(Georgia Institute of Technology, 2020-12-07)
Chhabra, Jayati
There is enough scientific consensus that anthropogenic climate change is a reality of our times. According to a report from the National Academies of Sciences, Engineering 2019, “By mid-century, the world needs to be removing about 10 billion metric tons of carbon dioxide out of the air each year. That’s equivalent of about twice the yearly emissions of the U.S.” To achieve this goal, the act to cease the emission of greenhouse gases (GHGs) alone is not enough. It is important that the structures which cover a large area of the earth start contributing to Carbon Sequestration (the process of capturing carbon from the atmosphere and storing it securely) at a massive scale. To accomplish that, a thorough understanding of building-integrated Carbon Sequestration techniques, including their mechanism, prerequisites as well as consequences, is essential.
This study aims to 1) Provide an overview of building-integrated Carbon Sequestration (CS) techniques focusing on their potential environmental impact and associated costs. CS techniques are classified into three categories: a) Biotic techniques (vertical greenery systems (VGS), Green Roofs, and algae facades); b) Materials (carbon-negative and carbon-absorbing building materials); and c) Equipment (filter towers). 2) Conduct a comparative analysis specifically showing both the CS potential and design factors associated with the Biotic CS techniques to allow architects and designers to evaluate these technologies and analyze their integration potential in architectural practice based on both the factors. 3) Propose a modeling framework to estimate the amount of carbon that can be sequestered by a structure that utilizes biotic elements to enhance environmental performance. The proposed workflow accounts for site and climate-based variations in solar radiation across the globe, as well as different plant types, species, the type of photobioreactors in the case of micro-algae, and their energy conversion efficiency ratios.
Preliminary literature review shows that Green Roofs and vertical gardens can capture 150gC/m2 – 650gC/m2, while algae facades go up to 2430gC/m2 - 2970gC/m2. Biomass and filter towers could absorb a relatively high amount of approximately 1 x 1015 g C and 687.5 x 109 g C, respectively (without normalization). By analyzing and summarizing each CS technique based on performance indicators like prerequisites, initial and maintenance costs, and area required, various schematic design considerations and research gaps are laid out. Further, the proposed modeling framework showcases the CS potential of the three biotic techniques in the context of five major Koppen classified climate zones – tropical, dry, moderate, continental, and polar. The workflow for algae facades is validated against measured data from collected information in practice from the BIQ house in Germany and Photo.synth.etica by EcologicStudio. A workflow is formulated specifically for Green Roofs and VGS from previously published literature by (Getter et al. 2009), (Whittinghill et al. 2014), (Pulselli et al. 2014), and (Kuronuma et al. 2018). This thesis presents a framework to employ CS integration in the built environment and discusses advances needed in order for buildings to not just limit the catastrophic effects of climate change, but also mitigate it for a better future for our built environment.