The other day I was reading about the Virgin Atlantic 747 jumbo jet that flew last week from London to Amsterdam on biofuel. It's quite a record - Virgin is now the first airline in the world to fly on renewable fuel.

Around the same time, Balu, a manic biker friend who spends his days tooling around with bikes, called to say he's developed a motorcycle that runs on vegetable oil. "Just bung some refined oil from your kitchen into the bike," he said, "and zip off�isn't that amazing?" Amazing it was, I agreed, even in a time when everyone seems quite obsessed with bio-fuels.

I begged Balu to take me for a spin. "I call it my Veggie Bike," he roared over the growl of the bike and grumble of the traffic. When I asked him what gave him the idea of modifying the bike to run on cooking oil, his answer was simple: "substituting vegetable oil for diesel or petrol makes its emissions much cleaner, and also gives the satisfaction that its carbon footprint is not as large!"

I learnt that the concept of using Straight Vegetable Oil in engines was an old one - when Rudolf Diesel invented the first diesel engine about a hundred years ago, he made it run on groundnut oil.

As we were driving back after meeting Balu and his Veggie Bike, I told my driver what I had just seen. "So what is the advantage if using SVO or bio-diesel instead of good old petrol or diesel?" he asked. I explained how they were non-renewable fuels, while vegetable oil came from an easily renewed source.

"That is why they're so amazing," I said with my new found zeal, "they can be used to run existing means of transport without burdening our air with added carbon dioxide!" In fact, I went on, unlike fossil fuels like coal and petrol, bio-fuels are considered to be carbon-neutral, which basically means that they remove carbon dioxide from the atmosphere, and exude the same amount when burnt.

"Did you know," I went on, "bio-diesel is now being used extensively in the US? Most of its federal, state and transit fleets use bio diesel neat, or mixed with conventional diesel�"

We drove in silence for a while. Then my driver spoke up, "Madam, even today in our village, people walk for miles and miles everyday. Bullock carts carry fodder, harvested vegetables and people from one place to another. The younger boys zip around, but only on bicycles. When we go to the nearest town - villagers think it is large although it is very small by metro standards - we go to the market in rickshaws."

My mind full of the Veggie Bike, bio-fuels and bio-diesel, I didn't quite get his drift till he spelt it out for me. "In Indian villages, the concepts of bio-fuels and carbon footprints do not exist. Yet, people use cycles, bullock carts, rickshaws and their own two feet, none of which cost the environment anything," he said.

In cities, by contrast, people don't walk or cycle, except to exercise. And to do that, they drive to gyms in petrol-thirsty cars to walk on treadmills that guzzle electricity. How complicated and strange things were from this new perspective!

So did he think, then, that this craze for bio-fuels was an urban thing, I asked. "Not really. The way I see it, it's more about who can afford what," he said, adding kindly, "but it's still quite a nice thing for people like you to be so enthusiastic about."