From human waste to 'black gold'

Today, he works with government officials, academics, health planners and universities. As a guest professor at the sustainable environmental sanitation department of the university in Beijing, he spends his time working with students to answer questions around waste that are getting more crucial as cities fill up.

Among other initiatives, he now provides technical assistance for biogas training to municipal governments as part of the US government's Global Methane Initiative. He also consults on economic projects related to biogas in the country.

A central part of his life's work has been looking at how to keep the waste-recycling process hygienic, a top concern of the Chinese government from the beginning. While China is far ahead of other developing countries in terms of urban wastewater collection systems, its treatment rate is not as advanced.

"So the user doesn't come into direct contact when expelling their excrement," Mang said. "But where does it go after? From that sense, we will need to find safer pathways of disposal and reuse."

'Poo power'

The catch-up of waste treatment from low penetration rates in China is driving "a waste revolution," with key treatment operators likely to grow 200 to 400 percent in volume in the next five years, Credit Suisse said in an Oct 6 note on China's environment sector. The analysts didn't specifically mention the toilet-waste industry. Only part of Beijing's waste is converted into resources. Other portions are routed to treatment plants or dumped in water or landfills.

Toilet lights

New migrants to cities are one challenge to mass implementation of China's policies, with many still seeing the toilet as a trash can and dumping everything from batteries to newspapers in the bowl.

Also, because Chinese often cook with fresh ingredients, the overall mix of waste tends to be wetter than in Europe, Mang said. "It's very humid so it needs too much energy to incinerate, that's why you can't copy the European model," he says with a hearty chuckle.

Then there is the challenge of missed opportunities. For that, Mang is advocating for better maintenance of light bulbs in public toilets.

"People have to go at all hours of the night - if you don't give them light, how can they see where they're going?" he says, referring to excrement that sometimes piles up in the mornings in public restrooms. "That's a lot of wasted waste."