Carbon dioxide reduction from an intensive green roof through carbon flux observations and energy consumption simulations

Green roofs have the potential to reduce carbon dioxide directly through photosynthesis and indirectly through building energy savings. Most previous studies either focused exclusively on the direct or indirect CO₂ reduction of GRs, resulting in an incomplete assessment. A comprehensive assessment of the CO₂ reduction potential of GRs would aid in promoting their use as carbon credits in the carbon trading market. This study quantifies the total CO₂ reductions from a newly built intensive green roof with yearlong carbon flux observations and building energy simulations. Our results indicate that direct and indirect carbon reductions from IGR significantly differ, with the monthly direct and indirect CO₂ reduction ratio ranging from 1:5 to 1:130. Direct and indirect CO₂ reduction exhibits significant seasonal trends, with peak direct reduction in autumn and peak indirect reduction in summer. Overall, the total annual CO₂ reduction from this IGR system is 4355.6 g CO₂·m⁻², of which 46.6 g CO₂·m⁻² and 4309 g CO₂·m⁻² were direct and indirect, respectively. Further research should evaluate the long-term integrated carbon reduction over the life cycle of the GRs. The findings of this study could provide evidence to leverage GRs as a nature-based solution to achieve net-zero carbon emissions.