Thesis Defence: Life cycle-based environmental and economic sustainability assessment of enzyme-induced calcite precipitation (EICP) and microbially-induced calcite precipitation (MICP) biocementation

Yu Sun, supervised by Dr. Sumi Siddiqua, will defend their thesis titled “Life cycle-based environmental and economic sustainability assessment of enzyme-induced calcite precipitation (EICP) and microbially-induced calcite precipitation (MICP) biocementation” in partial fulfillment of the requirements for the degree of Master of Applied Science in Civil Engineering.

An abstract for Yu Sun’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Please email sumi.siddiqua@ubc.ca to receive the Zoom link for this defence.

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Abstract

Rural development and wildfires disrupt local vegetation and soil structures, reducing bearing capacity, which can lead to landslides and water contamination, especially on slopes. Conventional methods enhance structural integrity by replacing problematic soil with heavy machinery and replacing it with compact materials such as cement and gravel. While effective, this process is resource-intensive and emits a significant amount of pollutants due to the production and transportation of ordinary Portland cement and pit-run gravel. Alternatives like microbially induced calcite precipitation (MICP) and enzyme-induced calcite precipitation (EICP) provide in- situ stabilization, improving existing materials and decreasing resource use, waste, and carbon emissions with suitable applications. However, studies on the environmental and economic sustainability of these technologies remain limited. This study evaluates the life cycle sustainability of two alternative soil stabilization methods. A life cycle assessment (LCA) based on the ISO 14040/44 for environmental sustainability and life cycle costing for economic sustainability is used for evaluating MICP and EICP throughout their life cycles. The software OpenLCA is used for conducting LCA. The findings show that the production of bacteria and enzymes in raw materials largely contributes to environmental impacts, especially in large-scale soil treatment. Additionally, this study developed a comprehensive and integrated framework that combines Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and Multi-Criteria Decision Analysis (MCDA) using TOPSIS, a multi-criteria decision analysis evaluation is used to aggregate environmental and economic factors. EICP is found to be the most sustainable method while prioritizing environmental weight. Higher sustainability makes EICP an ideal solution for environmentally friendly rapid soil stabilization in wildfire-affected areas where low-strength reinforcement and intermediate-term stabilization are needed.