When landfills heat up unexpectedly, the results can be disruptive – and dangerous. Elevated Temperature Landfills (ETLFs) are landfill sites where internal temperatures rise significantly above normal operating ranges (>55°C), often exceeding 80°C (176°F). These are not landfill fires, but the result of complex chemical and biological reactions deep within the waste mass that can lead to increased gas production, odors, structural instability, and high levels of leachate.
EREF is working to better understand why ETLFs form, how to detect them early, and what can be done to prevent or mitigate their impacts.
Why Does It Matter?
Elevated temperatures in a landfill:
- Damage gas collection, leachate, and liner systems
- Accelerate waste settlement and threaten slope stability
- Increase leachate strength and volume
- Suppress methane production
- Cause odorous emissions and operational difficulties
Understanding how and why these conditions form is key to prevention and control.
Chemical Drivers
Certain wastes react with moisture and CO₂, releasing heat:
- Salt dissolution and other mineral reactionsAsh hydration and carbonation: Reactions of coal ash and MSW ash with moisture and CO₂ can release significant heat.
- Metal corrosion: Especially aluminum and iron, can undergo oxidation and corrosion that is highly exothermic.
- Salt dissolution: Some reactions are endothermic but still play a role in the heat balance.
These reactions are especially intense in ash-rich or aluminum-laden waste streams.
Microbial Shifts
Elevated temperatures disrupt the normal anaerobic decomposition that produces methane:
- Under ETLF conditions, normal anaerobic decomposition breaks down.
- Methanogens are suppressed while thermophilic and sulfur/iron-metabolizing microbes increase.
- The presence of antibiotics and microplastics can further destabilize microbial communities.
Together, these processes create a feedback loop that amplifies heat and degrades landfill performance.
| Feature | Normal Landfill | ETLF |
|---|---|---|
| Temp | < 55°C | 80–100+ °C |
| Gas Output | Methane-rich | Lower CH₄, higher CO₂, H₂, VOCs |
| Waste Decomp. | Mostly anaerobic | Mixed or disrupted pathways |
| Settlement | Gradual | Rapid, uneven |
| Leachate | Moderate | High volume, higher strength |
| Odor | Minimal | Sulfides, VOCs, strong odorants |
What You Need to Know
Elevated temperatures rarely arrive without warning. These are the early indicators that a landfill may be trending toward ETLF conditions:
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Spike in gas well temperatures
Sudden increases above 55°C signal abnormal activity underground. -
Drop in methane (CH₄) levels
Indicates disruption of normal anaerobic decomposition. -
Increased CO₂, hydrogen (H₂), carbon monoxide (CO), or VOCs
Suggests chemical reactions and microbial shifts are underway. -
Strong, persistent odors
Often sulfuric or sour, due to disrupted gas pathways or new microbial byproducts. -
Accelerated waste settlement
Unusual or rapid differential settlement can compromise slope stability. -
Leachate volume spikes or chemistry changes
More leachate, higher temperatures, or higher concentrations of metals and sulfides.
If you’re seeing two or more of these symptoms, it’s time to investigate further.
To understand ETLF behavior, it’s not enough to track just temperature. You need to see the whole heat system — from cause to consequence.
Modeling the Heat
EREF-supported research developed two powerful models:
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Batch Reactor Model: Evaluates how specific waste types (like ash or aluminum) generate heat.
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3D Finite Element Model (FEM-3DM): Simulates waste placement, landfill layering, and how heat moves through the landfill over time.
Both models help operators predict problem zones, assess risk scenarios, and develop smarter acceptance strategies.
Tools That Work
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Fiber-Optic Temperature Sensing (FODTS) for real-time thermal profiling
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Vibrating Wire Transducers (VW) to monitor in-situ pressure
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Gas composition monitoring (CH₄/CO₂/H₂/VOCs) for early chemical indicators
Smart data means smarter decisions. Modeling heat behavior helps prevent costly surprises.
How to Prevent ETLFs
Avoiding thermal buildup starts with understanding your inputs.
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Know what’s in your waste stream. Screen for high-risk materials like:
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Coal or MSW ash
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Auto shredder residue (ASR)
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Aluminum-rich materials
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Test before you accept. Use calorimetry to measure heat generation potential.
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Pre-treat if needed. Hydrate ash before burial to eliminate one major source of heat.
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Limit co-disposal of reactive materials with organics.
Managing the Problem
If elevated temperatures are already occurring:
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Adjust gas extraction to prevent oxygen intrusion
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Enhance leachate drainage to remove heat and moisture
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Monitor pressure and temperature in real-time
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Consider excavation only as a last resort
A proactive strategy is cheaper, safer, and more effective than reacting to failure.
Explore the Science
Additional Research
To view Scholars who have worked or are currently working on research projects related to ETLFs, visit our Scholar page.
FAQs
The National Waste & Recycling Association has compiled a list of commonly asked questions and FAQ’s regarding elevated temperature landfills. To view the PDF, click here.