in China, both Mainland and Taiwan, illicit cooking oil which is recycled from waste oil collected from sources such as restaurant fryers, sewer drains, grease traps and slaughterhouse waste. This oil is often used in hotels, restaurants and wayside eateries in China
The issue is frequently found in People’s Republic of China. Reprocessing is often very rudimentary; techniques include filtration, boiling, refining and the removal of adulterants. It is then packaged and resold as a cheaper alternative to normal cooking oil. Another version of gutter oil uses discarded animal parts, animal fat and skins, internal organs, and expired or otherwise low-quality meat which is then cooked in large vats in order to extract the oil. Used kitchen oil can be purchased for between 859 and 937 dollars per ton while the cleaned and refined product can sell for 1,560 per ton. Thus there is great economic incentive to produce and sell gutter oil. It is estimated that up to one in every ten lower market restaurant meals consumed in China is prepared with gutter oil. This high prevalence is due to what Feng Ping of the China Meat Research Center has made clear: “The illegal oil shows no difference in appearance and indicators after refining and purification because the law breakers are skillful at coping with the established standards.”
The first documented case of gutter oil in mainland China was reported in 2000, when a street vendor was found to be selling oil obtained from restaurant garbage disposals.
The first documented case of gutter oil in Taiwan was reported in 1985. In subsequent investigation, 22 people were arrested for involvement in a recycling oil ring over 10 years based in Taipei. The worst offender was sentenced to 7 years in prison.
Additionally, some reported an earlier incident in Taiwan in the 1960s, where “Trench Oil” was imported from Japan to Taiwan and then used in food processing.
In September 2012, an ongoing investigation into the suspected use of gutter oil as a raw material in the Chinese pharmaceutical industry was revealed. A massive scandal involving 240 tons of gutter oil in Taiwan affecting hundreds of companies and thousands of eateries broke in September 2014, some of which may have been exported overseas.