Ethanol-Blended Diesel Fails Safety Test, Government Rules Out Rollout

The government has ruled out ethanol-blended diesel for wider use after tests found the fuel fails required safety specifications. Oil marketing companies found blending ethanol into diesel sharply lowers its flash point, Minister of State for Petroleum & Natural Gas Suresh Gopi told Parliament.

This follows the government's push to expand ethanol blending beyond petrol, where E20 and E85 fuels, containing 20 percent and 85 percent ethanol respectively, are already sold in India.

Image Source:PTI

Public sector oil marketing companies tested ethanol-diesel blends at their research and development centres, working with accredited laboratories and automobile manufacturers. The evaluations found the blend does not meet the mandatory flash point specification for diesel.

Ethanol is a two-carbon alcohol with a polar structure, which resists mixing with diesel's oily consistency. The two fuels separate when stored together unless chemical binders are used, and these binders add significant cost.

Ethanol has a flash point of just 12 to 13 degrees Celsius, against the minimum 35 degrees Celsius diesel requires. This places the two fuels in different petroleum safety classes, complicating storage and transport.

Even with proprietary binders, automakers have stayed cautious about pushing ethanol content in diesel past 5 percent, since combustion issues emerge in the blend beyond that level.

Isobutanol - The Alternative To Ethanol-Blended Diesel

A pilot trial for diesel blended with 2 percent isobutanol is expected to begin in the second quarter of FY2027, Tata Motors Commercial Vehicles managing director and CEO Girish Wagh said last month. A government task force involving automakers, oil marketing companies and testing agencies is leading the initiative. Tata Motors is working with Hindustan Petroleum to source the specialised blended fuel for the tests.

Isobutanol is a four-carbon alcohol with a flash point of 27 to 30 degrees Celsius, keeping it in the same Class B petroleum category as diesel, unlike ethanol-blended diesel. Initial trials found a 10 percent isobutanol blend stayed stable for more than 40 days without separating.

Dynamometer tests using standard Indian driving cycles showed a 5 percent isobutanol blend cut emissions, with only a 1 to 2 percent impact on mileage. Wagh added that isobutanol could reduce dependence on imported fuels, despite its lower calorific value than regular diesel.

Minister of State for Petroleum & Natural Gas Gopi clarified that isobutanol is not currently being blended with diesel, meaning no alcohol-based diesel blending programme is yet in commercial operation. Gopi also said no decision has been taken to raise ethanol blending in petrol beyond the existing 20 percent target.

Any increase would follow further scientific studies and consultations with automakers, oil companies and research institutions. Gopi added that no such decision is currently under consideration. The government is separately examining ethanol as a potential cooking fuel through the LPG Equipment Research Centre, a joint venture of Indian Oil, Hindustan Petroleum and Bharat Petroleum. The initiative could cut India's dependence on imported LPG while creating another outlet for domestic ethanol.