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The optimization of degradation processes and the management of leachate and biogas produced in landfills are key aspects for the establishment of more sustainable municipal solid waste (MSW) disposal in developing countries. In this study, biochemical methane potential (BMP) tests were used to evaluate CH 4 production potential and degradation kinetics of fresh waste (FW) and five-year aged excavated waste (EW) samples from a tropical controlled landfill with compositional characteristics of developing countries. BMP tests with reconstituted samples of the biodegradable fraction of both MSW types were performed at three substrate/inoculum (S/I) ratios (0.3, 0.5 and 1.0 g VS substrate g − 1 VS inoculum), and CH 4 generation parameters were determined using the first-order and modified Gompertz kinetic models. After 30-d, the best BMP results were reached at S/I ratios of 0.5 and 1.0, with cumulative CH 4 productions of 528 and 433 mL CH 4 g − 1 VS for FW, respectively; and 151 and 135 mL CH 4 g − 1 VS for EW, respectively. The first-order kinetic model provided a good fit to BMP results for FW, whereas the modified Gompertz model showed a better adjustment to the BMP data for EW. Calculated first-order CH 4 generation rates for FW and EW were in the range 0.19-0.36 and 0.23-0.25 d − 1 , respectively. These results evidence the high biodegradability and CH 4 potential of FW disposed of in a tropical landfill in Colombia and the reduced BMP of EW despite a relatively short period after disposal under conventional landfill operation conditions.

This study evaluated leachate recirculation (LR) as a stabilisation strategy for landfills using bioreactor experiments with excavated waste from a tropical landfill in Colombia. The experimental evaluation was performed in two 115 L bioreactors, one simulating the operation of a landfill with LR, Br2, where the leachate produced was recirculated at a rate of 0.8 L d−1, and a control system without LR, Br1. Both systems reached stabilisation indicator values on a dry matter (DM) basis for volatile solids VS (<25% DM) and a biochemical methane potential BMP (≤10 mL CH4 g−1 DM). Likewise, towards the end of the experiment, the leachate generated in Br2 reached stabilisation indicator values for BOD5 (<100 mg L−1) and the BOD (biological oxygen demand)/COD (chemical oxygen demand) ratio (<0.1). Although the stabilisation criterion for COD was not met in any bioreactor (<200 mg L−1), LR helped to release 19% more oxidisable organic matter in Br2 than in Br1, indicating a reduction in the contaminating potential of the waste in the case of uncontrolled discharges of leachate to the environment. Regarding biogas production, the generation of CH4 in Br2 was more intense and its cumulative production was 34.5% higher than Br1; thus, Br2 achieved CH4 emission rates, indicating waste stabilisation (<1.0 L CH4 m−2 h−1) sooner than Br1, showing an accelerating effect of LR on waste degradation. A carbon mass balance indicated that waste degradation, in terms of the initial total organic carbon mineralisation and the C gas discharge via CH4, was greater in Br2. These results demonstrate the LR potential to accelerate the stabilisation of a landfill but also to reduce greenhouse gas emissions in final disposal sites where biogas is also captured and utilised for energy production; a key aspect when improving the sustainability of landfill operations in developing countries.

Landfilling is still the most common technology used in developing countries for the final disposal of municipal solid waste (MSW), albeit the negative impacts on the environment such as those caused by the release of greenhouse gases (GHG) that contribute to global warming (GW). The Colombian government set a target of 20% reduction in GHG emissions by year 2030, for which the solid waste management sector has an important role to play. Also, the achievement of the targets of sustainable development goals (SDG) is playing a key role for the government agenda and will do so for the next years. In this context, there is an important room for improvement of the management alternatives in currently operative landfills in the country, especially in terms of measures to reduce fugitive air emissions and leachates. This paper evaluates, using life cycle assessment (LCA) methods, the environmental impacts associated with a landfill in Colombia under four different scenarios: open dumps (zero) and conventional landfill under three landfill gas (LFG) management alternatives: venting (a), flaring (b), and energy recovery (c). The impact categories as well as the life cycle impact assessment