A good place to start with India's problems of poor sanitation (see, for example, (Nature 486, 185; 2012) would be the country's 150-year-old railway network, which carries 30 million passengers every day. Hygienic sanitation technologies have yet to be installed in all passenger coaches.

The basic lavatory design throws excreta on to the open railway tracks. This system risks spreading pathogens and parasites to distant locations.

One solution would be to install small biogas plants on trains or at stations. These would generate revenue — from excreta — that could be used to employ cleaning and disposal squads.