Material flows and Embodied Energy of Direct Air Capture

Abstract

: Direct air capture (DAC) is an essential nexus of CO2 chemistry and climate mitigation. Life cycle assessment (LCA) is often deployed to validate the environmental potentials of such future emerging technologies. Consequently, an increased number of ex-ante LCAs are expected in this field. However, recently a comprehensive life cycle inventory for LCA is missing from the international literature, which is essential for transparency. To fill this gap, the present paper analyses three selected DAC technologies to create an inventory for LCAs. Amine-based adsorption and -absorption, as well as, alkali-based absorption was modelled. Energy consumption of the operation, the cradle-to-gate embodied energy and sensitivity analysis based on parameter variations were carried out. The maximum energy released by the formation of CO2 (8.94-18.2 GJ/t CO2) were also considered in the evaluation. However several studies state that DAC is a negative emission technology, its energy requirement often lies in the range or above the formation energy of CO2. Accordingly, theoretically more energy is required for the capture as can be obtained during the formation of CO2. The calculation model includes over 60 parameters resulting in an array of the possible energy and material requirements. The use of this wide range of figures in life cycle assessment sheds light on the real opportunities of direct air capture in future product systems. The option of varying parameters enables tailoring the calculation to a particular situation or design. In this way, the calculator offers a common base for LCA fostering the early-stage analysis of DAC technologies.