algal studies suggest these projects are not outliers.38 In growth and CO2 uptake26—can also be considered a additon to geological storage, conversion of CO2 into natural pathway. However, the efciency of ocean aggregates and durable products could also be a means fertlizaton appears low, and the actvity may have of sequestering CO2, albeit at a much smaller scale.39 substantal negatve impacts on the ocean ecosystem.27 This suggests that DAC with sequestraton (“DACS”) Because of the uncertaintes about its efectveness, could play an important role as a “backstop” technology status in internatonal law and concerns about in an overall climate strategy (see Chapter 3 for further unintended consequences, we do not consider ocean discussion). fertlizaton in this document. Hybrid pathways harness both ecosystems and Technological pathways depend fundamentally on technological systems to remove CO2. This category deployment of engineered technological systems to encompasses bioenergy with carbon capture and storage remove CO2. These pathways include DAC28, indirect (BECCS),40 in which biomass is converted to electricity or ocean capture29, terrestrial-enhanced weathering30 and fuels and the resultng CO2 is captured and geologically ocean alkalinity modifcaton.31 The cumulatve potental stored; and bioenergy with biochar carbon sequestraton of some of these pathways has been individually (BEBCS), where agricultural soils are amended with evaluated and is very large, but their practcal potental is charcoal derived from bioenergy processes.41 The capture poorly understood. For example, accelerated weathering and subsequent sequestraton of CO2 released from using mined, crushed silicate rocks spread on suitable bioenergy and small-scale producton of biochar (for croplands could remove billions of tons of CO2 annually use as a soil amendment) are undertaken today. A wide at costs well below $100/tCO2.32 At very large scales, range of studies suggests that both BECCS and BEBCS alkaline runof from such enhanced weathering would could be deployed at levels sufcient to remove billions partally mitgate ocean acidifcaton.33 In contrast, ocean of tons of CO2 annually.42 In both of these cases, factors alkalinity modifcaton schemes directly increase the limitng large-scale deployment will likely be competton alkalinity of the oceans—mitgatng ocean acidifcaton— for land and water and nutrient demand for biomass while sequestering atmospheric CO2. Some of these producton.43 Biomass is used widely as a fuel today, pathways (e.g., electrochemical weathering) also have supplying approximately 10% of primary energy demand the beneft of generatng hydrogen.34 However, the globally (55 EJ/y) in 2015.44 Creutzig et al.45 report that principal challenge with large-scale (i.e., multple GtCO2 there is a “medium level of agreement” that this could per year) use of enhanced weathering or ocean alkalinity be increased up to 300 EJ/y in a sustainable manner. modifcaton is the need to mine and process enormous Reversibility of carbon removal is a queston that is amounts of virgin rock.35 Additonally, where large-scale frequently raised in the context of DACS, BECCS and enhanced weathering impacts the oceans, it could be BEBCS, as well as in natural pathways, as discussed limited by marine dumping treates (e.g., the London above. While carbon contained in biochar tends to be Conventon and Protocol). relatvely stable in the soil, the factors afectng the The cumulatve removal potental of DAC is constrained permanence of carbon sequestraton, the relatonship by the available capacity for geological (or other) between soil types and productvity benefts of biochar sequestraton, while the rate is limited by power applicaton, and the relatonship between feedstocks and requirements of DAC and the rate at which CO2 can be producton conditons needs to be beter understood.46 sequestered. The global geological storage capacity Conversely, the permanence of geological storage and for CO2 is equivalent to hundreds of years of emissions the associated risks are relatvely well understood.47 (though this large theoretcal capacity must be resolved Research and development, demonstraton projects, on a case-by-case basis through further exploraton and and analogues support the expectaton that CO2 stored characterizaton).36 Sustainable rates of CO2 injecton in well-characterized geological formatons using best into the subsurface are, likewise, controlled by local practces will be retained for geological tme scales with factors. However geological storage projects currently relatvely low (and manageable) risks.48 in operaton have demonstrated sustained injecton

4 December 2018 In summary, while it is not possible to sum up the Intergovernmental Panel on Climate Change, ed. T. F. current estmates of potental for each of these Stocker et al. (Cambridge, U.K.: Cambridge University pathways, it appears that a relatvely low-cost portolio Press, 2013), htp://www.climatechange2013.org/ images/report/WG1AR5_Chapter08_FINAL.pdf. of CDR actvites could be created to remove billions of tons of CO2 per year from the atmosphere. Given the 8 F. Joos et al., “Carbon Dioxide and Climate Impulse large removal potental associated with DAC coupled Response Functons for the Computaton of to geological CO2 storage relatve to the other CDR Greenhouse Gas Metrics: A Mult-Model Analysis,” Atmospheric Chemistry and Physics (March 2013) at pathways, DAC does set an upper limit on the cost p.2793–2825, htps://doi.org/10.5194/acp-13-2793- 49 of climate mitgaton. However, DAC does not ofer 2013. the co-benefts that are associated with some other 9 pathways, ranging from energy producton (e.g., Collins et al., op. cit. BECCS, electrochemical weathering) to enhancement 10 Joeri Rogelj et al., “Disentangling the Efects of CO2 and of ecosystem services (e.g., forest conservaton and Short-Lived Climate Forcer Mitgaton,” Proceedings reforestaton). The ultmate compositon of the CDR of the Natonal Academy of Sciences (October 2014), technology portolio depends on future developments in 201415631, htps://doi.org/10.1073/pnas.1415631111. technology, policy and behavior. 11 Glen P. Peters, “The ‘Best Available Science’ to Inform 1.5 °C Policy Choices,” Nature Climate Change (July 2016) at p.646–49, htps://doi.org/10.1038/ 1 Mathew Collins et al., “Long-Term Climate Change: nclimate3000. Projectons, Commitments and Irreversibility,” Climate Change 2013 - The Physical Science Basis, by IPCC 12 Vaclav Smil, “Examining Energy Transitons: A Dozen (Cambridge, United Kingdom: Cambridge University Insights Based on Performance,” Energy Research & Press, 2013) at p.1029–1136, htps://doi.org/10.1017/ Social Science (December 2016) at p.194–97, htps:// CBO9781107415324.024. doi.org/10.1016/j.erss.2016.08.017. 2 Paris Agreement, Artcle 2.1(a), htps://unfccc.int/sites/ 13 Sabine Fuss et al., “Betng on Negatve Emissions,” default/fles/english_paris_agreement.pdf. Nature Climate Change (October 2014) at p.850–53, htps://doi.org/10.1038/nclimate2392; T. Gasser et 3 IPCC, Global Warming of 1.5°C, Chapter 2: Mitgaton al., “Negatve Emissions Physically Needed to Keep pathways compatble with 1.5°C in the context Global Warming below 2 °C,” Nature Communicatons of sustainable development (2018), Table 2.2 at (August 2015): at p.7958, htps://doi.org/10.1038/ p.108, htps://www.ipcc.ch/site/assets/uploads/ ncomms8958. sites/2/2018/11/SR15_Chapter2_Low_Res.pdf. 14 Sabine Fuss et al., “Negatve Emissions—Part 2: 4 IPPC, op. cit. (Global Warming of 1.5°C, Chapter 2). Costs, Potentals and Side Efects,” Environmental 5 IPCC, Global Warming of 1.5°C: Summary for Policy Research Leters (May 2018): 063002, htps://doi. Makers (2018) at p.14, htp://report.ipcc.ch/sr15/pdf/ org/10.1088/1748-9326/aabf9f. sr15_spm_fnal.pdf. 15 Elmar Kriegler et al., “Pathways Limitng Warming 6 IPCC, Global Warming of 1.5°C: Summary for Policy to 1.5°C: A Tale of Turning around in No Time?,” Makers (2018) at p.14, htp://report.ipcc.ch/sr15/ Philosophical Transactons of the Royal Society A: pdf/sr15_spm_fnal.pdf. See also Richard J. Millar Mathematcal, Physical and Engineering Sciences, et al., “Emission Budgets and Pathways Consistent (May 2018): 20160457, htps://doi.org/10.1098/ with Limitng Warming to 1.5 °C,” Nature Geoscience rsta.2016.0457. (October 2017) at p.741–47, htps://doi.org/10.1038/ 16 IPCC, Global Warming of 1.5°C: Summary for Policy ngeo3031; Katarzyna B. Tokarska and Nathan P. Gillet, Makers (2018) at pp.14, 19, htp://report.ipcc.ch/sr15/ “Cumulatve Carbon Emissions Budgets Consistent with pdf/sr15_spm_fnal.pdf. 1.5 °C Global Warming,” Nature Climate Change (April 2018) at p.296–99, htps://doi.org/10.1038/s41558- 17 Natonal Academies, 2018, Negatve Emissions 018-0118-9. Technologies and Reliable Sequestraton: A Research Agenda: htps://www.nap.edu/catalog/25259/ 7 Gunnar Myhre et al., “Anthropogenic and Natural negatve-emissions-technologies-and-reliable- Radiatve Forcing,” in Climate Change 2013: The sequestraton-a-research-agenda. Physical Science Basis. Contributon of Working Group I to the Fifh Assessment Report of the 18 Natonal Academies 2018, op. cit.

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6 December 2018 38 Simon A. Mathias et al., “Impact of Maximum Allowable Bioenergy (September 2015) at p.916–44, htps://doi. Cost on CO2 Storage Capacity in Saline Formatons,” org/10.1111/gcbb.12205. Environmental Science & Technology (November 44 IEA, “IEA World Energy Balance,” accessed July 28, 2015) at p.13510–18, htps://doi.org/10.1021/acs. 2017, htps://www.iea.org/Sankey/. est.5b02836; Júlio Carneiro et al., “Injecton Rates and Cost Estmates for CO2 Storage in the West 45 “Bioenergy and Climate Change Mitgaton,” op cit.

Mediterranean Region,” Environmental Earth Sciences 46 (March 2015) at p.2951-2962, htps://doi.org/10.1007/ Patrick Brassard, Stéphane Godbout and Vijaya s12665-015-4029-z. Raghavan, “Soil Biochar Amendment as a Climate Change Mitgaton Tool: Key Parameters and 39 David Sandalow et al., “Carbon Dioxide Utlizaton Mechanisms Involved,” Journal of Environmental (CO2U): ICEF Roadmap 2.0” (Innovaton for Cool Earth Management (October 2016) at p.484–97, htps:// Forum, November 2017), htp://www.icef-forum.org/ doi.org/10.1016/j.jenvman.2016.06.063; Lori A. platorm/upload/CO2U_Roadmap_ICEF2017.pdf; Issam Biederman and W. Stanley Harpole, “Biochar and Its Dairanieh et al., “Carbon Dioxide Utlizaton (CO2U)– Efects on Plant Productvity and Nutrient Cycling: A ICEF Roadmap 1.0” (Tokyo, Japan: ICEF Innovaton Meta-Analysis,” GCB Bioenergy 5, no. 2 (2013): 202–14, Roadmap Project, 2016), htp://www.icef-forum.org/ htps://doi.org/10.1111/gcbb.12037. platorm/upload/CO2U_Roadmap_ICEF2016.pdf. 47 Mai Bui et al., “Carbon Capture and Storage (CCS): 40 M. Obersteiner et al., “Managing Climate Risk” The Way Forward,” Energy & Environmental Science (Laxenburg, Austria: Internatonal Insttute for Applied (March 2018) at p.1062-1176, htps://doi.org/10.1039/ Systems Analysis, 2001). C7EE02342A. 41 Dominic Woolf et al., “Sustainable Biochar to Mitgate 48 Rajesh J. Pawar et al., “Recent Advances in Risk Global Climate Change,” Nature Communicatons Assessment and Risk Management of Geologic CO2 (August 2010) at p.56, htps://doi.org/10.1038/ Storage,” Internatonal Journal of Greenhouse Gas ncomms1053. Control (September 2015) at p.292–311, htps://doi. org/10.1016/j.ijggc.2015.06.014; D. G. Jones et al., 42 Fuss et al., op. cit. (“Negatve Emissions—Part 2”); “Developments since 2005 in Understanding Potental Dominic Woolf, Johannes Lehmann and David R. Environmental Impacts of CO Leakage from Geological Lee, “Optmal Bioenergy Power Generaton for 2 Storage,” Internatonal Journal of Greenhouse Gas Climate Change Mitgaton with or without Carbon Control (September 2015) at p.350–77, htps://doi. Sequestraton,” Nature Communicatons (October org/10.1016/j.ijggc.2015.05.032. 2016): 13160. 49 D. W. Keith, M. Ha-Duong and J. K. Stolarof, “Climate 43 Smith et al., “Biophysical and Economic Limits to Strategy with CO2 Capture from the Air,” Climatc Negatve CO2 Emissions,” Nature Climate Change Change (January 2006) at p.17–45, htps://doi. (December 2015) at p.42-50, htps://doi.org/10.1038/ org/10.1007/s10584-005-9026-x. nclimate2870; Felix Creutzig et al., “Bioenergy and Climate Change Mitgaton: An Assessment,” GCB

December 2018 7

■ Cryogenic: Because CO2 has a relatvely high freezing Chapter 2 temperature for a gas, it can be frozen out of the air. Currently, CO2 is recovered from air by freezing, as a byproduct of cryogenic oxygen separaton. Direct Air Capture ■ Membranes: CO2 can be separated from air and seawater using membranes, including ionic exchange Technologies and reverse osmosis membranes. This mimics the way plants and animals separate CO2. Today, CO2 A. What is Direct Air Capture? is separated from seawater during conventonal Direct air capture (DAC) is the physical or chemical desalinaton. separaton and concentraton of CO2 from ambient air. The companies most actvely engaged in DAC mostly Afer capture, this CO2 can be stored underground, used favor chemical approaches, using either liquid solvents for enhanced oil recovery, or used to make products or solid sorbents. Since heat and power are required such as chemicals, fuels and cement. (See Figure 2-1.) to regenerate the key chemical agents, the goal of DAC is distnct from “point-source” carbon capture and many companies and researchers is to improve CO2 sequestraton (CCS) because it removes CO2 from ambient loadings, reduce input energy requirements and costs, air, not fue gas. Today, the community of investgators and improve concentratons of CO2 in the produced gas and practtoners has focused on three diferent classes of mixture. approaches to separate CO2 from the air: Currently, mainstream DAC technologies are based on ■ Chemical: In this class of separatons, CO2 in the reversible chemical sorbents that can be cycled many air reacts with liquid solvents or solid sorbents, tmes to capture and release CO2. The choice of sorbent temporarily binding it. The solvent or sorbent is then material is an extremely important part of DAC system heated or subjected to a vacuum, releasing the CO2 for design since it determines most other aspects of the concentraton. This approach is similar to point-source overall system. Chemical sorbents are of great interest carbon capture systems that remove CO2 from fue gas. in fue-gas carbon capture, and there are signifcant research, development and demonstraton (RD&D)

Low CO2 AIR

AMBIENT AIR Air Contactor ENERGY CO2 Utilization CO2 Geological Storage

Figure 2-1. Direct Air Capture of Carbon Dioxide.

December 2018 9 eforts to develop new variants of these materials. While minimize any loss of material to the passing air before some of this is helpful for DAC design, research on new it is released, which could pose environmental hazards materials specifcally for DAC is extremely limited.1 and increases the amount of sorbent that must be replenished. The primary categories of chemical sorbents that are used in DAC designs are aqueous hydroxides, solid- B. DAC Technologies Today supported amines and solid alkali carbonates (bulk and supported).2 Research on fue-gas capture technology This secton describes the most prominent DAC designs has also included physiosorbent materials, such as to date, including what is known about their sorbent zeolites and metal-organic frameworks (MOFs), which materials, regeneraton strategy, air contactor and other typically bind CO2 much more weakly than chemical aspects. sorbents. However, the limited amount of research on Carbon Engineering. Founded in 2009 with the goal using these for DAC has produced discouraging results of large-scale DAC deployment, Carbon Engineering is since they appear to perform poorly at the very low CO2 the only solvent-based cycle currently in the market. concentratons of ambient air and are also inhibited by Although the Carbon Engineering design is suited for the presence of atmospheric moisture.3 No current DAC large-scale DACS systems, the company is currently designs use primarily physiosorbent materials. focused on combining DAC-derived CO2 with fuel For economic and technical reasons, sorbent materials synthesis (air-to-fuels). Based in Squamish, Britsh must be re-used many tmes, through many cycles Columbia, the company has an operatng facility that of capturing and releasing CO2. This process tends to produces both synthetc gasoline and diesel and partners degrade the material, reducing its ability to capture CO2 with GreyRock for fuel synthesis (a modifed Fischer- and making it necessary to replenish it over tme. An Tropsch process). important design goal in DAC systems is to minimize this Much of the system is described in a recent technical exhauston of material. paper.5 This is the most detailed descripton of a full The term used to describe the stage of releasing DAC system available in the public literature and is captured CO2 from the sorbent material is regeneraton. supported by data from Carbon Engineering’s operatng The most common way to do this is by heatng the pilot. The paper reports the levelized cost of the sorbent material, whether solid or liquid. Where heat is design will be between $94 and $232/tCO2 captured primarily used to regenerate a solid sorbent the process for a mature facility, depending on assumptons about is known as temperature-swing adsorpton (TSA). Some fnancing, utlizing captured CO2 to make liquid fuel, and sorbents can be regenerated by changing the amount of component technology costs. ambient moisture/humidity, and systems that primarily use this efect are known as moisture-swing adsorpton (MSA). A third way to regenerate sorbents is through changing the ambient pressure of the air, which is referred to as pressure-swing adsorpton (PSA).4 These methods can be used in combinaton, depending on the propertes of the sorbent material. A crucial component of DAC designs is how the sorbents are brought into contact with ambient air. This is done using an air contactor, designed to handle both large volumes of air throughput and either the fow of a liquid sorbent or the structural support of a solid sorbent. The structural materials, geometric design, pressure drop and other features of the air contactor are important challenges for DAC designs and dominate capital costs. A further important design consideraton is to Figure 2-2. Direct Air Capture system—Carbon Engineering.

10 December 2018 The sorbent is an aqueous soluton of potassium hydroxide (KOH), which interacts with solid pellets in a slurry reactor that includes a separate aqueous soluton of calcium hydroxide [Ca(OH)2]. A fnal stage recuperates the CO2 in a separate high-temperature calcinaton regeneraton process. The air contactor uses a plastc (low-cost) packing material that is designed to allow the sorbent soluton to fow downwards under gravity while air is blown across it at right angles (cross-fow confguraton), which is uncommon. What’s distnctve about this company: Carbon Engineering is currently the only company pursuing a liquid-solvent-based approach to DAC. This enables a contnuous process which can operate Figure 2-3. Direct Air Capture system—Climeworks. at steady state (in contrast to solid-sorbent-based systems, which are inherently a batch process). Most components of the design are commercially The sorbent is amine supported on solid porous granules available, meaning that their cost and performance arranged in a proprietary flter. The regeneraton is are relatvely well understood. The proprietary air based on a combined temperature- and pressure-swing contactor is made from low-cost, earth-abundant process. The air contactor consists of a set of fans that materials, helping reduce capital costs. move air horizontally across the sorbent flters. The system requires 1,800-2,500 kWh of thermal energy (at The design currently uses a combinaton of renewable 100°C) and 350-450 kWh of electrical energy per ton of electricity and natural gas (burnt in an oxyfred calciner) CO2 (a rato of four to seven tmes more thermal energy to provide heat. In this confguraton, the requirement than electrical energy).11 The thermal energy is currently for heat energy is four tmes greater than for electrical provided by free waste heat from a local incinerator and energy, on a raw energy content basis. The system geothermal energy in the Swiss and Icelandic projects, can operate in an alternatve confguraton in which respectvely. natural gas also provides power, and the CO2 in the fue gas from the turbine is captured by the system and What’s distnctve about this company: Climeworks included in the levelized cost of capture (between 30% was the frst company to deliver CO2 from DAC as and 48% of the CO2 delivered by the overall system a commercial product and the frst to ofer CO2 comes from combustng natural gas, depending on the removal services as a commercial product. While confguraton). The company is working to develop a the inital design included sub-optmal components, purely electrical process in which high-temperature there are straightorward paths to improving these electrical heatng provides thermal energy for the (e.g., replacing shell-and-tube heat exchangers with calcinaton step. higher performing units). They have an intrinsically modular design and an actve factory foor and Climeworks. This company has three pilot plants producton facility. currently in operaton (one in Switzerland, one in Iceland and one in Italy). The frst plant captures approximately The Climeworks Switzerland plant is currently the only 900 tCO2/y and sells the CO2 to a nearby greenhouse.6,7 DAC facility in the world operatng at near-ktCO2/y scale. The second plant is associated with the CarbFix project,8 The free waste heat and the revenue from CO2 sales capturing approximately 50 tCO2/y and sequestering it.9 to the nearby greenhouse suggest that it has favorable The third plant supplies approximately 150 tCO2/y for economics. However, it is difcult to extrapolate this to producton of renewable methane in the framework of a larger installed base of DAC facilites because niche the EU-funded STORE&GO project.10 No cost estmates opportunites for free waste heat and nearby CO2 ofake are publicly available. such as this are limited.

December 2018 11 Climeworks is focused on food-and-beverage and Once commissioned, the facility in Huntsville will be the carbon-removal services at present and is partnering largest DAC plant in the world. The energy source used with the Gebrüder Meier greenhouse in Switzerland will take advantage of the availability of low-temperature and the CarbFix project in Iceland. In additon, they have heat at the specifc site where it will be installed. several partnerships developing synthetc fuels, notably Center for Negative Emissions (Arizona State with Audi and Sunfre (an electrocatalytc fuel synthesis University). This research group is developing a DAC company based in Germany). process based on an anionic exchange resin, which is Global Thermostat. This company has a demonstraton regenerated using moisture swing.16 The group is not plant operatng in California and is completng a currently afliated with a for-proft company developing pilot plant in Huntsville, Alabama that will capture the technology for commercial distributon. The approximately 4,000 tCO2/y.12 The plant will produce CO2 estmated costs of the current design are unclear, but for a global food and beverage company. The company Center leader Klaus Lackner has previously stated they claims that the cost of capture at scale (1 million tCO2/y) are $200/tCO2 for inital prototypes, and would fall to would be $50/tCO2, although it has not made details of $30/tCO2 for Nth-plant through learning-by-doing.17 The its cost estmates public.13 Center has not made engineering details public. The sorbent is amine supported on a porous ceramic The energy requirement is low, at 50 kJ/mol CO2, or “monolith” structure that is normally used for 1.1 GJ/tCO2.18 No estmate is available for the amount automobile catalytc converters. The regeneraton is of electrical energy required. However, this system based on temperature-vacuum swing, using steam at produces CO2 at low concentraton (5%) and does not 85-100°C to strip CO2 from the amine.14 The energy compress it. It also consumes water—approximately requirement is 4.4 GJ of thermal energy and 160 kWh of 5-15 tons/tCO2.19 If a water supply can be secured (at electrical energy per ton of CO2 (a rato of approximately low cost and energy consumpton), then this type of eight tmes more thermal energy than electrical system is partcularly suited to arid environments where energy).15 the necessary evaporaton to drive the moisture-swing process is favored. What’s distnctve about this company: Global Thermostat’s use of mass-produced honeycomb Additional systems under development. Several monoliths for the air contactor enables cheap additonal systems are being developed that are less manufacturing and provides a high surface area per mature than the ones discussed previously. These pressure drop. This reduces the energy requirement include the following: for moving air through the contactor. The company ■ The VTT Technical Research Centre of Finland has has a large set of U.S. and internatonal patents and demonstrated a direct air capture system based a technology with an intrinsically modular design. on an amine-functonalized polymer resin sorbent. The regeneraton is based on both temperature and pressure swing, with a day/night capture cycle. This is not a commercial project but is contnuously operatng at 1-2 kg/day. The mean specifc energy requirement for CO2 capture is 89 GJ/tCO2.20,21 ■ Oak Ridge Natonal Laboratory has demonstrated a proof-of-concept direct air capture system based on an aqueous amino acid soluton. The CO2-loaded amino acids are reacted with a guanidine compound, which leads to the precipitaton of a CO2-containing salt. CO2 is released from the salt with low-grade heat (80- 160°C), making this a liquid-sorbent system with much lower temperature requirements than hydroxide- based systems.22 Figure 2-4. Direct Air Capture system—Global Thermostat.

12 December 2018 ■ The U.S. Naval Research Lab has developed an 6 “World-frst Climeworks plant: Capturing CO2 from air electrolysis/ion-exchange system for extractng to boost growing vegetables”, Climeworks press release both CO2 and hydrogen from seawater. Based on an (May 2017): htp://www.climeworks.com/wp-content/ uploads/2017/05/02_PR-Climeworks-DAC-Plant-Case- electrolytc caton exchange module, a prototype Study.pdf . device has been tested on seawater in Key West, Florida. The current demonstraton device is capable 7 C. Marshall, “In Switzerland, a giant new machine is of making one gallon of jet fuel from the CO2 per day, sucking carbon directly from the air,” Science (June 2017): htps://www.sciencemag.org/news/2017/06/ with a CO removal rate of 5 tons per year.23 2 switzerland-giant-new-machine-sucking-carbon- ■ X (formerly known as Google X) and PARC have directly-air. developed an electrolytc process for extractng CO 2 8 T. Nguyen, “Climeworks joins project to trap CO ”, 24 2 from seawater. Known as Project Foghorn, the system C&EN (October 2017) at p.15, htps://pubs.acs.org/doi/ was focused on utlizing extracted CO2 to make liquid full/10.1021/cen-09541-notw12. fuels. The project was ended in 2016 afer concluding 9 J. Tollefson, “Sucking carbon dioxide from air is cheaper that the process was not economically viable.25 than scientsts thought,” Nature (June 2018): htps:// ■ Skytree is a spin-out of the European Space Agency www.nature.com/artcles/d41586-018-05357-w. (ESA). Their air capture technology was originally 10 Climeworks website, accessed November 18, 2018: developed to make longer space missions possible htp://www.climeworks.com/case-studies/store-and- by extractng the CO2 exhaled by astronauts on board go/.

spacecraf. They are focused on indoor air cleanup but 11 26,27 Y. Ishimoto et al, “Putng Costs of Direct Air Capture produce a high-CO2 concentraton product. in Context,” FCEA Working Paper (June 2017): ■ Infnitree ofers a DAC product based on MSA htps://papers.ssrn.com/sol3/papers.cfm?abstract_ technology (derived from technology developed at id=2982422. the Center for Negatve Emissions at Arizona State 12 Presentaton by Dr. Graciela Chichilniski, CEO, Global University) and is focused on the greenhouse market. Thermostat, August 7, 2018: htps://www.usea. They do not appear to have any currently operatonal org/event/global-thermostats-fexible-co2-capture- installatons. technology. 13 Ishimoto, op. cit. 1 D. Sanchez et al., “Federal research, development, and 14 demonstraton priorites for carbon dioxide removal W. Li et al., “Steam-Stripping for Regeneraton in the United States,” Environmental Research Leters of Supported Amine-Based CO2 Adsorbents,” (January 2018), htps://doi.org/10.1088/1748-9326/ ChemSusChem (June 2010) at p.899-903, htps://doi. aaa08f org/10.1002/cssc.201000131. 15 Ishimoto, op. cit. 2 E. Sanz-Pérez et al., “Direct Capture of CO2 from Ambient Air,” Chemical Reviews (August 2016) 16 T. Wang et al., “Moisture-swing sorpton for carbon- at p.11840-76, htps://doi.org/10.1021/acs. dioxide capture from ambient air: a thermodynamic chemrev.6b00173 analysis,” Physical Chemistry Chemical Physics (January 2013) at p.504-14, htps://doi.org/10.1039/c2cp43124f 3 A. Kumar et al., “Direct Air Capture of CO2 by Physisorbent Materials,” Angewandte Chemie 17 K. Lackner, “Capture of carbon dioxide from ambient Internatonal Editon in English (October 2015) at air,” European Physical Journal (September 2009) at p.14372-7, htps://doi.org/10.1002/anie.201506952 p.93-106, htps://doi.org/10.1140/epjst/e2009-01150-3. 4 L. Ribaldi et al., “Overview on Pressure Swing 18 Ishimoto, op. cit. Adsorpton (PSA) as CO Capture Technology: State- 2 19 of-the-Art, Limits and Potentals,” Energy Procedia Wang, op. cit. (July 2017) at p.2390-400, htps://doi.org/10.1016/j. 20 C. Bajamundi et al., “Direct air capture of CO2: egypro.2017.03.1385 Opportunites and Challenges,” Presentaton (February 5 D. Keith et al., “A Process for Capturing CO2 from the 2017): htp://www.neocarbonenergy.f/wp-content/ Atmosphere,” Joule (June 2018) at p.1573-94, htps:// uploads/2015/03/Bajamundi.pdf. doi.org/10.1016/j.joule.2018.05.006

December 2018 13 21 P. Simell etl al., ‘Fuels and Chemicals from the Sun 24 C.-F. De Lannoy et al., “Indirect ocean capture of and Air,” Presentaton (November 2017): htps:// atmospheric CO2: Part I. Prototype of a negatve ertc.wraconferences.com/wp-content/uploads/ emissions technology,” Internatonal Journal of sites/59/2017/11/Pekka-Simell-VTT-Technical-Research- Greenhouse Gas Control (March 2018) at p.243-53, Centre-of-Finland.pdf. htps://doi.org/10.1016/j.ijggc.2017.10.007. 22 F. Brethomé et al., “Direct air capture of CO2 via 25 Eisaman et al., “Indirect ocean capture of atmospheric aqueous-phase absorpton and crystalline-phase CO2: Part II. Understanding the cost of negatve release using concentrated solar power,” Nature Energy emissions,” Internatonal Journal of Greenhouse (May 2018) at p.553-9, htps://doi.org/10.1038/ Gas Control (March 2018) at p.254-61, htps://doi. s41560-018-0150-z. org/10.1016/j.ijggc.2018.02.020. 23 H. Willauer et al., “Extracton of Carbon Dioxide and 26 Skytree website, accessed November 13, 2018: htps:// Hydrogen from Seawater by an Electrolytc Caton www.skytree.eu/about/. Exchange Module (E-CEM) Part V: E-CEM Efuent 27 “Skytree wins environment category at the Hello Discharge Compositon as a Functon of Electrode Tomorrow Challenge,” Amsterdam Science Park Water Compositon,” NRL/MR/6360—17-9743, Naval (November 2017): htps://www.amsterdamsciencepark. Research Laboratory (August 2017): htp://www.dtc. nl/news/skytree-wins-environment-category-at-the- mil/dtc/tr/fulltext/u2/1038769.pdf. hello-tomorrow-challenge/.

14 December 2018 over tme (even if the carbon that has been removed Chapter 3 remains permanently sequestered). ■ DAC can be sited in a very large number of locatons. The facilites could be sited near high energy resources Advantages of Direct and geologic storage potental (e.g., the Middle East, U.S. Midwest or ofshore) and need not be close to Air Capture populaton centers or sources of emissions. Moreover, the small footprint of DAC facilites themselves and Because direct air capture (DAC) starts with CO2 capture similarites to existng industrial processes mean from the air in any locaton, it can play two fundamental that they could ofen be constructed and operated roles that other carbon dioxide removal technologies at industrial facilites under existng local land-use cannot. It serves as a backstop technology for managing regulatons. climate change and provides CO2 as a feedstock for CO2 ■ utlizaton (CO2U) applicatons. Relatve to other CDR DAC has several technological advantages over fue- approaches, DAC has notable strengths and weaknesses. gas capture. First, DAC does not require the ability to The strengths include: operate in the presence of high levels of contaminants (partcularly SO2, NOx and mercury), which are present ■ The cumulatve removal potental of DAC is very large in some fue gas and can degrade sorbent materials. 1 in relaton to other CDR pathways. These removals Second, while fue gas capture systems are usually can be largely permanent (where CO2 is geologically designed for nearly complete capture of CO2 (because stored or mineralized). the gas only passes once through the system before ■ The land area requirements for DAC are very small being released to the atmosphere), DAC systems need relatve to those for other pathways (unless the energy not necessarily achieve near-complete CO2 removal in for DAC comes from land-intensive energy sources, a single pass of gas through the system. In fact, some such as solar). For example, 12 GtCO2 per year of CDR DAC systems are intentonally designed to capture through BECCS would require between 380 and 700 only a small fracton of CO2 with each pass of ambient million hectares of land for cultvaton of dedicated energy crops2—an area equivalent to at least half the land area of Australia. Moreover, unlike the producton of bioenergy crops for BECCS (or biochar), DAC can be sited on unproductve lands. ■ Water requirements for DAC are far lower than pathways that harness bioenergy crops for carbon removal. For example, BECCS requires around 600 m3 of water for each metric ton of CO2 removed—largely due to biomass cultvaton—while evaporatve losses from DAC are likely less than 25 m3/tCO2. Some DAC approaches produce fresh water as a by-product of operaton, as will be discussed later. ■ DAC has no direct impacts on nutrient cycling and requires no applicaton of additonal nutrients (such as nitrogen or phosphorous fertlizers) in contrast to biomass crop-based pathways,3 ocean fertlizaton and enhanced weathering. ■ Large annual rates of CO2 removal by DAC could be sustained for centuries at the global level, as the geological reservoirs that serve as the sinks for Figure 3-1. DAC facilites can be sited on unproductve 4 captured CO2 are very large. This contrasts with lands, avoiding competton with food and energy crop many natural pathways, whose removal rates decline producton.

December 2018 15 all global emissions all global emissions A 100% mitigation B 100% mitigation

DACS COSTS TODAY DACS COSTS TODAY MAX TOTAL COSTS FUTURE DACS COSTS BY USING DAC MAX

($) ($) TOTAL COSTS BY USING + cost Total mitigation costs + cost Total mitigation costs DAC – cost – cost tons of mitigation required tons of mitigation required Figure 3-2. Conceptual cost curves for total climate mitgaton with DAC as a backstop technology opton.

air through the system (known as “skimming”). save money or avoid costs. The costs grow as more of This reduces the energy requirement and may be the system is decarbonized. When that curve intersects partcularly appropriate for some CO2 utlizaton the present costs of DAC, it is then possible to fully applicatons that require low-purity CO2. decarbonize at that price. ■ Measuring the CO2 benefts from DAC is relatvely The green “wedge” represents costs avoided by choosing simple, especially compared to many of the DAC above a diferent, more expensive opton (e.g., de- natural pathways for CO2 removal. The mass of carbonizing aviaton). The current estmate of the size of CO2 removed from the atmosphere by DAC can be that wedge, based on the integrated assessment models directly measured, as can any emissions or energy of the IPCC, is in the tens of trillions of dollars to achieve consumpton, at the facility level. Where the removed 2°C (3.6°F) stabilizaton by 2100.7 The DACS price point CO2 is geologically stored, accountng for net removals also sets the maximum cost for CO2 climate stabilizaton, is also relatvely simple, provided adequate monitoring with the rate at which stabilizaton can be achieved set 5 is in place to assess any leakage. This stands in by the amount invested in DACS beyond mitgaton of contrast to natural pathways where avoiding reversals total global emissions. Similarly, every increment of cost may require permanent changes to paterns of land reducton associated with innovaton and deployment use and sustained efort to manage carbon stocks of DACS drops the total costs for climate mitgaton and (e.g., forest management). the total costs for climate restoraton (Figure 3-2b). ■ No internatonal agreements are needed to scale up This is a strong case for investment in DAC innovaton DAC. (Such agreements could be essental for large- and deployment today, creatng optonality for climate scale implementaton of ocean-based CDR strategies.) management. These facts create an important setng for DAC—solving DAC can also provide CO2 as a feedstock for car- climate change should never be more expensive than bon-to-products enterprises.8 Since the cost of capture DAC plus sequestraton costs (DACS).6 Figure 3-2a from many industrial CO2 sources (e.g., ethanol, shows that the total cost for 100% decarbonizaton of ammonia and hydrogen producton) is lower than the economy is the area under the climate mitgaton for DAC,9 there is an obvious tradeof: the high price cost curve. The mitgaton curve begins with negatve of DAC-sourced CO2 competes with the beneft it costs (revenues) because many efciency measures provides of a reliable, contnuous source that can be

16 December 2018 delivered anywhere (i.e., independent of pipelines and 1 Natonal Academies, 2018, Negatve Emissions trucks). While CO2 supplied from a statonary (point) Technologies and Reliable Sequestraton: A Research source is almost certain to have a lower inital cost, the Agenda, htps://www.nap.edu/catalog/25259/ transportaton infrastructure to deliver it may be absent negatve-emissions-technologies-and-reliable- or expensive (for example, using trucking). DAC could sequestraton-a-research-agenda supply any locaton anywhere, albeit at higher inital cost 2 Pete Smith et al., “Biophysical and Economic Limits per ton of CO2. to Negatve CO2 Emissions,” Nature Climate Change (January 2016) at p.42–50, htps://doi.org/10.1038/ Use of CO2 drawn from the air also ofers the potental nclimate2870. for truly carbon-neutral or carbon-negatve products, 3 while CO2 captured from fossil fuel sources can—at Smith et al., op. cit. best—reduce emissions. It is also possible that CO2 4 Natonal Academies 2018, op. cit. drawn from the air will be favored by customers who 5 Tim Dixon, Sean T. McCoy and Ian Havercrof, “Legal wish to avoid direct use of fossil CO . As carbon dioxide 2 and Regulatory Developments on CCS,” Internatonal utlizaton (CO2U) technology improves and demand Journal of Greenhouse Gas Control, Special Issue grows for CO2-based products, the market may place commemoratng the 10th year anniversary of the additonal value on products with a negatve CO2 publicaton of the Intergovernmental Panel on emission footprint. In that context, DAC might provide an Climate Change Special Report on CO2 Capture and additonal beneft by meetng customer demand for CO2 Storage (September 2015) at p.431–48, htps://doi. sourced from the air. org/10.1016/j.ijggc.2015.05.024. 6 David Keith et al., “Climate Strategy with CO Capture Some DAC pathways remove substantal amounts of 2 from the Air,” Climatc Change (December 2005) at water from the air, which is produced as fresh-water p.17-45, htps://doi.org/10.1007/s10584-005-9026-x vacuum distllate when CO2 is recovered. This is partc- 7 ularly true for current sorbent systems, which capture Kruger et al., in review between one and two tons of water for every ton of 8 D. Sandalow et al., “Carbon Dioxide Utlizaton (CO2U): CO2 removed. While this has an impact on system-wide ICEF Roadmap 2.0,” Innovaton for a Cool Earth Forum cost and performance (see Chapter 5), in water-scarce (December 2017), htps://e-reports-ext.llnl.gov/ regions this may prove to be a very atractve co-beneft pdf/892916.pdf; I. Dairanieh et al., “Carbon Dioxide of DAC. Utlizaton (CO2U): ICEF Roadmap 1.0,” Innovaton for a Cool Earth Forum (November 2016), htps://www.icef- Currently there are few if any viable approaches for deep forum.org/platorm/artcle_detail.php?artcle__id=109 decarbonizaton of some parts of the transportaton and 9 Leeson et al. 2017, A techno-economic analysis and agricultural sectors (e.g., airplanes and N O emissions 2 systematc review of carbon capture and storage from fertlizer). Low-cost viable pathways may emerge, (CCS) applied to the iron and steel, cement, oil but that is uncertain.10 DAC provides a certain and secure refning, and pulp and paper industries, as well as pathway for deep decarbonizaton of these parts of the other high purity sources, Intl. Jo. GHG Control, v. economy. This underscores the potental role of DAC as 61, pp 71-84, htps://reader.elsevier.com/reader/ a “backstop” technology opton—it is not a license to sd/pii/ htps://reader.elsevier.com/reader/sd/pii/ contnue emissions but rather a strategy to deal with S175058361730289X?token=FC6C7C2C868A2F698E07 DA69CD8CE4F3FA94B88CF267F57E93087DB79B6909 difcult or expensive emissions proactvely and overtly. E67AB8E19F75B3BD532750AD1C40C6815C 10 Royal Society, “Greenhouse Gas Removal” (2018): htps://royalsociety.org/topics-policy/projects/ greenhouse-gas-removal/

December 2018 17

system where it provides CO2 as a feedstock for CO2 Chapter 4 utlizaton.9 ■ DAC is a relatvely large consumer of energy per ton of CO2 removed. Thus, large-scale deployment of Challenges Facing DAC requires an external energy source, such as fossil fuels (only when their use is integrated with DAC and Direct Air Capture their emissions captured and used or stored), nuclear energy or renewable resources (e.g., solar, wind, DAC is currently expensive. Today, DAC costs range from renewable heat, etc.). There is an opportunity cost $300-600/tCO2, with estmates for future Nth-of-a-kind associated with dedicatng carbon-free energy to use costs in the range of $60-250/tCO2.1 DAC is generally for DAC rather than to displacing use of fossil-energy considered to be among the more expensive CDR (without CCS). Conversely, DAC could be coupled with pathways.2 Since these costs are well above today’s bioenergy CCS systems to remove CO2 both directly carbon market prices, DAC will likely need policies for and indirectly. market entry and deployment (see below, Chapter 6). The potental of DAC to contribute to limitng CO DAC’s high costs refect the fact that CO2 is much 2 more dilute in the atmosphere than fue gas. The concentratons in the atmosphere depends on several factors, the most important of which are the carbon concentraton of CO2 in the atmosphere is roughly 0.04%, compared to 5% in natural gas-fred fue intensity of the energy source and the fate of the gas and 12% in coal-fred fue gas. As a result, the removed CO2. An ideal DAC system, optmized for climate impact, would use near zero-carbon energy theoretcal minimum energy needed to separate CO2 from other gases is approximately three tmes larger and sequester removed CO2 in a saline aquifer. In this for ambient air than coal-fred fue gas.3 This minimum case the net removal would be nearly the same as the energy calculaton and others based on real-world gross removal (with minor adjustments for emissions performance4 have suggested to some that DAC could associated with constructng the system). never be a practcal mitgaton technology, partcularly in By contrast, a DAC system that maximizes economic comparison to fue-gas capture. value could be substantally diferent. If it used low-cost These challenges and possible strategies for addressing natural gas (with capture and storage) as the energy them were recognized in the early literature on DAC.5,6 An important study conducted by the American Physical Society7 atempted to parameterize DAC systems using extant technology and energy costs. More recent studies have explored strategies for cost reducton in greater detail.8 Other notable drawbacks for DAC (relatve to other CDR pathways) include: ■ Most CDR pathways ofer benefts besides CO2 removal. Many natural pathways could help achieve additonal global sustainability goals, such as improving biodiversity, reducing runof, improving agricultural practces and ofering a means to adapt to climate change. Other technological and hybrid pathways, such as enhanced weathering, BECCS and BEBCS, generate valuable products, such as electricity, hydrogen and fuels. Coupled with geological storage in saline aquifers, DAC provides no co-benefts (other Figure 3-1. DAC requires more energy per ton than fue-gas than some degree of water producton as discussed capture, because CO2 is more dilute in the atmosphere above), although it could be incorporated into a than in fue gas.

December 2018 19 source and produced liquid transportaton fuel with 1 David W. Keith et al., “A Process for Capturing CO2 from the removed CO2 as feedstock, the net removal could the Atmosphere,” Joule (August 2018) at p.1573–94, be extremely small or even increase absolute CO2 htps://doi.org/10.1016/j.joule.2018.05.006; Robert emissions. Socolow et al., “Direct Air Capture of CO2 with Chemicals,” American Physical Society (June 2011), Given that various policies (e.g., the California Low htps://www.aps.org/policy/reports/assessments/ Carbon Fuel Standard) and consumer preferences may index.cfm; Natonal Research Council, Climate create value for CO2 as a feedstock, the later case may Interventon. be important in the near-term as a driver for innovaton 2 Sabine Fuss et al., “Negatve Emissions—Part 2: and technology scale-up. However, the climate need for Costs, Potentals and Side Efects,” Environmental DAC is ultmately predicated on the permanent removal Research Leters (May 2018): 063002, htps://doi. of CO2 from the atmosphere, implying that it must be org/10.1088/1748-9326/aabf9f. geologically sequestered or mineralized. 3 Socolow et al., op. cit. A related queston concerns the energy requirements 4 Kurt Zenz House et al., “Electrochemical Acceleraton for DAC. To serve a useful climate functon, DAC must of Chemical Weathering as an Energetcally Feasible operate with sources of heat and power that are Approach to Mitgatng Anthropogenic Climate efectvely zero-carbon. While this may be most easily Change,” Environmental Science & Technology accomplished using renewable energy, there could be (December 2007) at p.8464–70, htps://doi. alternatve approaches using fossil energy under certain org/10.1021/es0701816. circumstances (see discussion in Chapter 5). The costs, 5 K. S. Lackner et al., “Carbon Dioxide Extracton footprint and operatng requirements vary substantally from Air: Is It an Opton?,” 1999, htp://www.ost. based on diferent assumptons about the energy gov/energycitatons/servlets/purl/770509-cJeS4J/ source. Since DAC is not well represented in today’s webviewable/. general equilibrium models, there is litle scholarly 6 K.S. Lackner et al., op. cit. economic analysis to inform such questons. 7 Socolow, op. cit. Separately, some scholars and environmentalists are 8 Keith et al., op. cit.; Socolow et al., op. cit.; Natonal concerned that the availability of DAC and other CDR Research Council, op. cit. approaches may disincentvize or displace mitgaton— 9 D. Sandalow et al., “Carbon Dioxide Utlizaton (CO U): sometmes referred to as “moral hazard.”10 Some have 2 ICEF Roadmap 2.0,” Innovaton for a Cool Earth Forum argued that the availability of CDR might lead to rebound (December 2017), htps://e-reports-ext.llnl.gov/ phenomena, reducing incentves to cut CO2 emissions.11 pdf/892916.pdf. Potental technological pathways for reducing DAC costs 10 Jan C. Minx et al., “Negatve Emissions—Part 1: and addressing other challenges in scaling up DAC are Research Landscape and Synthesis,” Environmental discussed in Chapter 5. Research Leters (May 2018): 063001, htps://doi. org/10.1088/1748-9326/aabf9b. 11 Morrow DR. 2014 Ethical aspects of the mitgaton obstructon argument against climate engineering research. Phil. Trans. R. Soc. A 372: 20140062. htp:// dx.doi.org/10.1098/rsta.2014.0062.

20 December 2018 This regeneraton energy is directly related to how tghtly Chapter 5 the sorbent/solvent binds CO2 (which is determined by the enthalpy of the sorbent-CO2 reacton). This suggests that sorbents that bind CO2 only weakly are preferable Direct Air Capture since they require less energy to reverse that reacton and drive of the CO2 during regeneraton.1 However, Technology Pathways no sorbent is perfectly selectve for the CO2 molecule. Other molecules, partcularly water, can also bind to In order to be successful, DAC technology will need the sorbent material, reducing the total amount of to simultaneously achieve low total costs (including CO2 that can be removed per mass of sorbent. In the both capital and operatng costs) and high amounts of case of ambient air, the very low concentraton of CO2 net (lifecycle) CO removal. These two goals interact 2 makes this problem partcularly severe. Unfortunately, in complex ways and involve tradeofs that must be overcoming it generally requires using a sorbent that carefully examined. This chapter will explore the possible binds very tghtly to CO2 and weakly to other molecules. technology pathways to achieve these goals and the Therefore, there is an innate tradeof between reducing constraints they place on DAC design optons. the energy required for regeneratng the sorbent and preferentally absorbing CO over other molecules. A. Reducing Energy Consumption 2 Improved sorbent materials are needed that can As noted in the previous chapter, removing CO2 from the atmosphere takes more energy than removing it from appropriately balance this tension based on a larger a fue gas stream because it is more dilute. Most of the system design. If energy is available at low cost (and with DAC designs that have been proposed to date therefore low CO2 emissions), then sorbent materials with high selectvity for CO would likely be optmal, increasing the consume a signifcant amount of energy per ton of CO2 2 removed. This energy is the primary contributon to amount of CO2 removal per mass of sorbent. If this is not the operatng costs of DAC facilites. Unless this energy the case, then sorbent materials with weaker binding to comes from low-carbon sources, DAC cannot result in CO2 would likely be necessary, at the cost of requiring net-negatve emissions. more sorbent per unit of CO2 removed. Technology pathways to reduce the energy consumpton A further consideraton is the speed of reacton (kinetcs) of DAC are therefore a high priority. It is important to of the sorbent. This impacts the rate at which CO2 can be note that this energy is mostly in the form of heat; as removed from air passing through the system, and thus outlined in Table 1, most DAC designs require four to the size of the air contactor required for a given removal eight tmes more heat energy than electrical energy. capacity. Sorbents with fast kinetcs are therefore This heat is used to regenerate sorbents or solvents desirable. afer they are saturated with CO2. This means the For liquid-solvent-based systems, another consideraton most important goal for reducing energy consumpton is the heat capacity of the liquid. It may be possible to is identfying or developing sorbent and/or solvent further reduce heat energy requirements by using a non- materials that require less energy for regeneraton. aqueous liquid with a lower heat capacity or improving the heat recovery from the liquid during regeneraton.

Table 1: Energy consumpton for major DAC systems as reported. Heat:Power ratos are converted on a raw-energy basis.

Company Thermal energy/ tCO2 Power/ tCO2 Heat: Power rato Reference (GJ) (kWh) Climeworks 9.0 450 5.6 Ishimoto 2017 Carbon Engineering 5.3 366 4.0 Keith 2018 Global Thermostat 4.4 160 7.6 Ishimoto 2017 APS 2011 NaOH case 6.1 194 8.7 APS 2011

December 2018 21 However, any negatve impacts on viscosity, solubility or It is also worth notng that radioisotope thermoelectric other factors would have to be considered in order to generators (RTGs) used by spacecraf operate at identfy the overall energy benefts of alternatve liquids. approximately 1000°C, illustratng the engineering viability of using nuclear fssion to deliver zero-carbon B. Providing Low-Carbon Heat Energy high-quality heat.3 Unfortunately, these systems appear Given the key role that heat plays in DAC systems, it will to be too small-scale to be material for DAC. be important to carefully examine optons for providing Hydrogen combustion: Because hydrogen burns with a low-carbon heat energy. These optons depend on the very high temperature (1900-2600°C), renewably-sourced quality (temperature) that is required. Some DAC designs hydrogen remains a potental source for low-carbon (primarily those using amine sorbents) require relatvely heat that would be of high enough quality for all DAC low-quality heat (90-120°C), while others (primarily applicatons. This hydrogen could be derived from those using hydroxide-based solvents) require higher- conventonal hydrolysis using renewable power (e.g., wind quality heat (500-1000°C). Although many government and solar) or from conversion of renewable feedstocks research, development and demonstraton (RD&D) (e.g., biomass gasifcaton). Advances in electrolyzers and programs around the world include some atenton to biomass gasifers would help reduce costs and improve aspects of renewable heat, these are limited and do not performance of renewable hydrogen, and substantal focus on specifc applicatons to DAC systems. RD&D programs exist today on these topics. Naturally, Nuclear fssion: Conventonal nuclear reactors generate the challenges that apply to hydrogen systems generally high fuxes of zero-carbon heat at medium quality (e.g., pipeline infrastructure, storage systems) would likely (approximately 320°C), which is used to produce steam apply to DAC confguratons that use hydrogen-derived for a Rankine cycle to generate power. This heat is heat. Today, systems to produce renewable hydrogen are mostly too low quality to be useful for DAC systems expensive ($5-10/kg H2), although there are promising using hydroxide-based solvents and is of signifcantly approaches to cost reducton.4 higher quality than the minimum needed for amine- An alternatve to renewable hydrogen is producton of based DAC systems. Ignoring any regulatory or economic fossil hydrogen combined with CCS. Most commonly, hurdles, conventonal reactors therefore may be suitable fossil-derived hydrogen comes from natural gas for supplying heat to sorbent-based DAC systems reformaton, although some countries (notably but appear to be poorly suited for supplying heat for China) produce industrial hydrogen supplies from hydroxide solvent-based DAC systems. coal gasifcaton. These systems commonly produce However, new reactor designs, partcularly those being a highly concentrated stream of byproduct CO2. Four developed for use as small modular reactors (SMRs), sites in the world today capture and store CO2 from may be far more suitable. These reactors could be industrial hydrogen producton – Quest, Port Arthur, Al designed to deliver heat at the appropriate quality for Reyadah and Uthmaniyah.5 Current costs for hydrogen hydroxide-based solvent DAC. They could also be built at producton with CCS provide delivered all-in costs of much smaller scale than conventonal reactors, whose $1.6/kg H2 with 60% reducton of CO2 compared to average thermal capacity is approximately 3.5 GW, conventonal steam reforming systems. Importantly, likely much larger than a single DAC facility could utlize. current estmates to achieve 90% H2 decarbonizaton Adding to their appeal, small modular reactor designs estmate delivery at ~$2.5/kg H2,6,7 substantally less than could potentally be deployed in many geographies, the cost of renewable hydrogen. While this appears to providing local, scale-appropriate, high-capacity heat be a cost-compettve approach to low-carbon hydrogen (and power) for DAC. While this class of reactor has not producton for heat, lifecycle analyses, including the yet been deployed widely, it appears to have cleared upstream emissions associated with natural gas or coal some important regulatory hurdles in the United States producton, must be incorporated to fully understand and may begin entering service soon.2 Research on the viability and limitatons of this approach. system design, costs, integraton needs and lifecycle Fossil fuel combustion with CCS: Fossil combuston would help resolve key questons regarding DAC provides the signifcant majority of process heat in the applicability. world today.8 When combined with CCS, this can provide

22 December 2018 low-carbon heat that could potentally be used for low-cost, high-capacity approach to providing heat. DAC. Notably, one DAC company (Carbon Engineering) Notably, the only full DACS (DAC with sequestraton) uses this approach, combining oxygen-fred natural-gas system in the world (the Climeworks facility in Iceland) combuston with carbon capture as one of its central uses both geothermal power and geothermal heat design optons (delivering CO2 that is a mixture of for operaton. The ability of DAC to be deployed in the combuston product and gas removed from the many geographies could create a market for stranded atmosphere). The costs and viability of these systems geothermal resources (e.g., the Afar triangle in Ethiopia vary substantally from system to system, based on the and La Réunion Island). Additonally, there may be fuel (e.g., coal, gas, pet-coke), combuston method, synergies between geothermal power producton and combuston system design, geography, labor cost, CO2 sequestraton, such as CO2 plume geothermal capture system and other constraints. Full lifecycle (CPG) power producton.11 These optons are largely analyses and applicaton-specifc techno-economic unexplored and unassessed. analysis and designs would help clarify the economic Renewable electricity: Electricity-based heatng and emissions aspects of this method of providing heat technologies are used in a variety of industrial process energy. It may be that this approach has special value heat applicatons. When supplied with renewable in partcular locatons, such as countries with stranded electricity (such as from wind or solar), this is a form of fossil energy assets (e.g., Chad or Indonesia). low-carbon heat and can leverage the rapid growth of Solar thermal energy: Geographic regions with renewable power generaton, as well as scale rapidly. excellent solar energy resources may be able to take The simplest of these (with the lowest capital cost) advantage of concentratng solar energy to create is using renewable electricity for resistve heatng. low-carbon heat. Today, commercial systems focus on Efciencies can reach close to 100% for some materials, concentrated solar power (CSP), which uses the solar and temperatures can exceed 600°C for convecton- heat resource to produce steam for a Rankine cycle to based approaches, although it may be challenging to generate power. These systems are relatvely expensive design systems that heat complex structures, such as air compared to solar PV systems, but they may have an contactors, evenly.12 advantage in direct heat applicatons like DAC. Designs based on parabolic troughs operate at temperatures Heat pumps: Pumps based on the vapor-compression of 400°C and above, while those using power tower cycle can provide process heat up to approximately technology operate in excess of 500°C.9 Even higher 100°C, using heat sources at signifcantly lower temperatures are possible with dish-engine technology. temperatures.13 These systems are commonly used in commercial industrial processes and can achieve high Heat of this high quality may be useful for some solvent- electrical-to-thermal efciencies (up to approximately based DAC systems. For amine-based DAC systems, 300%) by using waste heat or ambient air heat. Notably, lower quality heat is sufcient, and it may be possible high-temperature air-source heat pumps that can to use emerging medium-temperature solar thermal reach 80°C are now commercially available, potentally technologies, such as Schefer refectors and Fresnel providing a source of low-carbon heat for amine-based dishes.10 Conventonal roofop solar thermal systems, DAC systems using only air as the heat source. However, such as those used to provide domestc hot water, are it is important to note that the working fuids for heat generally limited to temperatures that are signifcantly pumps are ofen themselves highly potent greenhouse lower than CSP but stll relevant to amine-based DAC gases (such as hydrofuorocarbons, or HFCs), and any systems. They may also be a source of pre-treatment to leakage of these fuids could signifcantly reduce the reduce the overall heat requirements. overall climate beneft of the system. Alternatves such Geothermal heat: In locatons with favorable geology, as HFO- or ammonia-based working fuids may mitgate geothermal systems can provide a signifcant amount this concern. of low-carbon heat. Most natural geothermal heat Microwave heating systems: Microwave systems resources are geographically restricted and are relatvely can provide industrial process heat for a number of capital-intensive to exploit. However, where geothermal applicatons, including drying grain and lumber in the energy is available, it is likely to prove a very robust,

December 2018 23 agricultural sector and drying powered materials in C. Utilizing Intermittent Renewable pharmaceutcal manufacturing.14 They are generally Electricity most appropriate for non-electrically conductng The increasing penetraton of renewable electricity materials, which is the case for DAC sorbents. Since on many grids has led to curtailment, which is microwave energy can penetrate many materials, it can considered “excess” or “unusable” electricity. Some provide more even heatng throughout a volume than analysts consider this an opportunity for DAC, because applying heat only at a surface; this may be relevant for this otherwise-wasted zero-carbon electricity could DAC designs that use liquid sorbents. Related techniques potentally be used to power DAC plants. This conclusion include radio-frequency heatng and inducton heatng, appears to be strengthened by the fact that DAC facilites both of which are also fully commercialized and used have signifcant fexibility in their locaton and could 15 industrially. thus potentally be sited in areas with large amounts of Waste heat: Heat that is rejected to the environment as curtailed renewable electricity (see below).18,19 a byproduct of industrial actvity is a good candidate for However, curtailed electricity is intermitent and not use by DAC facilites. Generally, waste heat is considered easy to predict on short tmescales (seasonal curtailment low-carbon, since it was not otherwise being utlized. A is generally more predictable).20 This implies that very large amount of waste heat is theoretcally available; DAC facilites using intermitent curtailed renewable for example, there were approximately 25 quads of electricity would either have to ramp up and down waste heat in the U.S. electricity generaton sector in in operaton during the day or draw on other power 16 2017. A signifcant fracton of this is rejected at the sources—presumably grid-supplied—to operate steam cycle condenser at a temperature of roughly 40°C, contnuously. From a capital-utlizaton viewpoint, which is not directly useful for DAC. However, this may intermitent operaton reduces the overall capacity leave a substantal amount available at an appropriate of a facility to remove CO2, thus increasing the capital temperature for amine-based DAC. Industrial processes, required to build a plant achieving a given average such as refning, cement producton and aluminum removal rate. Also, ramping up and down the operaton smeltng, also generate large amounts of waste heat in of DAC would likely introduce additonal wear and tear the United States—as much as 13 quads in 2017. on components that would increase O&M costs. It is therefore no coincidence that two of the leading It may be possible to develop DAC plants with either DAC companies (Climeworks and Global Thermostat) operatonal strategies or hardware additons to beter use waste heat for regeneratng their sorbents. Per Table match an intermitent power supply. Operatonally, 1 above, these processes consume approximately 7 GJ this could include strategies where the regeneraton of of heat energy (plus a signifcantly smaller amount of the sorbent is scheduled for tmes that best match the electricity) per ton of CO2 removed, suggestng that 1 availability of curtailed power, if that can be coarsely quad of waste heat (at appropriate quality) could supply predicted (such as day-night variaton). Alternatvely, the thermal energy required to operate DAC facilites additonal equipment to provide electrical energy with a capacity of 150 MtCO2/year. While electrical storage (such as bateries) or thermal energy storage energy would stll be required and there would be (such as phase-change materials) could be used to increased capital costs from heat-exchanger surfaces, smooth the delivery of energy to the DAC facility and the scale of waste heat in terms of its potental for DAC bufer energy-supply variability, although this would is clearly very large. increase the capital cost of the facility. Although the recent Natonal Academies report However, curtailment of renewable electricity appears investgates some sources of low-carbon heat in to be a phenomenon that decreases over tme, as their cost assessment, this work represents early transmission lines are built to access stranded power consideraton of current system designs, cost and and grid operators become more adept at integratng approaches. Substantal additonal work is required as variable supplies.21 Therefore, this apparent “wasted” part of a DAC development pathway that is both low- resource may not be available to a DAC facility 17 cost and low-carbon footprint. permanently, undermining the engineering and economic logic of sitng the facility near locatons with

24 December 2018 high amounts of curtailment. A beter understanding of E. Identifying Optimal Locations for DAC the status and causes of curtailed renewables is needed Since DAC uses the atmosphere as the source gas for before pursuing any large-scale strategy of using this CO2 removal, it can in principle be located anywhere on energy source for DAC. the Earth’s surface. However, there are many practcal consideratons that limit this, and identfying the optmal D. Reducing Capital Costs Through Air locatons for DAC facilites will be important for reducing Contactor Design their costs and increasing their lifecycle CO2 removal In additon to the energy consideratons for the sorbent/ total. These can be expressed as a series of tradeofs or solvent material discussed above, the rate of the CO2 as coefcients favoring or discountng sites. The primary binding reacton is another important constraint. If consideratons are: this rate is slow, then building a system that achieves a ■ The availability of low-carbon heat and power— benchmark capacity of a certain number of tons of CO 2 partcularly waste heat as discussed above—is a removed per day would require a much larger area for high-priority consideraton for sitng. Waste heat air-sorbent/solvent contact. Conversely, if the binding must generally be immediately next to a DAC facility reacton rate is fast, this area can be reduced. A larger to be used, since it is difcult to transport, so this is contact area results directly in increased capital costs the most restrictve factor. It also directly impacts the for a DAC plant, suggestng that a fast reacton is very operatng costs, since it reduces the energy that must desirable.22 The design of an efcient air contactor must be purchased. The availability of low-carbon power therefore be based on the choice of sorbent/solvent, as depends on the fuel mix of the local grid, while the well as on its form (solid or liquid). availability of curtailed renewable power may depend The geometry and blowing/pumping strategy will on the topology of grid transmission lines. These are determine the efciency with which air contacts the both looser constraints than waste heat. They also sorbent/solvent material, the tme over which this primarily impact the lifecycle CO2 removal amount occurs and the energy required, and thus should be a rather than the operatng costs. central focus of design atenton. Additonally, while ■ CO2 oftake, transport or storage opportunites will liquid sorbents can be pumped away from the air be important in infuencing the costs, or potental contactor to a separate locaton for regeneraton, solid revenues, related to the fate of the removed CO2. sorbents must generally be regenerated in situ, which If there is an opportunity to sell the CO2 (such implies certain design constraints for the air contactor as to greenhouses) or otherwise utlize it, being and may also reduce the fracton of tme during which it located near the point at which this happens will can remove CO2. The structural materials choice for the reduce transport costs. Similarly, if the CO2 is to be air contactor is also an important determinant of capital sequestered, being located at the point of injecton cost, since this is by far the largest physical component will keep these transport costs low. If the CO2 does of the overall facility; as noted earlier, some designs need to be transported, access to a pipeline network appear to ofer signifcant cost savings by using plastc will be important. structural materials in place of steel. ■ Favorable air conditons will help minimize operatng Some loss of sorbent/solvent material to passing costs. These include (1) low levels of moisture, which air is inevitable in any real-world design, and this can lead to reducton of CO2 adsorbed because of must be taken into consideraton for understanding competton with water (unless there is a strong both operatons and maintenance (O&M) costs (for business case to produce and sell fresh water); (2) replacement) and environmental impacts (for downwind favorable air temperature (to reduce the heat energy areas). This issue is of partcular concern for caustc required to regenerate sorbents); and (3) favorable sorbents that can become entrained in passing air and winds (to reduce fan power consumpton). These are dangerous when inhaled.23 While inital reports factors will have diferent impacts on the performance from one company (Carbon Engineering) indicate this and costs of a DAC facility depending on many aspects entrainment is low for their air contactor design, it will of the system design, so these generalizatons may not require more testng to validate a variety of designs. hold under all conditons.

December 2018 25 There has been very litle research on this issue, and it G. Ensuring Net CO2 Removal from DAC would be valuable to examine the tradeofs in greater Removing CO2 from ambient air with DAC facilites may detail for diferent DAC technologies and related not result in a net reducton in CO2 concentratons if assumptons. the energy and materials requirements for removal are themselves very carbon-intensive. The most signifcant F. Demonstrating Geological Carbon instance of this is energy consumpton, as discussed Storage at Scale previously. However, emissions associated with To achieve large volumes of atmospheric producing materials, such as sorbents and structural decarbonizaton, it is likely that most DAC facilites would materials, and with supplying water could also play an be paired with disposal and storage of CO2 in deep important role in the net CO2 balance of DAC systems.28 geological formatons, usually called geological carbon Similarly, if CO2 that is removed from ambient air storage or GCS. There is a substantal scholarship on through DAC is used rather than sequestered, the GCS, and today nearly 20 large-scale facilites capture, utlizaton process may result in a lower net reducton store and monitor anthropogenic CO2.24 of CO2 concentratons or possibly in a net increase. If DAC is deployed at the gigaton scale for CO2 removal, Understanding this may be partcularly challenging in it will likely require thousands of large GCS facilites, situatons in which the DAC facility producing CO2 as a and limits on the large-scale viability of GCS would feedstock and the CO2U utlizaton process consuming limit DAC.25 This raises a set of technical, social, legal that feedstock are operated separately or partcipate in a and policy questons. Some questons (e.g., public larger CO2 producton-consumpton market mediated by acceptance) are ameliorated by DAC’s geographic a pipeline infrastructure.29 fexibility, and other concerns (e.g., environmental These concerns indicate that it will be extremely impacts of leakage) have been addressed in existng important to use Lifecycle Assessment (LCA) to assess literature, regulaton and experience. Several questons and account for all sources of emissions in the overall remain in the DAC context and, if lef unresolved, may DAC system (with associated utlizaton, if any). limit DAC volumes and deployment. This can identfy the relatve emissions implicatons Seismic risk: Although no operatng CO2 injecton facility among alternatve systems designs and help guide the has generated large earthquakes, some large-scale development of targeted RD&D programs to improve injecton projects have, mostly at geothermal or oil & gas net CO2 reductons. A key consideraton in this process brine-disposal wells. While many scholars see this risk as is understanding the longevity of CO2U products and manageable, focus on avoiding potentally risky sites will CO2 storage locatons since rapid return of CO2 to the be needed.26 atmosphere may negate most of the benefts of DAC- based removal. Long-term site care: To gain climate beneft, captured and stored CO2 must stay isolated from the atmosphere indefnitely. Technologies exist to manage and avoid H. Roadmap: Key Focus Areas For RD&D operatonal risk, and liability stays with operators during to Advance Direct Air Capture injecton. However, questons remain about how best to ■ Materials: Research is needed on the discovery, manage large GCS sites afer operaton. Some of these design, manufacture and functonalizaton of materials questons focus on technical questons of long-term that capture CO2 from the air. For sorbents, the key monitoring. Others focus on maintaining liability for an performance metrics are low regeneraton energy, appropriate length of tme. Legal and policy scholarship high CO2 selectvity, fast reacton tmes and low on the appropriate structure and mechanisms have degradaton rates. For solvents, an additonal key proposed many potental approaches that could serve performance need is liquid solutons that have lower as viable solutons.27 Untl conventonal CCS scales up heat capacity than water and comparable or lower commercially and key questons are resolved, DAC will viscosity. RD&D programs should consider approaches face these concerns. that include high-throughput materials testng, computatonal materials discovery and a focus on earth-abundant, low-cost materials.

26 December 2018 ■ Low-carbon heat: Research is needed on new and/ ■ Process designs: Research is needed on new and or improved technologies to generate renewable improved operatonal concepts for DAC, including and low-carbon heat. Both high-quality and low- optmizing heat integraton for maximum heat quality heat can serve DAC systems. In many cases recovery. A related focus should be on sorbent/ (e.g., existng nuclear fssion plants, fossil plants with solvent regeneraton cycling concepts to maximize CCS), the most valuable area of focus is recovery and equipment usage intensity and minimize equipment integraton of low-carbon heat (potentally including degradaton and material replacement requirements. waste heat). In others (e.g., concentratng solar power For batch processes, there may be opportunites to and renewable hydrogen), the focus should be on take advantage of diurnal temperature swings. Further low-cost, low-carbon energy producton. In all cases, analysis is needed to understand the value of using research should focus on systems that can scale up intermitent sources of renewable energy (partcularly and should include full lifecycle accountng. Because of those that are curtailed), and RD&D on process the rapid cost reductons and increased deployment of designs that are matched to this energy source renewable power, electricity-based technologies merit may be needed. Process concepts beyond primarily additonal atenton, including heat pumps with high temperature-swing sorpton should be considered. lif and, potentally, microwave-based heatng. ■ Environmental impacts: Research is needed on ■ Air contactors: Research is needed on improved improving the understanding of downwind impacts materials and designs for large-scale air contact with (such as entrainment of caustcs), water consumpton sorbent- and solvent-type systems. These approaches and other potental impacts. should focus on increasing contact area, while ■ System analysis: Research is needed on system minimizing pressure drop or the equivalent, to limit performance and economics, including beter energy requirements for air movement. These systems understanding of optmal locaton/sitng, tradeofs should also minimize loss of sorbent/solvent material between water producton and CO2 removal, and the and may need improved heat integraton and high value of CO2 producton at diferent purity levels. thermal conductvity.

NEAR-TERM MEDIUM-TERM LONG-TERM OPERATION AT SCALE (1 – 3 years) (2 – 8 years) (4 – 15 years) (8 – 20 years)

Develop improved sorbents Demonstrate 2 – 4 Demonstrate 1 – 2 and working fluids integrated systems at integrated systems at ktCO2 /yr scale 100 ktCO2 /yr scale Develop advanced designs for air contractors

Establish 2 – 4 reference Validate cost / tCO2 Establish full portfolio TECHNOLOGY Identify sources of systems for cost and with and without of DAC systems at renewable heat at scale performance comparisons CO2 offtake 100 MtCO2/yr

Identify primary factors Map optimal locations and relative value for for DAC facility siting; Link DAC sites to sequestration sites

LOCATIONS Validate DAC LCA for Provide ongoing integrated system at deployment support Continue development 100 ktCO2 /yr scale for DACS Identify key early of CO2U and CO2 FATE 2 markets for CO2 sequestration CO

Provide RD&D support Support pilot-scale Support large-scale of DACS demonstration projects demonstration projects POLICY

Figure 5-1. Innovaton Roadmap – Direct Air Capture.

December 2018 27 ■ Synergistc CO2 utlizaton technologies: Research 9 Concentratng solar power”, SEIA website (visited is needed on CO2 utlizaton approaches that are October 5, 2018), htps://www.seia.org/initatves/ synergistc with DAC, partcularly those that do not concentratng-solar-power. require pipeline transport and/or high purity. 10 Hardik Naik et al., “Medium temperature applicaton of concentrated solar thermal technology: Indian perspectve,” Renewable and Sustainable Energy 1 Secretary of Energy Advisory Board (SEAB) Task Force Reviews (September 2017) at p.369-78, htps://doi. on CO2 Utlizaton, Final Report (December 2016), org/10.1016/j.rser.2017.03.014. htps://www.energy.gov/seab/downloads/fnal-report- task-force-co2-utlizaton. 11 Julie K. Langenfeld et al., “Assessment of sites for CO storage and CO capture, utlizaton, and storage 2 US Nuclear Regulatory Commission, Small Modular 2 2 systems in geothermal reservoirs,” Energy Procedia Reactors website (accessed November 15, 2018), (July 2017) at p.7009-17, htps://doi.org/10.1016/j. htps://www.nrc.gov/reactors/new-reactors/smr.html. egypro.2017.03.1842. 3 NASA Radioisotope Power Systems website (accessed 12 US Department of Energy, “Improving process heatng November 15, 2018), htps://rps.nasa.gov/technology/. system performance” (2015), htps://www.energy.gov/ 4 US Dept. of Energy, “Chapter 7: Advancing Systems sites/prod/fles/2016/04/f30/Improving%20Process%20 and Technology to Produce Cleaner Fuels,” Heatng%20System%20Performance%20A%20 Quadrennial Technology Review (2015), htps:// Sourcebook%20for%20Industry%20Third%20Editon_0. www.energy.gov/sites/prod/fles/2017/03/f34/ pdf. qtr-2015-chapter7.pdf; Mathew R. Shaner et al., “A 13 IEA, “Applicaton of Industrial Heat Pumps” (2014), comparatve technoeconomic analysis of renewable htps://iea-industry.org/app/uploads/annex-xiii-part-a. hydrogen producton using solar energy,” Energy & pdf; Global CCS Insttute, “Heat pump applicatons” Environmental Science (May 2016) at p.2354-71, (website retrieved November 15, 2018), htps://hub. htps://doi.org/10.1039/c5ee02573g; Gunther Glenck globalccsinsttute.com/publicatons/strategic-research- and Stefan Rechelstein, “The prospects for renewable priorites-cross-cutng-technology/44-heat-pump- hydrogen producton,” (2017), htps://www-cdn.law. applicatons-industrial-processes. stanford.edu/wp-content/uploads/2018/04/171222_ RenewableHydrogen_fnal__1___1_.pdf. 14 Jack Browne, “Microwave energy powers many industrial applicatons,” Microwaves & RF (April 2017), 5 Global CCS Insttute, 2018, Global Status of CCS, 2018, htps://www.mwrf.com/systems/microwave-energy- htps://www.globalccsinsttute.com/status. powers-many-industrial-applicatons. 6 Lyubovsky 2017, Shifing the paradigm: Synthetc 15 US Department of Energy, “Chapter 6: Innovatng Clean liquid fuels ofer vehicle for monetzing wind and Energy Technologies in Advanced Manufacturing,” solar energy, J. of Energy Security, htp://www.ensec. Quadrennial Technology Review (2015), htps://www. org/index.php?opton=com_content&view=artcl energy.gov/sites/prod/fles/2016/06/f32/QTR2015-6I- e&id=604:shifing-the-paradigm-synthetc-liquid- Process-Heatng.pdf. fuels-ofer-vehicle-for-monetzing-wind-and-solar- energy&catd=131:esupdates&Itemid=414. 16 Lawrence Livermore Natonal Laboratory, “Estmated U.S. Energy Consumpton on 2017,” LLNL-MI-410527 7 Summers W, 2014, Baseline Analysis of Crude Methanol (April 2018), htps://fowcharts.llnl.gov/content/assets/ Producton from Coal and Natural Gas, NETL Report docs/2017_United-States_Energy.pdf. 101514, htps://www.netl.doe.gov/research/energy- analysis/search-publicatons/vuedetails?id=720. 17 Natonal Academies 2018, op. cit. 8 US Department of Energy, “Chapter 6: Innovatng Clean 18 Jan Wohland et al., “Negatve Emission Potental of Energy Technologies in Advanced Manufacturing,” Direct Air Capture Powered by Renewable Excess Quadrennial Technology Review (2015), htps://www. Electricity in Europe,” Earth’s Future (September 2018) energy.gov/sites/prod/fles/2016/06/f32/QTR2015-6I- at p. 1380-4, htps://doi.org/10.1029/2018EF000954. Process-Heatng.pdf. 19 H.A. Daggash et al., “Closing the carbon cycle to maximize climate change mitgaton: power-to-

28 December 2018 methanol vs. power-to-direct air capture,” Sustainable 25 Natonal Academies 2018, op. cit. Energy Fuels (April 2018) at p.1153-69, htps://doi. 26 org/10.1039/C8SE00061A. Ruben Juanes, Bradford H. Hager and Howard J. Herzog, “No geologic evidence that seismicity causes 20 Lori Bird et al., “Wind and Solar Energy Curtailment: fault leakage that would render large-scale capture Experience and Practces in the United States,” NREL/ and storage unsuccessful,” Proceedings of the Natonal TP-6A20-60983 (March 2014), htps://www.nrel. Academy of Sciences (December 2012) at E3623, gov/docs/fy14ost/60983.pdf; Michael Waite et al., htps://doi.org/10.1073/pnas.1215026109. “Modeling wind power curtailment with increased 27 capacity in a regional electricity grid supplying a Michael Faure, Liability and Compensaton for Damage dense urban demand,” Applied Energy (September Resultng from CO2 Storage Sites, 40 Wm. & Mary Envtl. 2016) at p.299-317, htps://doi.org/10.1016/j. L. & Pol'y Rev. 387 (2016), htps://scholarship.law. apenergy.2016.08.078. wm.edu/wmelpr/vol40/iss2/3.

28 21 Bird et al., op. cit. Patricia Luis, “Use of monoethanolamine (MEA) for CO2 capture in a global scenario: Consequences and 22 Secretary of Energy Advisory Board (SEAB) Task Force alternatves,” Desalinaton (February 2016) at p.93-9, on CO2 Utlizaton, Final Report (December 2016), htps://doi.org/10.1016/j.desal.2015.08.004. htps://www.energy.gov/seab/downloads/fnal-report- 29 task-force-co2-utlizaton. David Sandalow et al., “Carbon Dioxide Utlizaton (CO2U): ICEF Roadmap 2.0,” Innovaton for Cool Earth 23 NIOSH website, access November 15, 2018, htps:// Forum (November 2017), htp://www.icef-forum.org/ www.cdc.gov/niosh/npg/npgd0523.html. platorm/upload/CO2U_Roadmap_ICEF2017.pdf. 24 Global CCS Insttute, 2017, Global Status of CCS Report, htps://www.globalccsinsttute.com/status.

December 2018 29

control carbon dioxide emissions adequately, since CO2 Chapter 6 emiters do not bear the full costs of their emissions. Government policies are essental to provide solutons to these problems.3 Policy Considerations Meetng the goal of limitng temperature increases Policy support will be central to development of DAC, requires that cumulatve emissions from human both in the short- and long-term. This chapter discusses actvites remain within the “below 2°C budget.” Carbon the ratonale for policy support and range of policy tools removal technologies are an important part of the available. toolkit for achieving this. While reducing emissions of carbon dioxide and other greenhouse gases is a priority A. Rationale in the short-term, the Intergovernmental Panel on Climate Change and others have found that emissions Carbon Dioxide Removal reductons alone are unlikely to be sufcient. Removing The concentraton of carbon dioxide in the atmosphere carbon dioxide from the atmosphere is very likely to is now higher than at any tme in human history. be essental to achieving the goals set forth in the Paris 4 Human actvites including fossil fuel combuston and Agreement. deforestaton contnue to increase that concentraton. The impacts include devastatng heat waves, more Direct Air Capture severe and frequent storms, sea level rise, forest loss The set of policies that may be relevant to CDR and ocean acidifcaton.1 technologies is quite broad, and the appropriate policy mix is diferent for each CDR method. In DAC’s case, the Refectng this situaton, more than 175 countries have early stage of the technology means that government ratfed the Paris Agreement, which calls for “[h]olding policies should include support for RD&D. Private the increase in the global average temperature to well companies do not usually invest in the socially optmal below 2°C (3.6°F) above pre-industrial levels” and level of early-stage RD&D (whether or not there are achieving net zero emissions in the second half of this externalites involved), in part because they are unlikely century.2 to see returns within tme frames important to most The problems that arise from high levels of CO2 in corporate managers. This further emphasizes the need the atmosphere are classic “externalites,” to use the for government support of DAC RD&D.5 language of economics. Market forces alone will not

December 2018 31 Many climate-relevant technologies enter the market Some have questoned whether scarce government as compettors with well-established conventonal resources should be devoted to development of DAC technologies. Prominent examples of this include technologies, when those resources could be used for electric vehicles (which compete with ICE vehicles), other purposes.8 The authors of this report believe no renewable electricity generaton (which competes with potental pathway for reducing the threat of climate fossil and nuclear generaton), biofuel (which competes change should be ignored. While recognizing that private with gasoline and diesel) and LEDs (which compete with and governmental capital resources are fnite, achieving incandescent, fuorescent and halogen lightng). In each a 2°C (3.6°F) or 1.5°C (2.7°F) stabilizaton seems case, the new technology provides an equivalent energy impossible without a wider range of credible, actonable service to the entrenched conventonal technology. optons. Investment and support for innovaton is This means that customers—individuals, companies, essental to create those optons. DAC ofers a potentally and governments—will generally consider buying and important set of tools for mitgatng and ultmately installing the new technology only in the context of the reversing climate change. Current policy support for DAC existng market for the conventonal one. is exceedingly modest and could be increased by a factor of 10 or more without meaningfully competng with This form of market entry implies clear cost targets that support for other technologies. Especially given the long these technologies must achieve in order to deploy lead tmes required to scale DAC technologies, devotng widely without subsidies. While these technologies are resources to the development and deployment of those almost always more expensive than their conventonal technologies is strongly in the public interest.9 counterparts when they frst enter the market, RD&D and learning-by-doing can reduce their costs B. Policy Tools signifcantly.6 If these costs fall to the point that they are equal to or less than their conventonal counterparts, Very few policies around the world today specifcally market forces will generally ensure that they will be target DAC for support. The most signifcant such policy adopted. (There are additonal consideratons, such is probably in the United States, where a law enacted as compatbility with technical standards, regulatory in early 2018 provides a tax credit for direct air capture barriers, customer awareness and interoperability, that of carbon dioxide. Some governments invest small must also be considered, but these are usually less amounts in RD&D for DAC. Low carbon fuel standards important than cost.) in California, the European Union and several other jurisdictons provide incentves for DAC. DAC will follow a fundamentally diferent patern, since it does not directly compete with established technologies: Supportve policies will be essental for DAC to scale in there is no conventonal market for technologies to the decades ahead. Potental policy tools are discussed remove CO2 from ambient air at scale. Therefore, it is below. not clear what cost target would be relevant for DAC to achieve market success. In limited instances, DAC Government Support for RD&D may compete with conventonal sources of CO2, such Natonal governments spend roughly $15 billion annually as geological deposits or co-producton with ammonia.7 on RD&D for clean energy technologies. These programs However, since the overall CO2 market is relatvely small have played important roles in the development of and the end-point costs are ofen dominated by delivery countless technologies in recent decades.10 costs (as in the case of greenhouses), this does not serve Government spending on RD&D for DAC is exceedingly to establish a generally applicable cost target. modest. In 2015, the U.S. Department of Energy (DOE)’s This situaton implies that policy drivers will be required ARPA-E program ofered $3 million for RD&D on DAC. to scale DAC in a way that is signifcantly diferent than The Government of Alberta has provided grants to many climate-relevant technologies developed to date. support DAC.11 The U.K.’s Department of Business, These drivers may require a very diferent structure than Energy and Industrial Strategy supports carbon dioxide policy tools for other climate technologies and may need removal programs including DAC. Funds for these to be sustained for a relatvely long period of tme. programs are a tny percentage of overall government funding for clean energy RD&D.

32 December 2018 An increase in funding for RD&D on DAC could qualify for the credit, facilites must capture a minimum speed deployment and yield important benefts. This of 100,000 tons of carbon dioxide per year. roadmap identfes a number of priority areas for RD&D This type of tax incentve could be a model for similar investment, including: provisions in many other countries. Alternatve or ■ improved sorbent materials, additonal tax incentves could include tax-exempt debt ■ improved air contactor designs, fnancing (e.g., private actvity bonds), an investment ■ improved sources of low carbon heat, and tax credit or bonus depreciaton of capital assets, all of ■ improved CO2 utlizaton technologies which have been proposed in the U.S. Congress. In December 2015, heads of state from more than 20 Carbon Price countries announced Mission Innovaton, a coaliton A price on carbon dioxide emissions, whether through dedicated to acceleratng clean energy innovaton. an emissions trading program or tax mechanism, Member governments (including Japan, China, the provides emiters with an important incentve to cut United Kingdom, Germany and Saudi Arabia) pledged emissions. Carbon pricing programs are now in place to double RD&D on clean energy within fve years. in the European Union, Norway, California, nine States The increase in RD&D budgets from these countries in the northeast United States, the Canadian provinces in the next few years ofers an opportunity to scale of Britsh Columbia and Quebec, and seven Chinese up government RD&D funding for direct air capture, provinces. The Chinese government is in the process of including in the areas above. launching a natonwide emissions trading program for The United States helped launch Mission Innovaton and the power sector. remains a member. Although the United States is unlikely In the short-term, carbon prices are unlikely to approach to fulfll its overall doubling pledge under the Trump the cost of DAC. The lowest cost for DAC envisioned with administraton, in 2018 the U.S. Congress increased current technologies that has been publicly presented is funding for clean energy programs at DOE by roughly $94/tCO .13 Only three countries—Sweden, Switzerland 12 2 15% over the prior year. DAC has won bipartsan and Lichtenstein—currently have nominal carbon prices support in the U.S. Congress and could be an area in that exceed that amount. Most carbon prices are much which the government’s RD&D spending increases in the lower (below $25/tCO2).14 However, even a low carbon years ahead. price can create incentves for DAC by contributng to Tax Incentives project revenues. In additon, the prospect of a price on carbon may help incentvize private sector investments in Tax incentves can play an important role in helping research and development on DAC, if market partcipants spur development of clean energy products. In Norway, expect the price to increase in the medium- to long-term. for example, generous tax incentves helped plug-in electric vehicles capture 39% of new car sales in 2017. A carbon price could provide signifcant incentves for Such incentves could play a similar role in promotng direct air capture, if emiters receive credit for tons development and deployment of DAC. of CO2 removed with DAC. Indeed, a carbon price is an important part of any long-term strategy for Legislaton providing a tax incentve for DAC was enacted DAC. Although DAC can provide carbon dioxide for in the United States in early 2018. Known as the FUTURE commercial purposes, it is unlikely to be the lowest-cost Act or “45Q” (for the provision of the U.S. Tax Code it source for doing so, except perhaps in remote locatons. amends), the law provides a tax credit of $28-50/tCO2 A price on carbon emissions is likely to be a central part captured from the air and stored in saline aquifers. of the ratonale for many, if not most, DAC facilites. (The $28 credit is available in 2018 and increases $2-3 per year, reaching $50 by 2026.) The law also provides Low-Carbon Fuel Standard a tax credit of $17-35/tCO2 captured from the air and A low-carbon fuel standard (LCFS) sets a limit on the used for enhanced oil recovery or converted into carbon dioxide emissions of transportaton fuels useable products. (The $17 credit is available in 2018 throughout their lifecycle. California, Oregon, Britsh and increases $2-3 per year, reaching $35 by 2026.) To Columbia and the European Union (E.U.) have all

December 2018 33 enacted low-carbon fuel standards and the Canadian There may be instances in which government mandates federal government is developing a natonal system.15 could help build DAC scale. As one opton, governments California’s LCFS requires producers of petroleum-based could require that a certain percentage of the CO2 used fuels to reduce the carbon intensity of their fuels 10% in enhanced oil recovery (EOR) be provided by DAC. from 2010 levels by 2020 (state regulators are currently This could create a substantal market for CO2 from DAC. considering a 20% by 2030 requirement.) The E.U.’s Fuel (EOR is one of the largest commercial markets for CO2 Quality Directve requires reductons of 6% in the carbon today.) It could also help reduce the carbon footprint intensity of fuels from 2010 levels by 2020. of EOR.19 At present, DAC may be too expensive and unproven for such a requirement to be considered in Fuels made with carbon dioxide from DAC, all else being many jurisdictons. As DAC technologies mature and fall equal, have a lower carbon intensity than fuels made in price, however, such mandates might be more likely to with carbon from fossil fuels. An LCFS therefore incen- be adopted. tvizes DAC, providing a potental market for the carbon dioxide DAC produces. The more stringent the LCFS, the greater the incentve.16 The California LCFS includes a Government Procurement process to gain credit through applicaton of a lifecycle In many countries, government procurement makes analysis under a regulated protocol. Similarly, existng fuel up more than 10% of GDP.20 Government purchases standards like the U.S. Renewable Fuel Standard or the can play an important role in startng and building European Renewable Diesel Standard could be expanded new product markets. First, government purchase to account for fuels produced using DAC. contracts can provide developers and manufacturers of new products with an assured market, which can be Finally, DAC can be interpreted to fall within the purview especially important in securing debt capital. Second, of fuel standards as a pathway to reduce fuel emissions government purchases can help establish standard post-combuston from the air and ocean. The recent technical specifcatons for new products, which can help revisions to the California LCFS do this explicitly and catalyze efcient supply chains. ofer DAC creditng for projects without geographic restricton. Under the revised rulemaking, DAC with Governments could spur development of DAC geological storage must comport with the other aspects technologies using procurement authorites. For of the CCS protocol to be credited. example, governments could target CO2-based fuels for procurement, with a preference for CO2 from DAC. (The Mandates U.S. Navy has had a similar program for the purchase of drop-in biofuels.21) Similar procurement authorites Governments mandates can be efectve in helping build could be applied to CO -based plastcs, concrete or other markets for clean energy products. In the United States, 2 synthetc building materials. As DAC technologies mature, many state governments require utlites to purchase a governments could play a powerful role in developing the minimum percentage of their power from renewable technology with their procurement power. sources. In India, a similar requirement is imposed by the Ministry of New and Renewable Energy. These requirements have been important to the early growth Lifecycle Assessments. of wind and solar power in both countries.17 Lifecycle assessments (LCAs) are essental for evaluatng the climate benefts of direct air capture. If the power Other experiences suggest cauton, however. A U.S. and heat used in a DAC process come from zero-carbon federal government mandate has required the use of sources, the climate benefts will be considerable. If the cellulosic ethanol in fuel supplies for almost a decade. power and heat used in a DAC process come from high- Nevertheless, the cellulosic ethanol industry remains carbon sources, the climate benefts could be negatve. in its infancy and waivers to that requirement have been granted on a regular basis. Technology-forcing Governments can help develop and standardize LCA requirements—in which governments require private methodologies for DAC, in part to facilitate GHG actors to meet standards that are not yet technically accountng methodologies and protocols. Government achievable—have been successful in some instances but agencies, such as the U.S. Natonal Insttute of Standards not in others.18

34 December 2018 and Technology (NIST) or U.S. Department of Energy 7 Hans A. Haugen et al., “Commercial Capture and (through its natonal labs), can fund work by experts, Transport of CO2 from Producton of Ammonia,” convene relevant stakeholders and issue guidelines Energy Procedia (July 2017) at p.6133-40, htps://doi. org/10.1016/j.egypro.2017.03.1750; Kinder Morgan based on the inputs received. Governments can also website (accessed November 15, 2018), htps://www. incorporate LCAs into their work on DAC, requiring that kindermorgan.com/pages/business/co2/supply/supply. DAC projects be carbon negatve on a lifecycle basis aspx. to meet any regulatory requirements or to qualify for 8 See, e.g., Kevin Anderson and Glen Peters, “The government support. Trouble with Negatve Emissions,” Science (October Related to this, CDR should be considered for inclusion 2016) at p.182-3, htp://science.sciencemag.org/ in internatonal GHG accountng standards, which content/354/6309/182. would likely require additonal work in quantfying and 9 See generally htps://www.vox.com/ validatng CDR volumes for diferent pathways and energy-and-environment/2018/6/14/17445622/direct- approaches.22 air-capture-air-to-fuels-carbon-dioxide-engineering 10 A wide range of policy tools are available for supportng See Mission Innovaton website at htp://mission- DAC. Government policies—in partcular one that puts innovaton.net/our-work/baseline-and-doubling-plans/ a price on carbon—are likely to be central to the growth 11 See, e.g, “Opportunity: Capture CO2 from low and long-term role of the technology. concentraton-coal industry,” FedConnect (July 2015), 12 htps://www.fedconnect.net/FedConnect/default. 1 IPCC Working Group II, “Climate Change 2014: aspx?ReturnUrl=%2fFedConnect%2f%3fdoc%3d Impacts, Adaptaton and Vulnerability—Summary DE-FOA-0001342%26agency%3dDOE&doc=DE- for Policymakers” at p.13, htp://www.ipcc.ch/pdf/ FOA-0001342&agency=DOE; Noah Deich, Direct assessment-report/ar5/wg2/ar5_wgII_spm_en.pdf. 3. Air Capture Explained in 10 Questons (September

2 2015), htp://www.centerforcarbonremoval.org/ Paris Agreement Artcle 2(1)(a), htps://unfccc.int/ blog-posts/2015/9/20/direct-air-capture-explained-in- sites/default/fles/english_paris_agreement.pdf; Paris 10-questons. Agreement Artcle 4(1), htps://unfccc.int/sites/default/ fles/english_paris_agreement.pdf. 13 Umair Ifran, “Trump wanted to slash funding

3 for clean energy. Congress ignored him,” Vox See Sir Nicholas Stern, Stern Review on the Economics (March 2018), htps://www.vox.com/energy- of Climate Change (2006), htp://webarchive. and-environment/2018/3/22/17151352/ natonalarchives.gov.uk/+/htp://www.hm-treasury.gov. omnibus-energy-environment-trump. uk/sternreview_index.htm. See also Alison Benjamin, “Stern: climate change a market failure” Guardian 14 David Keith et al., “A Process for Capturing CO2 from (November 29, 2007) (quotng Sir Nicholas Stern the Atmosphere,” Joule (August 2018) at p.1573-94, –"Climate change is a result of the greatest market htps://www.sciencedirect.com/science/artcle/pii/ failure the world has seen”), htps://www.theguardian. S2542435118302253?via%3Dihub. com/environment/2007/nov/29/climatechange. 15 See World Bank and Ecofys, “State and Trends carbonemissions. of Carbon Pricing” (May 2018) at p.11, htps:// 4 IPCC, op. cit. openknowledge.worldbank.org/bitstream/

5 handle/10986/29687/9781464812927.pdf; “Countries See Robert Stavins, “Repairing the R&D Market Failure,” with the highest carbon price,” Carbon Pulse Environmental Forum (Jan/Feb 2011), htps://scholar. (September 2016), htps://www.carbonbrief.org/ harvard.edu/fles/stavins/fles/column_40.pdf; Kenneth mapped-countries-with-highest-carbon-price. Gillingham and James Sweeney, “Market Failure and the Structure of Externalites” (July 2008), htp:// 16 Gov. of Canada, 2018, Clean Fuel Standard environment.yale.edu/gillingham/GillinghamSweeney_ (website), htps://www.canada.ca/en/environment- MktFailureStructureExternalites_proof.pdf. climate-change/services/managing-polluton/

6 energy-producton/fuel-regulatons/clean-fuel- Edward S. Rubin et al., “A review of learning rates standard.html. for electricity supply technologies,” Energy Policy (November 2015) at p.198-218, htps://doi. 17 See Mat Lucas, “The $150+ Per Ton Incentve for org/10.1016/j.enpol.2015.06.011. Carbon Capture Nobody is Talking About,”

December 2018 35 18 (August 2018), htps://www.centerforcarbonremoval. 21 See generally Greg Cooney et al., “Evaluatng the org/blog-posts/2018/8/21/the-150-per-ton-incentve- Climate Benefts of CO2-Enhanced Oil Recovery Using for-carbon-capture-nobody-is-talking-about; Dave Life Cycle Analysis,” Environmental Science and Roberts, “Sucking carbon out of the air won’t solve Technology (May 2015) at p.7491-500, htps://pubs. climate change,” Vox (July 2018), htps://www.vox.com/ acs.org/doi/pdf/10.1021/acs.est.5b00700; Global energy-and-environment/2018/6/14/17445622/direct- CCS Insttute, “Enhanced Oil Recovery results in air-capture-air-to-fuels-carbon-dioxide-engineering. signifcant net CO2 emissions reducton,” (September 2016), htps://www.globalccsinsttute.com/news/ 19 See Tom Kenning, “Revision to ‘single most important insttute-updates/iea-enhanced-oil-recovery-results- policy’ to drive solar ready for approval,” PV Tech signifcant-net-co2-emissions-reducton. (November 2015), htps://www.pv-tech.org/news/ intersolar-india-revision-to-single-most-important- 22 Esteban Ortz-Ospina and Max Roser, “Public Spending” policy-to-drive-solar-re. (2017), htps://ourworldindata.org/public-spending/. 20 See generally David Gerard and Lester Lave, 23 U.S. Energy Informaton Administraton, “Biofuels are “Implementng Technology-Forcing Regulatons,” included in latest U.S. Navy fuel procurement,” (July Technological Forecastng and Social Change 2014) (September 2005) at p.761-78, htp://faculty.lawrence. 24 Royal Academy of Engineering, Greenhouse Gas edu/gerardd/wp-content/uploads/sites/9/2014/02/18- Removal (2018), ISBN: 978-1-78252-349-9, htps:// TFSC-Gerard-Lave.pdf. www.raeng.org.uk/publicatons/reports/greenhouse- gas-removal.

36 December 2018 Recommendation 1: Chapter 7 Governments around the world should begin RD&D on direct air capture today.

Findings and FINDING 3: By its intrinsic nature, DAC can play a major and distnct Recommendations role in deployment of CDR. DAC is a concentrated Direct air capture (DAC) lies at one end of the carbon process requiring a small physical footprint. It uses dioxide removal (CDR) spectrum and could play an earth-abundant materials, and its removal operaton is important role in limitng the increase of atmospheric straightorward to quanttatvely measure. The capacity CO2 concentratons. The potental scale of deployment of DACS (DAC with sequestraton) to remove CO2 is is very large. Today, DAC technologies exist, but their quite large and is limited primarily by cost, energy costs, energy inputs and thermal requirements are very requirements and geological storage capacity. RD&D high. These fndings summarize key components of eforts can reduce costs and energy requirements, while this roadmap and distll a set of recommendatons for geological storage capacity is estmated to be many consideraton. trillions of tons. For these reasons, DAC plays a role as the “backstop” technology on the cost curve for climate FINDING 1: strategies. Although DAC faces specifc challenges (see Large-scale CDR will likely be essental to achieve below), including those related to geological CO2 storage, the goal of preventng a global average temperature it has important potental as a CDR technology and as a increase of 2°C (3.6°F) above pre-industrial levels. means to produce CO2 as a feedstock. The overwhelming majority of integrated assessment models, including 87% of the IPCC models, fnd that CDR FINDING 4: is required to achieve a 2°C (3.6°F) target. In additon, a The key limits to DAC are costs. Because CO2 is more substantal number of current published assessments of dilute in the atmosphere than in emissions sources such the global carbon budget suggest that a CDR is required as fue gas, more energy is required to separate and today to avoid both overshoot and the associated concentrate it. On this basis, DAC will almost certainly consequences of anthropogenic global warming. always cost more than conventonal CCS on most power plant and heavy industrial sources. The costs FINDING 2: of DAC include both the capital costs and operatonal There are many engineered and natural pathways to costs, including very low-carbon or zero-carbon heat achieve large-scale CDR, including DAC. These pathways and power. Current costs are difcult to estmate and include reforestaton and aforestaton, increasing soil vary by locaton and technology; nonetheless, today’s carbon uptake, bio-energy with CCS (BECCS), enhanced DAC technologies appear to operate at $300-600/tCO2 weathering and DAC. Each approach has challenges, removed. including technical readiness, cost, resource availability and social acceptance. Many have additonal economic FINDING 5: or environmental benefts. Overall, a full portolio of Innovaton can play an immediate and substantal role optons has the greatest chance of success and the in reducing costs and improving performance of DAC lowest risk of failure. Unfortunately, most governments approaches. The feld of DAC is very young. Today’s have not yet formally recognized the likely necessity devices are far from the limits of thermodynamics, and of CDR, and very few have commited to programs both fundamental research and applied engineering supportng CDR.

December 2018 37 are likely to produce signifcant cost reductons. It FINDING 8: appears likely that costs could be reduced to less than There are many policy optons that could support $200/tCO by 2025 and less than $100/tCO by 2030. 2 2 DAC deployment and CDR more broadly. As a frst However, accomplishing this would require a sustained step, governments could recognize DAC as part of a investment in focused RD&D. portolio of CDR optons, essental to important climate outcomes. They could invest in innovaton and research, Recommendation 2: as well as procure both DAC services and materials made Direct air capture programs should include from atmospherically derived CO2. They could provide fundamental research, applied science and scale-up. incentves for deployment of DAC technology (e.g., the These programs should include research on new recent inclusion of DAC into the California Low Carbon CO2 solvents and sorbents, low-carbon heat and Fuel Standard). They could support lifecycle analyses other topics. The program goals should focus on and industrial standards. Furthermore, for DAC to play reducing the cost of DAC, in part by deploying DAC a major role in a broader CDR portolio, it will likely be units to foster learning-by-doing. DAC should be paired with geological CO2 storage, which faces policy incorporated into conventonal CO2 storage projects issues around permitng, long-term care, liability and as part of an RD&D agenda where possible. social acceptance. FINDING 6: Private sector policies mater as well. Companies could add DAC to their emissions reducton strategies, both Enough companies and technologies exist today for by deploying the technology and buying low-carbon and rapid progress in DAC cost-reducton and scale-up. negatve-carbon materials made with DAC-derived CO2. Today, three companies ofer DAC devices and services with a clear expectaton of performance. Many more Recommendation 3: companies and innovators have begun work on Governments, industry and fnancial insttutons alternatve designs and approaches. In additon, many should work together to scale up direct air capture. other new technologies (e.g., additve manufacturing, Policies to promote DAC should include investment materials discovery and supercomputng) have the in RD&D, government procurement, targeted potental to dramatcally improve cost and performance incentves, standard-setng, work on lifecycle for DAC but have not yet been applied to that goal. analyses and recogniton of DAC in carbon markets. FINDING 7: DAC provides some additonal benefts beyond atmospheric separaton and concentraton of CO2. Some DAC approaches have a co-beneft of freshwater separaton. All approaches could help support the manufacturing of goods from CO2 (e.g., fuels, plastcs, cement), and may ofer a market diferentaton of value in that way.

38 December 2018 Final Thoughts The movie Apollo 13 includes several scenes that feature too much CO2 in the space capsule, promptng a direct air capture. Afer a malfuncton in the space reassessment of priorites and a change of mission. capsule endangers the mission, NASA scientsts on the Crucial to the success of that mission and to sustaining ground in Houston quickly realize that the CO2 scrubber the lives of the crew, the technology already exists to in the capsule is damaged and requires modifcaton resolve the issue. Innovaton is required, and teams of to functon. Without the scrubber, CO2 concentratons scientsts and decision makers learn rapidly. This allows in the capsule of the spacecraf will exceed safe limits the team to survive with their limited resources during and the crew will die. A team gathers around a large their trip through space. The government had to assign worktable and dumps out a handful of gadgets and substantal resources on the ground and learn through objects, the few expendable and spare parts on board acton to fnd a soluton. the spacecraf that could be used to fashion a working The growing concentraton of CO2 in the atmosphere is air-capture device. Afer 75 minutes, they fnd a soluton also an urgent threat. With resolve and determinaton and coach the astronauts on how to modify their existng like that showed by those who saved Apollo 13, we can technology to return the CO levels in the air to safe 2 meet the threat. (To quote the movie’s most famous line: levels. “Failure is not an opton.”) Large-scale carbon dioxide These scenes serve as a metaphor as we face the removal will likely be essental in the global response to threat of climate change. In these scenes, a sudden climate change. Direct air capture of CO2 could be an environmental challenge has become urgent, with important part of the soluton.

We are deeply grateful to the Ministry of Economy, Trade and Industry (METI) and New Energy and Industrial Technology Development Organizaton (NEDO), Japan, for launching and supportng the ICEF Innovaton Roadmap Project of which this is a part.

December 2018 39