Figure 10.2: Pathways for GHG emissions from landfills and wastewater systems:
Figure 10.2a: Simplified landfill CH4 mass balance: pathways for CH4 generated in landfilled waste, including CH4 emitted, recovered and oxidized.
Note: Not shown are two longer-term CH4 pathways: lateral CH4 mitigation and internal changes in CH4 storage (Bogner and Spokas, 1993; Spokas et al., 2006) Methane can be stored in shallow sediments for several thousand years (Coleman, 1979).
Figure 10.2b: Overview of wastewater systems.
Note: The major GHG emissions from wastewater – CH4 and N2O – can be emitted during all stages from sources to disposal, but especially when collection and treatment are lacking. N2O results from microbial N cycling under reduced aeration; CH4 results from anaerobic microbial decomposition of organic C substrates in soils, surface waters or coastal zones.