The technological and economic prospects for CO2 utilization and removal

Abstract

processes. Biological or land-based forms of CO 2 utilization can generate economic value in the form of, for example, wood products for buildings, increased plant yields from enhanced soil carbon uptake, and even the production of biofuel and bio-derived chemicals. We use this broader definition deliberately; by thinking functionally, rather than narrowly about specific processes, we hope to promote dialogue across scientific fields, compare costs and benefits across pathways, and consider common techno-economic characteristics across pathways that could potentially assist in the identification of routes towards the mitigation of climate change. In this Perspective, we consider a non-exhaustive selection of ten CO 2 utilization pathways and provide a transparent assessment of the potential scale and cost for each one. The ten pathways are as follows: (1) CO 2-based chemical products, including polymers; (2) CO 2-based fuels; (3) microalgae fuels and other microalgae products; (4) concrete building materials; (5) CO 2 enhanced oil recovery (CO 2-EOR); (6) bioenergy with carbon capture and storage (BECCS); (7) enhanced weathering; (8) forestry techniques, including afforestation/reforestation, forest management and wood products; (9) land management via soil carbon sequestration techniques; and (10) biochar. These ten CO 2 utilization pathways can also be characterized as 'cycling', 'closed' and 'open' utilization pathways (Fig. 1, Table 1, Supplementary Materials). For instance, many (but not all) conventional industrial utilization pathways-such as CO 2-based fuels and chemicals-tend to be 'cycling': they move carbon through industrial systems over timescales of days, weeks or months. Such pathways do not provide net CO 2 removal from the atmosphere, but they can reduce emissions via industrial CO 2 capture that displaces fossil fuel use. By contrast, 'closed' pathways involve utilization and nearpermanent CO 2 storage, such as in the lithosphere (via CO 2-EOR or BECCS), in the deep ocean (via terrestrial enhanced weathering) or in mineralized carbon in the built and natural environments. Finally, 'open' pathways tend to be based in biological systems,

An air CO2 capture system based on the passive carbonation of large Ca(OH)2 structures

“…The overall cost estimation of this DAC scheme is between 140 and 340 $ per tCO 2 captured, which is considerably less (subject to contingencies) than that of other competing DAC technologies. Flat plate thickness, m z CaCO 3 Thickness of the carbonated product layer, m 3 1 Volume fraction between stacks 3 2 Volume fraction between plates 3 Ca(OH) 2 Porosity of the Ca(OH) 2 layer 3 CaCO 3 Porosity of the CaCO 3 layer Dppmv CO 2 Reduction in the CO 2 concentration, ppm r Ca(OH) 2 Ca(OH) 2 molar density, mol m À3 r CaCO 3 CaCO 3 molar density, mol m À3…”

“…44,53-55 Fig. 3 shows the evolution with time of the carbonated layer in a Ca(OH) 2 -based solid according to eqn (2) for different values of Ca(OH) 2 solid porosity, 3 Ca(OH) 2 , and assuming a ppmv CO 2 gradient of 400 ppm (C CO 2 ¼ ppmv CO 2 /(RT Â 10 6 ) in mol m À3 ) between the external surface and the carbonation front. As can be seen, individual Ca(OH) 2 solids of thickness 5 mm (assuming 3 Ca(OH) 2 ¼ 0.5) would require around 15 days to approach total carbonation.…”

“…Direct CO 2 capture from air (DAC), combined with permanent CO 2 storage, is one of the negative emission technologies (NETs) that may be needed in the future to limit global warming to 1.5 C. 1,2 The rst conceptual designs of DAC systems were proposed 20 years ago, 3 and research into novel concepts and materials is still continuing today. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The direct capture of CO 2 from air requires vast contacting surfaces with a great affinity and selectivity towards CO 2 (i.e.…”

“…37 If CO 2 was used for the production of synthetic fuels with renewable energy, this would only lead to a maximum of 50% CO 2 captured, 38 which might be insufficient in future scenarios demanding negative emission technologies. 2 The DAC concept shown in Fig. 2 is based on the known tendency of porous Ca(OH) 2 solids to slowly carbonate in contact with ambient air.…”

From CO2 to Bioplastic – Coupling the Electrochemical CO2 Reduction with a Microbial Product Generation by Drop‐in Electrolysis

“…Due to its key role as promotor of climate change via atmospheric accumulation, especially the greenhouse gas CO 2 should be considered as a new raw material in the future. [1][2][3][4] Thereby, the focus lies on processes that enable the chemical activation of the thermodynamically stable CO 2 using regenerative energy sources and convert it into storable and uncritical substances that can serve as starting materials for higher quality products. In this context, electrochemical processes offer the option to convert electricity originating from renewable energies directly into long term storable chemical energy.…”