If you happen to travel in Rewa Express, you will notice a slight change in its coaches: small steel tanks fitted between the wheels. These are part of environment-friendly toilets, where the excreta is treated and stored. Coaches in Rewa Express, running between Delhi and Rewa in Madhya Pradesh, are being equipped with biological treatment facility. Unlike a normal toilet, in the bio-toilet only the water trickles down the track, while the sludge is retained in the tank.

Bio-toilets are part of an experiment to try out different types of eco-friendly toilets in trains. The Indian Railways plans to install eco-friendly toilets in all its 9,000 trains by 2011-13. And it is about time the railways changed tracks from open to