isobutanol-diesel blending for 21 September 2025

Isobutanol-Diesel Blending Latest News

• India is exploring isobutanol-diesel blending as an alternative to ethanol, with a pilot project underway to assess its technical and economic feasibility.

Introduction

• India is pushing forward in its biofuel journey, experimenting with new alternatives to conventional fossil fuels to meet its energy and climate goals. 
• After ethanol blending with diesel proved technically unsuitable, the government and the Automotive Research Association of India (ARAI) have turned their attention to isobutanol, an alcohol-based compound with promising blending properties. 
• Transport Minister Nitin Gadkari recently announced that India is working on pilot projects to evaluate the feasibility of isobutanol-diesel blending, which, if successful, could make India the first country to achieve this breakthrough.

Understanding Isobutanol and Its Properties

• Isobutanol is a four-carbon alcohol widely used as a solvent in industries such as paints and chemicals. Its key attributes include:
  • Higher Flash Point: Less volatile and safer than ethanol, lowering fire risks.
  • Better Miscibility with Diesel: Compared with ethanol, isobutanol blends more effectively with diesel without requiring extensive chemical modifications.
  • Versatile Feedstock: Like ethanol, it can be produced from sugarcane syrup, molasses, and grains through microbial fermentation.
• These properties make it technically more compatible with diesel engines than ethanol.

Why Ethanol Blending Failed with Diesel

• Ethanol has been a cornerstone of India’s biofuel policy, especially in petrol blending, where the country has achieved 12% ethanol blending in 2023-24. 
• However, blending ethanol with diesel faced hurdles:
  • Low Flash Point: Increased volatility and fire risk.
  • Poor Compatibility: Required chemical additives to stabilise the blend.
  • Engine Concerns: Blending caused ignition and combustion irregularities in diesel engines.
• Thus, isobutanol emerged as a promising alternative for diesel blending.

Production and Economic Viability of Isobutanol

• Isobutanol production follows a fermentation process similar to ethanol, but with specially engineered microbes that convert natural sugars into isobutanol. 
• According to the Indian Sugar Mills Association (ISMA):
  • A sugar refinery with 150 kilo litres per day (klpd) capacity can produce 125 klpd ethanol and 20 klpd isobutanol with minor infrastructure modifications.
  • The use of surplus sugarcane and molasses, already abundant in India, provides a steady raw material supply.
• However, the imbalance between rising cane prices and stagnant ethanol procurement prices poses an economic challenge that could extend to isobutanol production.

Technical and Performance Challenges

• While isobutanol blends better with diesel than ethanol, experts highlight several technical considerations:
• Cetane Number:
  • Isobutanol has a lower cetane number than diesel, which may reduce combustion efficiency.
  • This could cause engine knock, reduced power, and long-term damage.
• Additives Requirement:
  • Cetane improvers would be needed, increasing costs.
  • Blending beyond 10% isobutanol is not advisable due to performance risks.
• Emission Reduction Potential:
  • If optimised, the blend can reduce harmful emissions and support the import substitution of fossil fuels.

Pilot Project and Global Context

• ARAI has initiated a pilot project, expected to take about 18 months, to study the impact of isobutanol-diesel blending across different vehicle classes. 
• If India succeeds, it will become the first nation to commercialise this blend.
• Globally, biofuel innovation has largely focused on ethanol, biodiesel, and advanced biofuels. 
• India’s foray into isobutanol represents an effort to diversify its biofuel basket while reducing dependence on imported crude oil.

Source: TH