Environmental Sustainability Assessment of Geosynthetic Clay Liners (GCLs)

This paper presents an analysis of the performance of mineral barriers used for the environmental management of landfills and the containment of potentially polluting areas. Geosynthetic clay liners, consisting of bentonite embedded between layers of geomembrane and geotextile, offer a number of advantages including flexibility, ease of installation and good performance under high saturation conditions due to their semi-permeable membrane properties. A comparative analysis was carried out between geosynthetic clay liners and compacted clay liners with the aim of assessing the environmental sustainability of the two solutions through a Life Cycle Assessment (LCA). The study initially focused on three main process steps and calculated their carbon footprint (CF): - The extraction of raw materials in the case of Compacted Clay Liners and the production of geosynthetics in the case of Geosynthetic Clay Liners; - The transport of materials from the extraction or production site to the landfill construction site; - The construction of the liner system and the final cover of the landfill are the final stages of the landfill construction process. The atmospheric emissions from the above stages were compared with the emissions calculated after assessing the diffusive flow of gas through the landfill cover to the atmosphere.This evaluation aimed to assess the overall environmental impact. The CO₂ emissions associated with each stage and the emissions from the liner to the outside of the landfill were analysed in detail to understand the differences between the different stages of the process. The results indicate that the use of geosynthetic clay liners results in a reduction in total GHG emissions compared to compacted clay liners. This is due to lower material consumption during the construction phase, ease of installation, expedient and cost-effective transport and the effective ability to retain the flow of greenhouse gases such as carbon dioxide or methane generated within the landfill. In addition, the effectiveness of the two design solutions was assessed in terms of the release of contaminant fluxes in solution across the bottom barriers. This involved investigating the role of osmotic efficiency, as exemplified by the Geosynthetic Clay Liners, in influencing the outcome, thereby enabling the calculation of tonnes of contaminants released to the aquifer and their impact on categories such as Water Pollution Potential. The use of Geosynthetic Clay Liners (GCLs) has proven to be an effective solution for the containment of waste materials. This is largely due to the semi-permeable membrane behaviour of bentonite, which limits the migration of ions and blocks their flow. Despite their reduced thickness, GCLs offer a viable alternative to traditional compact clay solutions, providing equivalent or better performance with a reduced environmental impact.