Techno-economic assessment of coupling direct air capture with formic acid value chain in buildings under different scenarios

• Techno-economic study of a novel carbon capture and utilization chain in buildings. • The potential of this chain is investigated under ten different scenarios. • Direct air capture’s energy performance is assessed against controlled ventilation. • Conversion of captured CO 2 to formic acid is the costliest phase in the studied route. • Generating electricity from formic acid is not cost-effective in all scenarios. Carbon capture and utilization (CCU) is emerging as a promising pathway that could play a key role in enhancing the sustainability of buildings. However, the energy performance and economic feasibility of this route under different conditions remain uncertain. To address this research gap, this study provides a techno-economic assessment of a novel CCU value chain within buildings, consisting of capturing indoor CO 2 via a direct air capture (DAC) system and converting the captured CO 2 into formic acid (FA) through an electrochemical CO 2 reduction reaction (ECO 2 RR). The produced FA is designed to be sold to the market or converted into electricity using direct formic acid fuel cells (DFAFCs) as an electricity backup solution. The energy and cost efficiencies of this value chain are evaluated under ten distinct scenarios, considering varying levels of energy needs, carbon tax, capital and operating costs, as well as electricity and FA market prices. The results show that DAC has great potential in improving indoor air quality, but the energy requirements are 21–27% higher than conventional controlled ventilation, resulting in levelized costs of DAC of 56–259 $/tCO 2 , depending on the considered scenarios. Furthermore, it is observed that the ECO 2 RR is the costliest step in the studied value chain with a levelized cost of FA of 1.01–1.26 $/kgFA. In contrast, the conversion of produced FA into electricity via DFAFCs results in a levelized cost of electricity of 1.38–2.10 $/kWh, requiring innovation in DFAFC technology for widespread deployment in buildings. In this vein, implementing a carbon tax, providing clean and affordable energy, and lowering the overall cost of the investigated CCU chain demonstrate promising results for enhancing its economic viability. These outcomes can be used by investors, urban planners, and building owners as a guide to determine the conditions under which the explored value chain will be economically viable.