Mitigating long-term emissions of landfill aftercare: Preliminary results from experiments combining microbial electrochemical technologies and in situ aeration

Landfills still represent the main option for waste disposal in many parts of the world. Anyway, they often pose a significant pollution risk and contribute to potential environmental and human health impacts via gaseous and liquid (leachate) emission pathways if not properly managed. Some innovative technologies can help to reduce these emissions, such as in situ aeration and the application of microbial electrochemical technologies (METs). METs are an emerging field that open the possibility to control microbial reactions, enhancing electron flows from electron donors towards electron acceptors. To this end, several materials with different electrochemically-active properties are used, such as electrical conductivity, capacitance, surface electroactivity and charge. The present project named LA-LA-LAND (Landfill electron-Lapping for a LANDscape requalification) was aimed to apply METs to treat leachate-saturated zones in old landfills. A MET prototype was constructed using a granular anode (graphite) and a cylindrical air-cathode (electroactive biochar). The METs were integrated to three identical laboratory-scale landfill bioreactors coupled with the in situ aeration technique, while three control reactors run without MET. The maximum values of current and power density obtained were 0.015 A·m^-2 and 0.00035 W·m^-2. The influence of the MET system on the organic matter removal was evident in two reactors, where this technology was applied, with respect to the control ones: total organic carbon decreased on average 13%, while it reduced less than 5% in the control reactors. This preliminary experiment pointed out some critical aspects of MET configuration, such as the weakness of the cathode architecture, which was prone to be flooded by leachate, blocking the aeration flux.