Reduction of methane in landfills after postclosure period

Closure of landfills does not stop decomposition of biodegradables, resulting in continuous production of leachate and landfill gas. The EU landfill directive mandates to monitor and manage the landfills for at least 30 years post-closing the landfills. However, how to manage methane emission after this monitoring period ends? Biological degradation of gas offer attractive alternative to reduce methane emission. There are three major challenges where scientific community could help the landfill owners and regulatory body: the design of such system; the selection of substrate, and the monitoring system, to ensure that the whole system remains operational. The materials used in biofilters such as biowaste compost, wood chips, etc. supports the growth of methanotrophic bacteria, which biologically degrade methane into carbon dioxide and water. The project becomes circular, if the material for biofilters were waste-based. In Tallinn, Estonia, the Pääsküla landfill has passed the after-care period, where gas-to energy was feasible. The decision was made to replace the active gas collection system with biofilters. In 2024, six biofilters were built. Selection of materials and monitoring of the filters was a duty of Estonian University of Life Sciences. After several lab experiments, a composition of 70% scarp yard compost and 30% mineral soil was selected. Preliminary results from the ongoing stage will be shown in the current presentation. In Baltic countries, there are approximately 1400 closed landfills that require monitoring. Given the fact that Baltic countries have almost similar climate conditions, but also financial and cultural background, our work on reducing residual methane emissions in closed landfills would be beneficial and worth following for all the Baltic countries.