THE latest headlines about swill oil, or gutter oil, dramatizes both the potency and impotence of technology.

Biofuel technology equips criminal suspects with the know-how to turn residual oil from sewer or slops into a substance so much like edible oil that inspectors now are hard pressed to come up with a technology to identify the swill oil for what it is.

There has been reported progress (October 21, Shanghai Daily) in swill oil testing, but it remains to be seen to what extent the progress can help solve the problem.

And the final solution may lie less with the scientists than every Chinese as consumer (or waster) of food.

The first reported discovery of swill oil can be traced to 2000, when a vendor in Liaoning Province successfully extracted edible oil from slops. From 2003 to 2005 there was considerable exposure of swill oil scandals.

But at that time swill oil processing was generally perceived to be too insignificant in scale to affect more than a very small minority.

The latest expose changed all this.

This March, acting on complaints about stench, local police in Ningbo, Zhejiang Province, came upon a site in a grove where kitchen waste and some slimy liquid were being stewed in a huge cauldron.

The police described the scene as more sickening than a village latrine, and said seeing the site would kill one's appetite for food for a whole day.

Four months of investigation ultimately helped police track down Liu Liguo, who owned a heavy-security biofuel company in Jinan, Shandong Province, which claimed it had a capacity to produce 40,000 tons of "biofuel" annually. Liu could make about 500 yuan (US$78) in profit by producing each ton of swill oil.

One employee recalled that once a barrel of processed oil fermented due to heat, and when the employee opened the lid to relieve the pressure, some oil splashed on him, and along with it was a piece of a woman's sanitary pad.

At least one four-star hotel was among the patrons of Liu's concoction.

Wishing to be dealt with leniently, Liu has already informed against more than 10 other companies engaged in the same business.

In Liu's case, police have detained 32 people for making and selling cooking oil originally dredged from gutters.

They formed a network covering the production, distribution and sale of swill oil that had been operating in 14 provinces.

Thanks to the development of biofuel technology, the likes of tech-savvy Liu could make "clean energy" out of gutter oil. The irony is that it is so clean that it stealthily finds its way back to restaurants and kitchens.

It is estimated that millions of tons of such oil are produced annually in China. Swill oil can be so clean that existing cooking oil testing methods fail to detect anything suspicious.

Once bottled and placed on supermarket shelves, they are virtually indistinguishable from other brands of oil more dignified in origins.

Furthermore, the relatively cheaper swill oil or oil adulterated with swill oil are more appealing to price-conscious residents or big consumers, like restaurants. The steadily soaring CPI adds to the appeal of swill oil.

Less costly

For instance, a middle-sized Chongqing hotpot restaurant may normally consume 20,000 yuan worth of oil a month, and obviously the restaurant has strong incentives to cut costs.

Large, more reputable restaurants may consider other factors.

One veteran cook interviewed by China Newsweek recently said a large restaurant might choose not to use swill oil, because it heats slowly, and usually turns blackish after being used a couple of times.

Crudely processed swill oil looks like cola, and gives off a bad smell. But once purified with calcium bicarbonate and neutralized with alkali, the oil begins to glisten like tea water, and is virtually indistinguishable from good oil to the naked eye - or detecting devices.

Only two of the 10 samples made of the swill oil found in the Ningbo crackdown appeared to be substandard when tested. So some restaurateurs may plausibly plead ignorance even after they have used the swill oil, especially when swill oil is added to good oil.

There are many complaints against food security watchdogs that fail to intervene earlier, and technological supervision departments that fail to function even when confronted with swill oil, but rarely, if ever, against residents and consumers, who are often perceived as "victims" rather than as miscreants chiefly responsible for wasting a stupendous amount of food in the first place.

Wasteful habits

As a result, the ultimate solution to the swill oil problem lies with ordinary residents, who prefer to have their dishes prepared with liberal use of oil. In a Chinese restaurant, wastefulness and extravagance are still interpreted as evidence of generosity.

The liberal use of oil in cooking is unnecessary from a health point of view. Today, with the specter of swill oil hovering near, that habit of eating rich, oil food takes on additional health risks.

According to statistics from Beijing, the amount of edible oil consumed in the city in 2009 totaled 600,000 tons, of which 15 percent ended up in the gutter - meaning a potential 90,000 tons of swill oil. About 25,000 tons of that oil were scooped from restaurant drains, and then sold to unlicensed private processors, because the "black" swill processors pay better and provide better services than the licensed collectors.

There are also implications for policy makers. Gutter oil, 98 percent-biodegradable, can be a clean alternative to diesel processed from petroleum.

German and Japanese governments reportedly collect gutter oil at subsidized prices and then turn it into fuel.

In the United States and South Korea there are also legal incentives for the use of biofuel.

But in China, legal gutter oil processing plants are being edged out of the market because they cannot pay as much as illegal gutter oil collectors.

It is reported that in Shanghai there are only 23 legal collectors, and in Beijing, only four. Naturally they could handle only a fraction of the gutter oil produced.

This year the Chinese government has offered tax breaks to help make biofuel from gutter oil, but it remains unclear how the subsidy could directly benefit the biofuel makers.