Material flows and Embodied Energy of Direct Air Capture

Direct air capture (DAC) is an essential nexus of CO2 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 paramterized modelling of life cycle inventories of distinc 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 modelled. 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 DAC often lies in the range or above the formation energy of CO2 (8.94 GJ energy can be obtained by formation of 1t CO2 from elementary C and O2). This indicates that theoretically more energy is required for capture, as can be obtained during the formation of CO2. 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 sheds light on real opportunities for direct air capture 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.