New Delhi, Sept. 26 -- Prime Minister Narendra Modi's recent inauguration of a massive bamboo-based bio-refinery in Assam to produce fuel-grade ethanol is testimony to the government's resolve to diversify feedstock for bio-fuels beyond India's mainstay of maize and sugarcane.

The biofuel initiative has had considerable success. Filling stations today supply petrol with up to 20% ethanol content, aiming to serve three objectives: one, reduce foreign exchange outflows, since we import 88% of our oil needs; two, raise farmer earnings; and three, reduce carbon emissions.

But diversifying inputs is a challenge. To appreciate this, a review of the measures taken to arrive at the current blend is instructive.

Over the last decade, the Centre...