Monday, May 20, 2013

Restaurant Waste is Pig Feed

China has millions of restaurants and cafeterias that generate an estimated 60 million metric tons of food waste annually. A large, but unknown, portion of this waste is used to feed pigs. There are many online articles about swill-feeding of pigs and crackdown efforts. Local authorities concerned about spoilage and the potential to spread disease, have been trying to stamp out this swill-feeding activity. A renewed effort is underway, apparently motivated by the connection of "gutter oil" as a by-product of cooking down the restaurant waste.

A reporter visited a village outside Changsha in Hunan Province where large boiling vats filled with food waste gave off a pungent odor. After cooking, the swill will be fed to hogs. The oil forms a thin layer on the top of the vat and is siphoned off and placed in metal drums to be sold as "gutter oil." The director of the local food and drug bureau calls these swill farms a "headache" and claims they are hard to find (although the reporter managed to find five of them to visit).
A swill-feeding operation

Restaurants and cafeterias frequently sell their waste to dealers who transport it in small vans and carts to small and medium-scale hog farms. In most cities this is illegal, but the trade is profitable, and authorities have a hard time stamping out the activity. Restaurants get paid several hundred yuan every few months for the waste and hog farmers can use swill to feed their pigs at half the cost of commercial pig feed.

In 2011, a reporter in Changzhou, Jiangsu Province, was alerted by villagers who complained about a neighbor who fed restaurant waste to pigs. The neighbor had come from another province, rented a plot of land and burned trash to cook down swill and separate out "gutter oil." The reporter saw 7 or 8 pigs in a bamboo shed with uneaten swill on the ground. Other villagers said the farm had been started in 2007 and during the hot summer months they could smell it 500 meters away.
A cart delivers barrels of restaurant waste to a pig farmer near Changzhou in 2011.

This is not a new problem. A 2006 Bejing Evening News article estimated there were at least 20 swill-feeding pig farms on the outskirts of Beijing, most of them operated by migrants from Sichuan Province. One man the reporter interviewed said they can't feed swill to young pigs because they get sick easily, but hogs over 50 kg can eat it with no problem. A lady with a Sichuan accent said it costs 7 yuan per day to feed pigs with commercial feed, but just 2 yuan for swill. The lady said she gets the waste from a restaurant owner she has known a long time--he keeps it a secret and doesn't ask questions about what they do with the waste.

In 2000, Shanghai agriculture authorities carried out a remediation campaign to stop swill-feeding. According to a survey conducted at that time, Shanghai produced 1100 metric tons (mt) of food waste daily, including 780 mt from food and beverage establishments (69%); 130 mt from school cafeterias  (12%); and 220 mt from workplace cafeterias (19%). That's about 400,000 mt annually. A demonstration project set up small treatment facilities and there was a plan to set up a market for recycling food waste. According a 2010 estimate by academics in Qingdao, 500 metric tons of food waste were produced daily in that city and 90 percent was purchased by underground dealers. The oil was extracted, recycled and resold while the residue was fed to pigs.
Pig hungry for swill in Suzhou.

Shanghai is conducting another pig-swill remediation campaign that began in January 2013 and runs through November. The campaign is being conducted in every town and involves agricultural, food and drug, health authorities and police. Agricultural authorities will find farms feeding restaurant waste to pigs, trace their sources, stop illegal behavior and assess penalties. Food and drug authorities will canvas restaurants and cafeterias, check their food disposal records and make sure their waste is collected by enterprises approved by the city. The campaign's goal is for 80 percent of restaurant waste to be recycled in a sanitary way by the end of the year.


On Shanghai's Chongming Island, an enforcement team of 25 people rode around in 11 vehicles to investigate 62 farms feeding food waste to pigs. They handed out copies of a notice forbidding the feeding of restaurant waste to pigs and made the farmers sign an agreement to cease and desist. Local officials plan to form enforcement teams including police and representatives from other government departments to monitor slop-feeding.


Feeding waste to pigs was long the norm in China (and many other places) when nothing was wasted. There is still a strong inclination to utilize waste and there are still a lot of people willing to do this nasty work as long as there is some money to be made. Chinese authorities have plans to treat and recycle the waste or turn it into biogas and fertilizer, but it's easier and more profitable to feed it to pigs.

There is no way of measuring the amount of pork produced from swill-feeding, but let's do some very rough back-of-the-envelope calculations. Start with the 60 million metric tons of food waste estimate. If we assume 30 percent (9 mmt) of that waste is used for feeding hogs and we assume it takes 500 kg of waste to produce a 100-kg hog, that would mean 1.8 mmt of pork produced by the swill farms. If all 60-mmt of waste was used to feed hogs, the number would go up to 12 mmt. By comparison, official statistics say China produced 53 mmt of pork in 2012 (did they count the swill-feeding farmers?).

IF officials are successful at stamping out the swill-feeding, that pork would need to be replaced by grain-fed pigs. With a feed conversion ratio of 3:1, that would imply a need for 4 to 36 mmt of additional commercial feed to replace the swill.

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