Biological Carbon Sequestration Strategies: A Case Study on Microbial Exopolysaccharides in Arid Soils

Abstract

The rising atmospheric CO₂ levels, driven by human activities such as fossil fuel consumption and land degradation, have increased the need for effective and sustainable carbon sequestration strategies to mitigate climate change. Biological carbon sequestration (BCS) has emerged as a promising approach, leveraging natural processes in ecosystems to capture and store atmospheric carbon. However, the current literature on carbon sequestration is divided—while some studies highlight its potential benefits, others point out limitations or negative impacts. This conflicting evidence reveals the need for a deeper understanding of the true effectiveness and challenges of these strategies. The thesis therefore begins with a comprehensive review of existing biological carbon sequestration methods, covering a range of strategies across multiple domains, including soil-based approaches, microbial pathways, land management practices, and ocean and wetland systems. Through this review, major gaps in current research are identified, for instance, most of current research has completely neglected the role of soil carbon equilibrium in effective long term carbon sequestration. The potential of arid and semi-arid lands, which are far below the carbon equilibrium, is often overlooked. The reason for that being traditional approaches struggle to achieve effective carbon sequestration in such regions due to harsh environmental conditions, such as poor soil quality, mechanics and water retention and extreme weathers. These constraints underscore the urgent need for innovative solutions to improve soil stability, water retention, and carbon storage in such environments.

Microbial exopolysaccharides (EPS) are a relatively underexplored yet promising pathway for enhancing soil stability. The experimental component of the study represents an initial step towards this ambitious goal by investigating the potential of microbial exopolysaccharides (EPS) as a novel strategy to stabilize sands and enhance their water interactions. The project focuses on evaluating the role of EPS produced by Komagataebacter medellinensis strains in improving the physical and mechanical properties of arid sandy soils. The research investigates both in-situ EPS growth and ex-situ bacterial cellulose (BC) sheet layering techniques to assess their impact on soil cohesion, mechanical strength, and water retention. We compare the effectiveness of these two approaches in reinforcing soil structure and improving water permeation. These insights offer new avenues for enhancing soil restoration efforts thereby enhancing carbon sequestration potential in challenging arid environments, contributing to the broader goal of mitigating the effects of climate change through nature-based solutions.

Date of Award	23 Dec 2024
Original language	American English
Supervisor	Blaise Tardy (Supervisor)