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

Applying the 15N labelling technique to material derived from a landfill simulation experiment to understand nitrogen cycle processes under aerobic and anaerobic conditions

“…Investigating the aerobic–anaerobic reactors on day 753 the gross consumption rates declined slightly (but remained higher than for the aerobic group) to 20.1 ± 2 mg N (kg DM day) −1 , whereas net mineralization remained stable at around − 10 ± 4.5 mg N (kg DM day) −1 . The final measurement for the aerobic–anaerobic reactors is supported by two other observations: the steady increase in NH 4 -N concentration in leachate to 24 mg L −1 and the increase in microbial biomass (Fricko et al 2021 ). At the experimental start, gross ammonium production rates were determined for the anaerobic reactors, which exceeded gross ammonium consumption, resulting in positive net mineralization (an ammonium release) of 23.8 ± 14.4 mg N (kg DM day) −1 .…”

“…Although the individual measurements between the groups differed strongly, for all of these reactors and all sampling campaigns, gross consumption of ammonium exceeded gross production (mineralization), thus resulting in a net removal of ammonium. The highest rates for both groups were observed at the beginning of the experiment (day 0) and before the start of aeration (day 54), which also represents the period of highest biodegradation (highest carbon turnover, Fricko et al 2021). This observation reveals that there is a large potential for the consumption of ammonium during this period, which corresponds well with the decline in leachate NH 4 -N concentrations from 604 ± 22 to 0.40 ± 0.04 mg L −1 within 14 days after the start of aeration.…”

“…As the detailed design and a schematic diagram of the LSRs has already been published (Fricko et al 2021 ), only the most important facts will be presented in this study. The reactors contained a total volume of 60 L; however, only about 40 L were initially filled with MSW.…”

“…The three exceptions are explained easily: Nitrate concentrations are expected to increase during the aeration of old MSW landfills. However, with a remarkably long delay (Brandstätter et al 2015 ; Fricko et al 2021 ). Hence, only for the completely aerobic reactors at the very end of the experiment did nitrate concentrations reach a value high enough for direct labeling of the pool instead of spiking.…”

“…The field application of in-situ aeration is, in many cases, combined with lab-scale studies (Hrad et al 2013 ; Ritzkowski et al 2016 ) utilizing landfill simulation reactors (LSR) to quantify the emission reduction achievable. Results from such studies (Brandstätter et al 2015 ; Fricko et al 2021 ) indicate that most of the nitrogen remains in the solid phase. This somehow contrasts with the observed decline in ammonium concentrations in the leachate.…”