Gutter oil: out of the sewer and into the frying pan

Imagine there’s a 1 in 10 chance that your dinner is cooked in oil skimmed from the gutter or even the sewer. Still hungry?

Restaurant patrons in China face these stomach-turning odds, thanks to the illegal trade in ‘gutter oil’ - used cooking oil that’s dredged from gutters and sewers, reprocessed and sold back to restaurants to be used as cooking oil again. Called “distilled sewage” by one commentator, the oil can also contain oil refined from animal offal and deep-frying oil that’s past its prime.

If the source of this oil isn’t enough to quash your appetite, there’s more. Far from a green approach to dealing with kitchen waste, gutter oil - or “digouyou” - is treated with chemicals to clarify it and deal with the odours that inevitably accompany a product with such shady origins.

It begins life as a chunky, putrid stew and is ‘purified’ with calcium bicarbonate and neutralised with alkali to the point that it looks the same as good-quality oil. Chemical dyes and bleaches are other appetising additives used to disguise its origins. Most alarming, though, is the presence of the carcinogen PAH and aflatoxin, a highly carcinogenic mycotoxin.

Not only that, but the animal and vegetable fat in gutter oil can undergo rancidity, oxidation and decomposition, as well as producing toxic substances like arsenic, according to Zeng Jing, a nutrition expert.

Despite the Chinese authorities running a campaign to crack down on gutter oil production, they admit they have no way of distinguishing legitimate cooking oil from gutter oil. Unless companies are caught in the act, there’s no way of determining whether a restaurant is using new or used oil.

Gutter oil production is clearly big business in China: a 2011 crackdown on gutter oil production saw police deal with 128 cases and 60,000 tonnes of gutter oil over a period of four months. It’s frequently referred to as an “open secret” in the restaurant industry in China.

And it’s no wonder, when profit margins are so high. According to Xinhua, the official government press agency in China, raw gutter oil can be purchased for around 6000 yuan a tonne and sold for 8000 yuan a tonne after processing - nearly a third higher than the original price. Another expert, He Dongping, said, “The profit margin is almost 200%. It’s easy to understand why the business is so hot.”

Used cooking oil can legally be used to make biodiesel or animal feed in China, but, according to an article by Xinhua, it’s easier and cheaper to make cooking oil than biodiesel.

According to one journalist, the combined factors of Chinese cooking styles using plenty of oil and consumer demand for cheap restaurant food creates a market for gutter oil. Reducing the profit margin of gutter oil by adjusting the price of recycled oil for industrial use is one possibility for reducing the allure of processing gutter oil.

The current approach taken by the Chinese government, however, is to threaten those who trade in gutter oil with the death penalty. Qiu Baochang, head of the China Consumers’ Association, said “This shows that the country attaches great importance to ensuring food safety.”

This move has been questioned by some, with a legal expert from the Chinese Academy of Social Sciences suggesting that the death penalty should be handed down “with care” to gutter oil criminals as it is technically a non-violent crime.

The good news is that the government’s recent food safety campaign has resulted in legal oil processing businesses seeing a growth in the volume of raw material coming in, which means the used cooking oil is going where it’s meant to and not back onto people’s plates.

But with no accurate testing procedure available to differentiate good-quality oil from this ‘distilled sewage’, and no definite figures on just how rampant the industry is, eating out in China is still apparently a game of chance.