Is it feasible to blend isobutanol and diesel?
Context
- On September 11, Union Transport Minister Nitin Gadkari announced that the Automotive Research Association of India (ARAI) is piloting the blending of isobutanol with diesel.
- This comes after unsuccessful attempts to blend ethanol with diesel, despite ethanol being available in surplus.
What is Isobutanol?
- An alcoholic organic compound, used as a solvent in industries like paints and coatings.
- Has flammable properties and is now being explored as a biofuel alternative.
Why Ethanol Was Discarded for Diesel Blending
- Low flash point: Higher risk of fire due to volatility.
- Poor miscibility with diesel.
- Engine compatibility issues.
- Surplus ethanol is better suited for blending with petrol (E10, E20).
- Economically unviable: Procurement price issues and declining incentives for sugar mills.
Why Isobutanol is Being Considered
- Better miscibility with diesel compared to ethanol.
- Higher flash point → Safer to handle and store.
- No need for blending enhancers/additives for miscibility.
- Can be produced from the same feedstock as ethanol (sugarcane, molasses, grains).
- Helps utilise surplus sugar and supports energy security.
- Potential for reduced emissions and import substitution.
How is Isobutanol Produced?
- Feedstocks: Sugarcane syrup, B-heavy molasses, grains.
- Production process:
- Engineered microbes (not conventional yeast) ferment natural sugars into isobutanol.
- Requires retrofitting of existing ethanol plants: Fermentation + distillation tanks.
- Example: A plant producing 150 KLPD of ethanol can divert ~20 KLPD to isobutanol with minor changes.
Pros of Using Isobutanol as a Biofuel
✅ Higher flash point than ethanol → safer for diesel blending.
✅ Better miscibility with diesel.
✅ Leverages existing biofuel infrastructure (molasses, cane juice, etc.).
✅ Can support farmers & sugar industry by using excess sugarcane.
✅ Potential to reduce diesel imports and lower emissions.
✅ Aligns with Net Zero target (2070).
Challenges / Concerns
Low cetane number:
- Leads to poor combustion quality.
- Can cause diesel knock, engine damage, and power loss.
- May require cetane improver additives → increases cost.
Miscibility concerns:
- May need to add biodiesel to ensure uniform blending.
Economic Viability:
- Retrofitting costs, lack of commercial scale testing.
- Ethanol price imbalance → discouraging ethanol/isobutanol production.
Limited blending percentage:
- Experts recommend not more than 10% isobutanol in diesel to avoid engine issues.
Status of the Pilot Project
- Being carried out by ARAI.
- Pilot project will take around 18 months to complete.
- If successful, India will become the first country to blend isobutanol with diesel.
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