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Solid & Hazardous Waste Management
Sanitary Landfills & Landfill Gas
Landfill phases, leachate, gas generation and the engineered containment of municipal waste.
PART 1
Topic Breakdown & Traps
The Engineering Principle
A sanitary landfill isolates waste from the environment with a liner, leachate collection, gas extraction and a final cover. Buried waste decomposes through aerobic → acidogenic → methanogenic phases; the stable methanogenic phase generates landfill gas (≈ 50 % CH₄, 50 % CO₂), a usable energy source and a greenhouse hazard. Leachate — contaminated liquid — must be collected and treated.
The Core Formula Matrix
Phases: I aerobic → II acid (anaerobic) → III methanogenic → IV maturation.
Landfill gas: roughly 50 % CH₄ + 50 % CO₂ (by volume) at the methanogenic phase.
Gas yield: .
Liner + leachate collection: prevents groundwater contamination.
Landfill gas: roughly 50 % CH₄ + 50 % CO₂ (by volume) at the methanogenic phase.
Gas yield: .
Liner + leachate collection: prevents groundwater contamination.
The ‘IIT Traps’
- ⚠Methane (~50 %) is the energy and explosion/GHG concern, not CO₂.
- ⚠Leachate is liquid, landfill gas is the gaseous product — don't confuse them.
- ⚠Methanogenesis is anaerobic and follows the acid phase, not the first phase.
📚 Standard references
- Integrated Solid Waste Management — Tchobanoglous, Theisen & Vigil · Landfills
PART 2
Progressive 3-Tier Question Suite
Q1MEDIUM2 Marks · NAT
2000 kg of decomposable waste yields 0.15 m³ of landfill gas per kg. The total gas generated is _____ m³.
Q2BASIC1 Mark · MCQ
The principal combustible component of landfill gas, valuable for energy recovery, is:
Q3HARD1 Mark · MCQ
Sustained generation of methane in a sanitary landfill occurs during the: