Methane and nitrous oxide emissions from shallow windrow piles for biostabilisation of municipal solid waste

Shallow windrow piles were applied as a low-cost option for biostabilisation of municipal solid wastes (MSW) prior to their utilization as refuse-derived fuel (RDF). A considerable amount of greenhouse gas (GHG) emissions can be emitted during the biostabilisation of MSW, especially when in operation under high moisture conditions such as there are in tropical Asia. This study investigated the emission of methane (CH₄) and nitrous oxide (N₂O) from shallow windrow piles - with heights of 0.5-1.0 m - for the stabilization of MSW at a full-scale facility in Thailand. Measurements of CH₄, CO₂, and N₂O emissions using the static-chamber method revealed high spatial heterogeneity characteristics in all zones with different waste ages. Peak methane emissions were observed after four months of biostabilisation. The average spatial methane emissions from the waste piles ranged from 7.33 to 26.88 g m^-2 d^-1 (14.86 g m^-2 d^-1, on average). The CH₄ generation-rate constant was within the range of 3.3 to 4.0 yr^-1, which is higher than that reported - about 2.20-3.50 yr^-1 - from a deep windrow pile (3.5-4.0 m height). The spatial distribution of N₂O emissions was in the range of 4.51-199.14 mg N₂O t^-1dry wt.d^-1 (6.6-111.7 mg N₂O m^-2 d^-1), similar to those previously studied from landfill operations. This shallow windrow pile technique can be applied as low-cost technology for biostabilisation of MSW in developing countries, where land area is available.Implications: Shallow windrow pile was applied as a low-cost option for biological treatment of municipal solid waste in developing countries where land area is available. This study evaluated the greenhouse gas emission characteristics during the operation of windrow pile. The findings suggest that the emission rates were varied spatially with waste ages in different zones. Higher methane generation rate constant was derived from shallow window pile as compared to deep windrow pile. The methane and nitrous oxide emission factors were derived.