Page 352 - Materials Chemistry, Second Edition

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The Sanitary Landfill 323

FIGURE 10.17 (continued)

Gas
Interior burner
recovery well Blower
To gas utilization Blower Test
system Exterior probe
recovery well
Recovery well
Monitoring
probes

(a) (b)

FIGURE 10.18 Gas recovery systems for active landfill gas removal: (a) interior wells; and (b) perimeter wells
(U.S. EPA, 1994).

Generally, landfills closed for less than 5 years are ideal for energy recovery because of their con-
tent of relatively fresh and moist MSW. With time, the ability of a landfill to generate gas decreases.
Under optimum conditions, a landfill might produce gas for 15 years or more, depending on the rate
of gas generation, the water content of the waste, and the manner in which the landfill was closed.
Current closure requirements for landfills are intended to restrict the entry of moisture into the land-
fill. These requirements will lead to greatly reduced gas generation after closure.