While you often hear Chinese parents tell their kids to not waste food, the fact is food waste accounts for about 70 percent of the country's mounting garbage production. That's compared to less than 20 percent in many developed countries, where sorting and processing have been the norm since the 1980s. And as China's waste processing capabilities simply can't keep pace with the amount of garbage that is being produced, food waste is a bigger problem than it might be. "As people's lives improve, the catering industry is booming and dietary habits are changing, so we're producing massive amounts of food waste," Beijing Technology and Business University's Department of Environmental Science and Engineering professor Ren Lianhai says.

"China has a long way to go in terms of better disposal because it lacks a national policy, scientific management and processing methods."

Beijing was among a slew of local governments to pass regulations in 2011 about trash sorting and food waste disposal, largely because of public concerns about "gutter oil" - cooking oil retrieved from drains and sometimes reused by restaurants.

The problem is that governments, NGOs and enterprises are struggling to cook up solutions for kitchen waste disposal and are finding they don't work or are difficult to implement.

Recipes that are being tried include composting the waste into organic fertilizer using enzymes and earthworms, burning it to create electricity, feeding it to pigs and even using gutter oil as biofuel to power Dutch Airlines' planes.

"Kitchen waste has become a primary pollution source and imposes serious risks to people's health and the environment," Ren says.

Ren, who has studied waste management for more than a decade, explains the dangers of burying kitchen waste in landfills.

China's food waste is 74 percent water - that's three times the saturation of US and European kitchen waste. It's referred to as "wet waste" globally.

The pressure of being buried, combined with the chemical reactions of microbial biodegradation, causes the water to ferment and percolate, forcing hazardous and even carcinogenic sludge to ooze out, Ren explains.

And food waste poses sanitation hazards before it even reaches the landfills, he adds.

Take Beijing, for example. The capital's households produce 11,000 tons of kitchen waste, plus the 2,500 tons that spew out of restaurants, a day. But the municipality's three large-scale processing plants can only handle 800 tons a day of food waste.

The most common methods of kitchen waste disposal are feeding it to pigs and composting.

While the evidence is inconclusive, many experts worry that turning household kitchen waste into pig slop is dangerous.

Pork is China's most popular meat and its presence in hog feed creates the risk of homology. Homology is cannibalism among animals that typically don't eat the meat of their own species in nature and can cause prion infections, such as mad cow disease.

The Ministry of Agriculture has created a panel to study the risks but hasn't reached a consensus.

Although the practice is common in Japan and South Korea, some of China's local governments, such as Fujian province's Xiamen city, have outlawed it.

Organic composting, though promising, also faces challenges.

Many pilot projects have problems, such as people not sorting their trash, or collectors dumping sorted trash together or waiting too long to pick it up, creating a stench.

"Trash processing is a chain," Beijing Municipal Commission of City Administration and Environment garbage disposal official Chen Ling says.

"We can't expect people to sort out kitchen waste if there's no channel to handle it."

Ren says the chain's weak links come from a diffusion of responsibility.

"The dilemma is that experts complain about management, while officials complain about technological deficiencies," he says.

There are also chemical reasons it's difficult to compost in China.

"Chinese food contains too much oil, especially animal tallow, which coats the waste in a thick cover that seals out oxygen microbes need to biodegrade the waste," Ren explains.

One solution is to dilute the food waste with other biodegradable trash, such as paper.

Insufficient storage is another problem. Farming is seasonal, but food waste is produced year-round.

And even if there were more storage facilities, compost rots too quickly to last from harvest until the next planting.

In addition, the saltiness of Chinese food means the fertilizer it becomes can make arable land fallow over time, Ren says.

Still, several projects are running that turn kitchen waste into organic fertilizer around the country.

Many NGOs, such as the Fujian Environmental Protection Volunteer Association, exchange organic vegetables for correctly sorted trash.

The produce is grown with the organic fertilizer from their community's waste, meaning that, theoretically, the melon rind a household throws out can end up back on the family's table as a fresh organic melon.

The association's founder Zheng Dijian believes it's all about incentives.

"If people get something out of sorting their garbage, they will," he says. "If they don't, they won't."

Another kitchen waste use idea being tried out is incineration to create electricity.

Trash in Chaoyang district's Chaoyang Circular Economy Industrial Zone, in Beijing, is compressed to wring out the water, left to dry for five days and then incinerated at the 200-hectare solid waste incineration plant.

About 1,600 tons feed the furnaces a day, creating 220 million kilowatt hours - equivalent to 70,000 tons of coal - annually. About 70 percent of that electricity powers the industrial zone while the rest flows into the North China Power System.

But it's uncertain how - and if - this could work on a nationwide scale.

Ren, who works on a national panel devoted to developing the country's kitchen waste disposal system, says Beijing's government plans to build at least one large wet waste processing plant in every district and county.

The problem is that nobody's sure what sort of plant they should construct.

The same quandary faces the proposed 100-150 plants to be built nationwide before 2016. They should be able to process a total of up to 30 million tons a year.

"I'm glad to see people are working on this," Ren says.

"But we still have a long way to go."

Erik Nilsson contributed to the story.

Going from garbage to cabbage and back again

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."

Half-baked or overdone?

Despite the winter chill, retired teacher Tian Liping sticks to her daily routine of standing by the trash cans in her community to check the garbage that is being dumped.

"Some people don't do wet and dry separation. They just throw it all in and rush to work," says Tian, who wears a down jacket to keep out the cold and rubber gloves so she can check the trash.

From 7:30-9 am and 6:30-8 pm, the 63-year-old picks out recyclables along with 10 assistants in the Zaoying Beili community of Beijing's Chaoyang district.

The community - one of the capital's 1,800 garbage management pilot communities in 2010 - has three trash canisters in different colors for kitchen, recyclable and other waste.

The idea is to reduce waste at the source.

When Tian is off duty, a disposal worker rides a tricycle around the community and empties the canisters of recyclable waste.

The community's manager Song Shuangming has also hired environmental and sanitation workers from a recycling company to guarantee the separation initiative works properly.

The waste is later transported by Beijing Environmental Sanitation Administrative Bureau (BESAB) trucks to a transfer station and is compressed.

Here, one garbage compressor deals with kitchen waste, while two others deal with the rest of the garbage.

The compressors, which have a 5-ton loading capacity, have a sliding track onto which the garbage is transported into a container and squeezed, causing slop to flow out of a pipe.

Water is sprayed on the trash during the summer heat to dilute the stench .

The equipment can also weigh the garbage and even show where it comes from through Radio Frequency Identification (RFID), a wireless automatic-recognition technology.

The kitchen leftovers can be turned into useful materials at the kitchen waste treatment plant, BESAB director Liu Jindong says.

Sprayed with probiotics, the slop stirred in a 4-meter-high fermentor for about 10 hours becomes a kind of meat floss. It then goes to a feed processing plant, where it is made into fine organic feed and microbial inoculum.

These are used on gardens around the capital to cultivate strawberries, peaches and apples.

A study by the Beijing Municipal Commission of City Administration and Environment has determined the daily production of municipal waste in the capital for 2011 decreased to 17,400 tons, 900 tons fewer than 2010.

It's not all good news, however.

Zhonghai Fenglian is running a pilot program sorting trash in Beijing's Haidian district, but resident Hou Qixiao complains the new plastic trash bins handed out by the local authorities are not suitable.

"We can't wait to dump the food waste when the green 10-liter bins are filled up, because it gets so smelly," Hou says. "But the constant dumping of half-full bags of waste means plastic pollution."

Although residents carefully divide domestic garbage into recyclables, kitchen waste and other waste, a collection truck mixes the waste and just dumps it at a nearby site.

No one complained about this until 10 months ago when food waste collections were reduced from once a day to twice a week.

As a result, community residents have to put up with smelly leftovers overflowing from the bins and decomposing in a smelly mess.

"It's worse on hot days and freezes in the winter," says Cheng Mouhong, a property manager in the community. "Residents say they are embarrassed when relatives visit because of the garbage."

Cheng claims there are just three food-waste recycling trucks serving Haidian's 400 pilot communities.

He says the communities in northwest Beijing are overlooked, and the production of waste exceeds the disposal and treatment of it.

Xue Wenjuan, a housewife in the community, loves online shopping, but says there was nothing she could do about disposing of cardboard packaging until the NGO Friends of Nature (FON) launched a green recycling day initiative in early 2011.

Zhang Boju, director of FON, first tried compostable and recyclable separation.

"But most residents were reluctant to comply, because the wet waste is so gooey and dirty," he says.

So the organization finally decided to accede to an idea promoted by the community to separate recyclable waste from the rest, rather than deal with wet waste.

Volunteers from FON go to the community once every two weeks to collect recyclable waste and give out a card, called the "green account", to residents coming for waste disposal.

"The more recyclable waste people dispose of, the more points are recorded on the card," says Lin Youzhu, a college student who has been working as a volunteer collector for seven months.

Residents can exchange the points into gifts from FON.

"More than 300 households applied for the account," Zhang says. "I hope the government pays more attention to initiatives like this and improves its garbage management."

What goes in must come out

It is New Year's Eve and a buffet restaurant in Beijing's China World Hotel is bustling.

Li Mengzhong, the hotel's assistant chief engineer, is busily inspecting the kitchen. One of his major duties is garbage disposal.

"It's very complicated work," Li says. "We have to put the mess in order."

The hotel has three restaurants, a bar, two lounges and a staff cafeteria that holds nearly 2,000 people a day. The hotel creates more than 5 tons of kitchen waste every day.

Li points to a workbench in the kitchen where employees separate waste from the dinner tables into several categories.

"We sort bottles, paper, chopsticks and other recyclables out of the food waste," Li explains.

Various types of garbage are put into different colored cabins. The food waste goes into a black bin and is put underground cold storage.

Chaoyang district's government sends a garbage truck to collect the hotel's kitchen waste at about 4 pm every day.

China World has also invested in dehydrators to dispose of food waste before the trucks arrive.

However, not all restaurants dispose of waste in the same way.

Zhao Bin runs a restaurant in Beijing's Liangmaqiao area, which can hold about 50 people. As the government-operated kitchen waste collection hasn't extended to small restaurants, he has to deal with it in other ways.

"The government requires us to separate kitchen waste," Zhao says. "However, I really don't know how to handle it all by myself."

Consequently, Zhao uses private collectors. A minibus will come to his restaurant every day at 10 pm to take the waste away, charging just 10 yuan ($1.50).

"These collectors come from nearby provinces. I don't know exactly how they process the waste."

The Beijing Municipal People's Congress passed a bill in November 2011 to better manage the capital's garbage disposal. Confronted with the public's rising concerns about "gutter oil", the bill emphasized the construction of kitchen waste disposal facilities and regulation of kitchen waste collection.

Chen Ling, an official in charge of garbage disposal at the Beijing Municipal Commission of City Administration and Environment, says the municipal government will promote the use of kitchen waste disposal machines among restaurants and offer technical guidance.

"It's very urgent, and we expect all kitchen waste in Beijing will be correctly disposed of soon," she says.

"It's essential to erase waste at its source. We'll encourage people to be more conscious about waste and avoid producing unnecessary garbage."

According to the new bill, which will come into effect in March, the more waste created, the more money will be charged.

"The simplest way is to avoid ordering too much food," Li says. "Chinese people like luxury banquets, but maybe it is not a good habit. Our waiters will kindly remind the customers when what they have ordered is enough. It saves money on both sides."