Material flows and embodied energy of direct air capture: A cradle‐to‐gate inventory of selected technologies

Abstract

Direct air capture (DAC) is an essential nexus of CO 2 chemistry and climate mitigation. Life cycle assessment (LCA) is often used to validate the environmental potential of emerging technologies. Consequently, an increased number of ex ante LCAs is expected in this field. However, a comprehensive description through parameterized modeling of life cycle inventories of distinct technological pathways, which is essential for transparency, has recently been missing from the international literature. To fill this gap, the present study analyzes three selected DAC technologies to create an inventory. Amine-based adsorption and absorption, as well as alkali-based absorption, were modeled.The energy consumption of the operation, cradle-to-gate embodied energy, and sensitivity analysis based on parameter variations were carried out. The "cradle-to-gate" energy requirement of direct air capture (DAC) often lies in the range or above the formation energy of CO 2 (8.94 GJ energy can be obtained by formation of 1 t CO 2 from elementary C and O 2 ). This indicates that theoretically more energy is required for capture, as can be obtained during the formation of CO 2 . Because energy has continuously growing economic and ecological value, this energy intensity of DAC implies that DAC might have important role in CCU to add directly measurable economic value.The parametrized model includes over 60 parameters, resulting in an array of possible energy and material requirements. The use of this wide range of figures in life cycle assessment (LCA) sheds light on real opportunities for DAC in future product systems.The option of varying parameters enables the tailoring of the calculation to a particular situation or design. In this way, the calculator offers a common base for LCA, fostering an early stage analysis of DAC technologies.

Solar-Powered Direct Air Capture: Techno-Economic and Environmental Assessment

“…Due to the gas-fired calciner used in conventional L-DAC, there is a clear source of fossil CO 2 that is correctly identified and accounted for in the literature, as the cost is typically reported per ton of CO 2 removed from the atmosphere (LCOD) rather than per ton of CO 2 produced (LCOP). ,, However, the available techno-economic assessments of conventional L-DAC do not consider the compensation of indirect GHG emissions, which have already been identified in several environmental assessments. ,− This simplification may have led to more optimistic LCODs for conventional L-DAC. Similarly, it is of great importance to quantify the indirect emissions of solar-powered L-DAC in order to compensate for them.…”

“… 3 , 4 , 23 However, the available techno-economic assessments of conventional L-DAC do not consider the compensation of indirect GHG emissions, which have already been identified in several environmental assessments. 7 , 75 − 77 This simplification may have led to more optimistic LCODs for conventional L-DAC. Similarly, it is of great importance to quantify the indirect emissions of solar-powered L-DAC in order to compensate for them.…”

Prospective environmental burdens and benefits of fast-swing direct air carbon capture and storage

“… The replacement frequency was shortened from 3 years to 1 year, resulting in a comparable sorbent consumption as Climeworks of 3.5 kg/ton CO 2 15 . Additionally, a sorbent lifetime of 5 years is investigated to showcase the extremes 44 . Varying the sorbent material performance, the total capture capacity was halved and multiplied by 1.5.…”