Enduring reduction of carbon and nitrogen emissions from landfills due to aeration?

The objective of the present work is to investigate to what extent emission reductions observed during landfill aeration are permanent. To do so, lab-scale degradation experiments using waste from an old landfill have been conducted under different conditions (anaerobic, (partly) aerobic returning to anaerobic, aerobic) and balances for carbon and nitrogen have been established. For the latter, all emissions of C and N (except N) and their pools at the start and end of the experiment have been determined. In addition, the chloroform fumigation-extraction method (biocidal treatment) has been applied to determine microbially bound carbon and to estimate nitrogen in microbial biomass accordingly. The results reveal that 18 g TOC·kg DM of the waste material were mineralized during aerobic treatment for 699 days, which is equivalent to about 14% of the initial TOC content. For the anaerobic treatment, only 10 g TOC·kg DM were released. For the aerobic-anaerobic reactors, a slight increase in methane emissions approximately 10 months after termination of aeration was observed. With respect to leachate emissions, the results indicate significantly lower emission levels (factor 1.5 for TOC and factor 4 for TN) for the reactors, which were aerated at least sometimes. The biocidal treatment highlights that this emission reduction is rather based on an increased sorption capacity of aerated waste (higher ion exchange capacity) than a lower overall pollutant potential. It is shown that regardless of the operation mode, most nitrogen remained in solids (83.1-92.6%) and is subject to internal recycling during waste degradation.