The project of installation of bio-toilets in passenger coaches has not yet been completed. The project is still in progress. More than 49,000 bio-toilets have been installed by Indian Railways in passenger coaches till 31.10.2016.
The additional cost of providing bio-toilets in one coach (4 bio-toilets) is ₹4.0 lakh approximately and for the in-service coaches, which require replacement of structural members for fitment of bio-toilets, the additional cost is approximately ₹ 16.0 lakh per coach.
At present, there are more than 900 trains in which bio-toilets have been introduced either in all coaches or in some coaches of the trains. More and more trains are being progressively augmented with coaches fitted with bio-toilets.
Anaerobic digestion process is applied for the digestion of human excreta in the bio-toilets that are being fitted in passenger coaches of Indian Railways. No human excreta is thrown out on the railway track from a bio-toilet fitted in trains. In these bio-toilets, which are fitted below the coach floor underneath the lavatories, the human waste is collected from toilet and is acted upon by a colony of anaerobic bacteria that convert human waste mainly into water and bio-gases (mainly Methane CH4 & Carbon Dioxide CO2). The gases escape into the atmosphere and wastewater is discharged after disinfection onto the track. Human excreta thus do not fall on the railway tracks.