Long-term impacts of in-situ aeration on landfill stabilization: An Austrian case study

In-situ aeration is a widely recognized method for stabilizing waste in old landfill sites, aiming to reduce the aftercare phase, lower greenhouse gas emissions (especially methane), and mitigate environmental risks. While its immediate effects are well-documented, the long-term sustainability of its outcomes, particularly longer periods after the shut-down of an aeration-plant, remains underexplored. This study investigates the long-term impacts of in-situ aeration at an Austrian landfill site, utilizing monitoring data collected over a decade after the cessation of the aeration process and following the implementation of a final cover. The findings demonstrate that the positive effects of in-situ aeration persist, with reduced pollutant concentrations in leachate-particularly for ammonium nitrogen (NH₄-N), biochemical oxygen demand over 5 days (BOD₅), and the BOD₅/COD ratio-meeting suggested stability thresholds compared to pre-aeration levels. Notably, annual substance loads meet all stability criteria, largely due to the final cover installed in 2016, which limited water infiltration, reduced leachate generation, and enhanced the containment of residual emissions. Furthermore, methane (CH₄) emission assessments, based on surface CH₄ concentrations, revealed minimal emissions, with no significant levels being detected during the final monitoring sessions, underscoring the lasting benefits for greenhouse gas mitigation. These results demonstrate that in-situ aeration, combined with appropriate post-aeration measures such as final cover installation, is effective in bringing landfills to a state of low current emissions and reduced future emission potential.