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.