In a city where every other taxi driver demands Rs 20 or 30 more than the metered fare, the only "extra" Dhananjay Chakraborty demands of his passengers is to plant a sapling each.

Dhananjay's is a green taxi in every sense, and his crusade one of a kind.

The 40-year-old drives an Ambassador with a bed of real grass on its roof, eight potted plants placed on the tray behind the rear seat and a green interior to go with his message to save the environment and take care of trees.

"I have loved trees from childhood and participate regularly in plantation programmes of various organisations. I have noticed that trees are planted but nobody takes care of them and soon they wither away and die. So I have decided to spread the message that trees must be planted and cared for. Wherever I travel in the city, I ask my passengers to do so," he told Metro.

Dhananjay, Bapi to his family members, has earned the nickname Gechho Bapi for his love of trees. Such is his passion for the green cause that he has spent more than Rs 22,000, equivalent to what he earns after toiling for a month and a half, on creating the bed of grass on the roof of his taxi.

The vehicle, which he has named Sabuj Rath (green chariot), has been grabbing eyeballs since Dhananjay unveiled its new look a couple of weeks ago.

"The tray weighs around 65kg. But I have distributed the weight equally across the green bed to ensure that the car roof isn't damaged. One of the benefits is that the grass cools the interior and I take pride in the fact that my taxi is a lot cooler than any other non-AC car," said Dhananjay, who has been driving taxis for 14 years.

The idea of the green roof came from a photograph of a taxi with a similar look that a friend of Dhananjay's had found on the Web. "He suggested that I try it, which I did," smiled the proud driver of Calcutta's first taxi with a terrace lawn.

The base of the green bed is made of metal. Dhananjay spread a layer of soil, white sand, stone chips and netting over the tray before planting the grass. To drain out excess water, there are tiny holes at the base of the tray.

"The extra weight has increased the fuel consumption of my taxi but I don't mind it," he said.

While he has always been close to nature, Dhananjay found his green calling more than a decade after he started driving a taxi. "Three years ago, I found an empty liquor bottle with a lovely shape in the back seat of my taxi at night. I put a money plant in the bottle and fixed it on the tray behind the rear seat. The plant survived and, within a few weeks, it was touching the edges of the rear window. Many passengers liked it. That's when I decided to plant more trees and ask others to do the same," recounted Dhananjay.

His fellow taxi drivers ridiculed him; some thought he had lost his mind. Today, most of them are supportive of his initiative.

Dhananjay doesn't own the taxi that has become the vehicle of his crusade - he was forced to sell his own taxi eight years ago to arrange funds for his treatment following an accident - but that isn't a hindrance. Amrish Singh, who owns the car, has known Dhananjay for a long time and respects his passion for the green cause.

"He is one of the safest drivers you can find and also maintains the vehicle better than most. When I first asked him to drive my car, he told me that he would decorate it with plants. I agreed and am happy to be a part of the cause," said Amrish, who owns five more taxis and drives one of them himself.

Dhananjay hasn't stopped at turning his taxi into a green zone. He carries a sheaf of leaflets to give to passengers and anyone curious enough to strike up a conversation with him.

The leaflets contain small poems and sketches by Dhananjay, all of them about the environment. The design for the leaflets are by a passenger who went on to become his friend.

Dhananjay has also decorated the taxi stand at Tollygunge Karunamoyee with flowerpots and regularly distributes seeds and saplings among passengers and passers-by who show interest.

He has a Facebook account called Bapi Green Taxi and his email ID is bapigreentaxi@gmail.com, where passengers and well-wishers can write in with their suggestions.

"He seems to be a crazy person but maybe our society needs more crazy people like him," environment activist Bonani Kakkar said when Metro told her about Dhananjay and his green taxi.

She was instantly reminded of a man who travels from Mumbai to Pune by train, throwing seeds out of the window along the way. "Some of those germinate and become trees. But I didn't know there is a person in our city who is doing something novel to save the environment. I think we should all learn from him and join his cause," Kakkar said.