Greenhouse gas emissions from landfill leachate treatment plants: A comparison of young and aged landfill

•Young and aged leachate works accounted for 89.1% and 10.9% of 33.35 Gg CO2 yr−1.•Fresh leachate owned extremely low ORP and high organic matter content.•Strong CH4 emissions occurred in the fresh leachate ponds, but small in the aged.•N2O emissions became dominant in the treatment units of both systems.•8.45–11.9% of nitrogen was removed as the form of N2O under steady-state.

With limited assessment, leachate treatment of a specified landfill is considered to be a significant source of greenhouse gas (GHG) emissions. In our study, the cumulative GHG emitted from the storage ponds and process configurations that manage fresh or aged landfill leachate were investigated. Our results showed that strong CH4 emissions were observed from the fresh leachate storage pond, with the fluxes values (2219–26,489 mg C m−2 h−1) extremely higher than those of N2O (0.028–0.41 mg N m−2 h−1). In contrast, the emission values for both CH4 and N2O were low for the aged leachate tank. N2O emissions became dominant once the leachate entered the treatment plants of both systems, accounting for 8–12% of the removal of N-species gases. Per capita, the N2O emission based on both leachate treatment systems was estimated to be 7.99 g N2O–N capita−1 yr−1. An increase of 80% in N2O emissions was observed when the bioreactor pH decreased by approximately 1 pH unit. The vast majority of carbon was removed in the form of CO2, with a small portion as CH4 (<0.3%) during both treatment processes. The cumulative GHG emissions for fresh leachate storage ponds, fresh leachate treatment system and aged leachate treatment system were 19.10, 10.62 and 3.63 Gg CO2 eq yr−1, respectively, for a total that could be transformed to 9.09 kg CO2 eq capita−1 yr−1.