Bindeshwar Pathak, the sanitation charity founder, is most at home when surrounded by soap dispensers and latrines. He vows to build clean toilets in every impoverished home in India.
Affectionately known as India's "toilet guru", 71-year-old Pathak has spent four decades working to improve sanitation in a country where half of the population relieve themselves in the open air.
Inspired by Mahatma Gandhi, a champion of cleanliness, Pathak has more recently been spurred on by new Prime Minister Narendra Modi who wants to make India free of open defecation by 2019.
"India has the technology and the methodology. What we lack is infrastructure," Pathak said of Modi's vision, as he took AFP on a tour of cheap, eco-friendly toilets that his New Delhi-based charity has developed.
"We also need funds to the tune of $42.3 billion considering each toilet will cost about $320," he said, making quick calculations on a piece of paper.
"We can't claim to be the next superpower when we don't even have something as basic as a toilet for everyone," he said ahead of Thursday's national holiday to celebrate the birthday of India's independence hero Gandhi.
- National hygiene drive -
Modi is due to launch a national cleanliness drive on Thursday, after pledging in August to ensure all households have toilets in the next five years.
From top ministers to lowly officials, all are expected to turn up to work on Thursday to clean up their government buildings -- including their toilets -- many of which stink of stale urine and are littered with rubbish and spit.
"This mission ... aspires to realize Gandhiji's dream of a clean India," Modi said recently after pledging during the May election campaign to build "toilets first, temples later".
"Together we can make a big difference," the Hindu nationalist said.
UNICEF estimates that almost 594 million -- or nearly 50 percent of India's population -- defecate in the open, with the situation acute in dirt-poor rural areas.
Some 300 million women and girls are forced to squat outside normally under the cover of darkness, exposed not only to the risks of disease and bacterial infection, but also harassment and assault by men.
The issue was thrown into the spotlight in late May when two girls, aged 12 and 14, were allegedly attacked as they went into the fields to relieve themselves. Police are investigating if they were gang-raped before being lynched.
- Two-pit toilet technology -
Pathak, the founder of sanitation charity Sulabh International, has already constructed 1.3 million toilets for households using his cheap, two-pit technology.
When one pit is filled, it is covered, and the other pit is used. Within two years, the waste in the covered pit dries up, ridding itself of pathogens and ready for use as fertilizer.
Such toilets use less than a gallon of water per flush compared to 2.6 gallons (10 litres) for conventional latrines and do not require attachment to underground sewer lines, which are nonexistent in most villages.
Pit toilets also eliminate the need for the degrading task of manually removing toilet waste by workers who are seen as the "ultimate untouchables" in caste-ridden India.
Pathak is determined to banish the need for such "manual scavengers", who often scoop out excrement with their hands into wicker baskets, a campaign also pushed by Gandhi before his death in 1948.
Himself an upper-class Brahmin, Pathak recounted how he was made to consume cow dung and urine as part of a "purification ritual" after he touched a woman, who used to clean latrines, as a 10-year-old boy.
"This moment has stayed with me," he said.
Pathak's charity has also harnessed "bio-gas' produced from human waste which is used to generate electricity to power the charity's offices. The gas has also been bottled for use as fuel for cooking.
Despite his achievements, Pathak said his task is far from complete, and he was determined to change cultural and social attitudes against toilets. Many people in India consider toilets unhygienic and prefer to squat in the open, believing it is more sanitary to leave waste far from your home.
"Many people (also) find toilets stifling," said Pathak. "We tell them that you can keep the top of the toilet uncovered if you want to have a feel of defecating in the open."