Direct CO2 Capture and Utilization for Climate Change Mitigation Through Building HVAC systems: A Sustainability Assessment

Abstract

Anthropogenic CO2 emissions are rising rapidly, requiring urgent mitigation. In addition to reducing emissions, negative emission technologies are needed to remove CO2 from the atmosphere and offset hard-to-avoid sources such as transport and industry. One such technology is Direct Air Capture (DAC), which can support climate change targets but is limited in scalability due to its energy-intensive nature. Integrating DAC technology with heating, ventilation, and air conditioning (HVAC) in buildings has been proposed to address these challenges. This study explores DAC-HVAC-based carbon capture and utilization (CCU) systems focusing on their efficiency, scalability, and economic viability. Life cycle assessment (LCA) studies are performed on different CCU pathways. The impacts for the DAC-HVAC integrated unit are notably lower, 15% less than standalone DAC systems. For the electrochemical reduction of CO2 to formic acid, the required electricity for the operation of the electrochemical cell was found to have the highest impact on the climate change category, accounting for 96% of the overall emissions. LCA is performed on formic acid production and Fisher-Tropsch using captured CO2 from DAC-HVAC. The environmental performance of a high-tech greenhouse utilizing CO2 captured from DAC-HVAC is also evaluated. It was shown that significant reductions in emissions can be achieved by integrating renewable energy sources into these processes. A comprehensive economic and life cycle costing analysis is also performed for DAC-HVAC, Formic acid production and greenhouse utilization. In addition, an exposure-response model is developed to link indoor CO2 levels and cognitive performance applied to an office building to assess occupant health impacts from DAC-HVAC. The study underscores the environmental, economic and health benefits of DAC-HVAC integration and CCUS systems, demonstrating their potential to simultaneously address climate change, energy and food security and occupant well-being. This research is a significant contribution to global initiatives toward a more sustainable, carbon-neutral future. The findings from this study can help researchers, policymakers, and industrial stakeholders make critical decisions regarding material selection and optimization to improve the sustainability of these processes.

Date of Award	2026
Original language	American English
Awarding Institution	HBKU College of Science and Engineering