Life Cycle Assessment of an Integrated Direct Air Carbon Capture and Utilization System

Abstract

This article presents a thorough life cycle assessment (LCA) study on carbon capture and utilization (CCU) systems for low-carbon fuel production. The process involves capturing carbon dioxide (CO₂) from indoor environments using an integrated heating, ventilation, and air conditioning (HVAC)—direct air capture (DAC) unit, a technology crucial for mitigating climate change (CC). Integrating DAC with HVAC systems is highlighted for its potential to enhance energy efficiency and indoor air quality. Electrochemical reduction of CO₂ to formic acid (FA) and Fischer–Tropsch processes are studied for carbon utilization. A sensitivity analysis was performed on the adsorbent type, electricity source, and water source. The environmental impacts were found to be 1.80 kg CO₂ eq, 9.04 × 10⁻⁴kg PM2.5 eq, 1.04 × 10⁻⁵kg P eq, 2.95 × 10⁻³ kg SO₂ eq, 0.36 kg 1,4 DB eq. for CC, fine particulate matter, freshwater eutrophication, terrestrial acidification, and terrestrial ecotoxicity, respectively, per kg FA produced. Using renewable energy can significantly lower the environmental impacts; the lowest value was obtained from integration with nuclear energy at 0.496 kg CO₂ eq/kg FA. A specific Qatar case study was also performed for FA production with CO₂ utilized from DAC-HVAC. The paper highlights the environmental benefits of CCU, emphasizing its dual purpose of addressing CC and sustainable fuel production. This study represents a significant contribution to global initiatives for a more sustainable and carbon-neutral future.