Evidence of stabilized peat as a net carbon sink

Mass stabilization, a ground improvement solution used for construction in peatlands, involves mixing suitable dry binders into the peat, increasing strength and stiffness and reducing permeability. A previous pilot study of the carbonation process in stabilized peat showed that it could be a net sink of CO₂, because the binder takes in CO₂ from the atmosphere and any CO₂ released by oxidized peat due to carbonation. In this study, a closed-chamber method was applied to stabilised peat specimens over a 6 month period to assess the factors affecting CO₂ intake rate. The studies revealed that an increase in cement content and a larger surcharge contributed to a larger CO₂ intake rate. These rates decreased logarithmically with time, and surcharge was found to be less influential over time. The CO₂ intake rate reduced when the atmospheric CO₂ concentration reduced, and the replacement of cement with ground granulated blast-furnace slag had a negative effect on the CO₂ intake rate due to its lower carbonation potential. Furthermore, a high water table resulted in a decrease in the CO₂ intake rate. These laboratory results have highlighted that dry soil mixing has a minimal on-site impact in environmental terms, allowing geotechnical engineers to make more informed decisions on the suitability of this technique for construction projects.