Sun Xiuli tosses vegetable leftovers into a bucket and sprinkles them with enzymes, as one of the participants of a garbage recycling project in Tianjin. Zheng Xin / China Daily

While it's not exactly transforming trash to treasure, retiree Sun Xiuli can turn her rotten vegetables into fresh organic produce through a kitchen waste recycling project in the Tianjin Economic-Technological Development Area (TEDA).

It's simple, she says.

She tosses her kitchen scraps into a bucket and sprinkles them with enzymes. Then a volunteer arrives to swap her composting waste for fresh vegetables.

Her food waste is transformed into organic fertilizer that's used to nourish the vegetables the program provides. Those vegetables' leftovers, in turn, restart the cycle.

"My work is simply putting the food scraps in a bucket and adding the enzymes," she says.

"Then I just wait for the volunteers to bring me fresh vegetables."

Sun's is one of more than 300 households to participate since 2008 in the free-market zone of Tianjin's Tanggu district. And the project is one of many throughout the country.

Coanda Energy Corp founder Feng Shaoqiang says he started the project when he realized China's potentially useful kitchen waste is usually buried in landfills, where it undergoes chemical processes that often cause it to ooze back to the surface as hazardous sludge.

About 70 percent of Chinese garbage is kitchen waste. It accounts for about 61 percent of Beijing's trash, the Beijing Municipal Commission of City Administration and Environment reports.

"We've had to keep the project small because of insufficient funding," Feng says.

"But many of the participants' neighbors have been calling me to ask for enzymes."

However, in this case, demand outstrips supply in Tianjin and beyond, Chen Liwen, a researcher with the NGO Green Beagle, explains.

Feng says the overflow of food waste creates a duality of problems.

"It puts pressure on waste treatment facilities and wastes recyclable resources," he says.

"Why bury what could be useful?"

And especially when what's potentially useful becomes certainly harmful, as the food waste oozes out of landfills as hazardous, even carcinogenic, sludge.

But most households don't think about pollution when they sign up.

"It's garbage for cabbage," Feng says.

"People say, 'Why not?'"

But there are concerns as to whether or not the enzymes can survive cold and wet conditions.

"While it sounds like a great system, we have to consider actualities," Friends of Nature researcher Zhang Boju says.

Zhang says composting enzymes can only live in humid conditions warmer than 18 C. But assuring those conditions in most of northern China, including Tianjin and Beijing, is impossible.

"If the enzymes die, the trash becomes rank and wormy."

Unlike Europeans and Americans, most Chinese don't have a backyard in which to set up a waste disposal area.

Zhang says most of the various food waste-recycling schemes - employing everything from earthworms to enzymes - his NGO has attempted in Beijing have failed because residents weren't willing to deal with the hassle and complexities.

"They have to cut orange peels into small pieces to help enzymes survive in winter and avoid spicy food, because peppers kill earthworms," he says. "It's just too much trouble. The technology is there. But practical considerations get in the way."

Feng has a different take.

He says that after three years of scientific research, he has found the enzymes can survive in temperatures as low as -17 C and in water.

"And there's no stench during decomposition," he says.

The problem Feng faces, he says, is a lack of cash and government support.

"We must rely on volunteers," Feng says.

Another is that most farms in Tianjin refuse to take natural compost because chemical fertilizers are easier to apply.

Feng says his company has run in the red since 2008.

"But we hold steadfast to our beliefs," he says.

"We won't give up."