India’s fuel policy is increasingly being shaped by blending targets. First came ethanol blending mandates. Then E20 became the national standard. E85 is now part of the country’s longer-term fuel strategy. The latest addition could be diesel blended with up to 15 per cent isobutanol. The case for isobutanol is not difficult to understand. It offers several advantages over ethanol, could reduce dependence on imported crude oil, and may help lower emissions from India’s vast diesel fleet.

But before another fuel target becomes policy, it is worth asking a broader question: are fuel transitions being driven by market readiness or by mandates? The government’s interest in isobutanol reflects a practical limitation in India’s current biofuel strategy. While ethanol blending has become a central pillar of petrol policy, extending biofuels to diesel has proved far more difficult. The technical limitations of ethanol-diesel blends led policymakers to consider alternatives better suited to the diesel market, with isobutanol emerging as the leading candidate. Unlike ethanol, isobutanol is inherently more compatible with diesel.

It can be blended with fewer technical constraints for engines and existing fuel infrastructure, making it a more practical option than earlier........

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