Life cycle assessment (LCA) is a systematic and science-based approach used to evaluate the environmental impacts of a product, service, or process over its entire life cycle, from the extraction of raw materials to the end of its useful life, including disposal. This study focuses on the CO2 emission from the Silica Fume (SF)-based geopolymer treated organic soil. The SF-based geopolymer is made by adding an external source of alumina, obtained from pure aluminum oxide (Al2O3). The samples were prepared by taking both binders (SF + Al2O3) in the percentages of 10, 20, and 30% by weight of dry organic soil. These binders were activated by NaOH with molarities of 3, 6, and 9, and alkali/binder ratios were chosen as 0.5, 0.7, and 0.9. The result shows that the CO2 emission increases with alkali/binder ratio, binder content and alkali content. Further, the Carbon Index (CI) values were also evaluated which showed that at 6 and 9 Molarity the CI value is low which infers better sustainability of the geopolymer treated soil.