Comparative Life Cycle Assessment of Renewable Activated Carbon Technologies

Activated carbon (AC) is a critical material in water treatment systems.It has high surface area and porosity, which allows the effective removal of organic pollutants, heavy metals, and a variety of other contaminants.However, conventional AC production primarily relies on fossil-based feedstocks like coal.Therefore, it carries substantial environmental impacts, including high greenhouse gas (GHG) emissions, water use, and energy-related impacts.Given the growing need for sustainable alternatives, renewable activated carbon (RAC) technologies and the regeneration of spent AC have arisen as promising ways to reduce environmental impacts through the use of renewable feedstocks and circular resource use.This thesis addresses the existing gap in the environmental comparison of conventional, renewable, and regenerated AC technologies.Through life cycle assessment (LCA), the study evaluates seven case studies encompassing industrial to laboratory scale systems, with feedstocks ranging from coal to sewage sludge and spent AC.A cradle-to-gate system boundary was used to quantify and compare the impacts of each system with emphasis on climate change and water use impact categories.Interpretations focused on feedstock origin, activation methods, and regional production contexts.The results reveal that conventional AC (i.e., coal-AC) shows high environmental impacts, with a climate change value of 8 kg CO₂-eq per kg AC and a water use value of 1 m³ world eq deprived per kg AC.However, some RAC systems, such as those based on sludge and wheat straw, also show significant impacts.Their climate change values are 12 and 11kg CO₂-eq per kg AC, respectively, while their water use values reach approximately 5 m³ world eq deprived per kg AC for both.However, scale of the cases and process related uncertainties should be considered while comparing the impacts results.These impacts are particularly evident in cases involving inefficient processing or high chemical inputs.As a result, spent AC and coconut AC demonstrated the lowest overall environmental impacts, highlighting their potential as a circular solution.These scenarios were followed by coal-AC, sawdust-AC and Biomethane-AC respectively.Regional sensitivity analyses further emphasised the importance of clean electricity and localised conditions in reducing environmental impacts.This thesis concludes that feedstock selection, along with production efficiency and process optimisation contexts, is key for minimising the environmental impacts caused by AC production.These findings provide practical insights for industry stakeholders and policymakers in their choices.Ultimately, it aims to promote more sustainable treatment technologies.