Life-Cycle Assessment of a Regulatory Compliant U.S. Municipal Solid Waste Landfill

Landfills
receive over half of all U.S. municipal solid waste (MSW)
and are the third largest source of anthropogenic methane emissions.
Life-cycle assessment (LCA) of landfills is complicated by the long
duration of waste disposal, gas generation and control, and the time
over which the engineered infrastructure must perform. The objective
of this study is to develop an LCA model for a representative U.S.
MSW landfill that is responsive to landfill size, regulatory thresholds
for landfill gas (LFG) collection and control, practices for LFG management
(i.e., passive venting, flare, combustion for energy recovery), and
four alternative schedules for LFG collection well installation. Material
production required for construction and operation contributes 68–75%
to toxicity impacts, while LFG emissions contribute 50–99%
to global warming, ozone depletion, and smog impacts. The current
non-methane organic compound regulatory threshold (34 Mg yr–1) reduces methane emissions by <7% relative to the former threshold
(50 Mg yr–1). Requiring landfills to continue collecting
LFG until the flow rate is <10 m3 min–1 reduces emissions by 20–52%, depending on the waste decay
rate. In general, for landfills already required to collect gas, collecting
gas longer is more important than collecting gas earlier to reduce
methane emissions.