NEW DELHI — There's a celebration taking place in the small town of Marora, in the northern state of Haryana. Dozens of school girls sing. Boys shout out slogans. And at the center of it all is a huge squat toilet brought here by India's Toilet Man himself, Dr. Bindeshwar Pathak.

Measuring six-by-three meters, the massive toilet is far too big for use by any human. But it does have a purpose: It's an educational tool, a difficult-to-ignore reminder of how important it is to use toilets. That's the message that Dr. Pathak, a sociologist and founder of the NGO Sulabh International, is working hard to spread in India, where according to a recent national census, one in every two people defecates in the open.

"We have constructed 1.5 million toilets in households, in both urban and rural areas," he says. "And in public spaces we have built about 9,000 toilets."

Simply put, toilets save lives, because without them, human waste is left in the open, spreading killer diseases like diarrhea and cholera, Dr. Pathak explains. They're also a priority for Indian women, offering them safety and dignity, which they lack when forced to defecate in the open, he adds.

Dr. Pathak, or Toilet Man, as he's commonly known, says decades of hard work is now making an impact, especially now that the national government, as of 2014, has committed to a "Clean India" campaign. "We have cleaned up this country," he says. "We have helped. Now the prime minister of India has this program to stop defecation in the open by 2019. Using our technology, the government has built about 70 million toilets."

Dr. Pathak's technology is what's called a "two pit pour-flush" toilet. They are ecologically sustainable, composting devices that don't even need to be cleaned. "One pit is used at a time and the other is kept stand by," he explains. "If the first one is full, we switch over to another one."

After time, the material collected in the first pit can be used for manure or fertilizer, or even used to generate energy. "The human excreta goes to a biogas digester and that is used for burning lamps or cooking food," Dr. Pathak explains. "That way it's fully recycled. We don't allow methane to go to the atmosphere, we burn it. So it helps to reduce global warming and thus prevent climate change."

Dr. Pathak is determined to share his knowledge of toilets far and wide. And he's set up a very unique place to do just that: a toilet museum, in the capital New Delhi. The museum traces the 4,500-year history of the toilet, and features exhibits from 50 countries.

"In 2014, Time magazine carried out a global survey to list the world's 10 weirdest museums. And this museum came in third," Dr. Bagheshwar Jha, the toilet museum's head curator, tells me.

The giant squat toilet in the village of Marora will eventually be displayed here, along with all kinds of replicas. Assistant curator Shikha Sharma points out her favorite one: the throne toilet, once the property of the French emperor Louis XIV. "The king had a constipation problem," Sharma explains. "He used to sit right here."

The toilet museum draws thousands of visitors every year. One of the museum goers, Raju Singh, 28, shows me his personal highlight. "It's a hilarious letter written in broken English to the colonial railway authorities," he explains. "The writer was traveling by a train, and had a strong urge to defecate but there was no toilet. His letter compelled the British authorities to put toilets on Indian trains."

India's Toilet Man has picked up where the colonial-era train passenger left off. Except rather than furnish trains, he wants to put a toilet in every single Indian home.