Fumigation is an emission reduction technique where a secondary fuel (usually LPG, CNG, or alcohol) is introduced into the engine’s intake air stream alongside the primary fuel (diesel or gasoline). This method helps reduce smoke (PM), NOx, and CO emissions by improving combustion efficiency.
1. How Fumigation Works
Secondary fuel (e.g., LPG, ethanol, or hydrogen) is vaporized and mixed with intake air.
The air-fuel mixture becomes leaner and burns more completely, reducing soot formation.
Lower combustion temperatures help reduce NOx emissions.
Types of Fumigation Systems
| Type | Fuel Used | Best For |
|---|---|---|
| Diesel-LPG Fumigation | LPG (Propane/Butane) | Heavy-duty diesel engines |
| Diesel-Ethanol Fumigation | Ethanol/Methanol | Older diesel engines |
| Gasoline-CNG Fumigation | Compressed Natural Gas (CNG) | Petrol engines in dual-fuel setups |
| Hydrogen Fumigation | Hydrogen gas (H₂) | Experimental/low-emission projects |
2. Benefits of Fumigation
✔ Reduces smoke (PM) by up to 50% in diesel engines.
✔ Lowers NOx emissions (due to cooler combustion).
✔ Improves fuel efficiency (better combustion = less waste).
✔ Works with existing engines (no major modifications needed).
✔ Can use alternative fuels (LPG, ethanol, hydrogen).
3. Challenges & Limitations
⚠ Requires extra fuel storage (LPG/CNG tanks or alcohol injection).
⚠ Potential engine knocking if not properly tuned.
⚠ Safety concerns (flammable gases require proper handling).
⚠ Not a complete solution – best combined with other emission controls (EGR, SCR).
4. Fumigation vs. Other Emission Control Methods
| Method | How It Works | Best For |
|---|---|---|
| Fumigation | Adds secondary fuel to intake | Diesel smoke reduction |
| EGR | Recirculates exhaust gas | NOx reduction |
| SCR (AdBlue/DEF) | Uses urea to break down NOx | Modern diesel trucks |
| DPF | Traps and burns soot | PM control in diesels |
5. Applications of Fumigation
Old diesel trucks & buses (to meet emission norms).
Marine & industrial engines (where retrofitting SCR is expensive).
Agricultural machinery (reducing smoke in tractors).
Racing & performance tuning (methanol/ethanol fumigation for power gains).
Conclusion
Fumigation is an effective, low-cost method to reduce emissions in diesel and gasoline engines, especially where aftertreatment systems (like SCR or DPF) are not feasible. However, proper calibration and safety measures are crucial for optimal performance
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