It is not difficult and the process is simple for reporters to smelt waste oil in three days.

The so-called "gutter oil" generally refers to three kinds: old oil repeatedly fried, hogwash fat extracted from swill, and gutter oil extracted from floating oil in sewers. The refining processes of these three oils are similar: oil fishing, crude refining and refining, with little difficulty.

A technician from a famous edible oil manufacturer in Zhejiang said that any manufacturer of edible oil refining has the ability to mass produce "waste oil" without adding any equipment and technology.

There is no evidence in words, but the experiment proves it! From September 21st to 23rd, with the help of technicians, it took the reporter three days to refine about 250ml of golden yellow, clear and transparent gutter oil from a bucket of stinking and filthy floating oil.

The first step of the experiment: fishing for oil

The object of this experiment is floating oil in sewers, which is the so-called most authentic "gutter oil".

Oil fishing was carried out in the kitchen grease trap of a hotel in the city center on the morning of September 21st. The grease trap is under the manhole cover beside the kitchen. According to the requirements of environmental protection, all catering enterprises need to build it.

The tool for fishing oil is very simple, an oil drum and a digging rod. The front end of the digging rod is an aluminum bowl, and there are several small holes in the bottom of the bowl, which can filter water and leave oil.

When the manhole cover is opened, the gray-black floating objects exude a stench. Under the stirring of the pole, a few beans can be seen from time to time in the corroded garbage, which proves that they really come from the kitchen.

The second step of the experiment: rough refining

The reporter found an abandoned brick house in Yuhang, built a primitive stove with three bricks, set up an asphalt bucket, poured in a big bucket of waste oil raw materials, ignited and refined.

The fire burned for about twenty minutes, and the liquid in the oil drum boiled completely. The originally turbid liquid gradually became clear, and a thick layer of oil was floating after skimming the surface impurities.

Put it out, and after cooling, pick up the grease on it. These oils are the newly processed gutter oil, which is dark red, looks like old oil and stinks.

The third step of the experiment: refining

After rough refining, the waste oil can’t be put on the table, but also impurities, sediments, decoloration and deodorization should be separated. This time, the method of fine processing of edible oil was fully referenced.

We took 5 liters of crude cooking oil boiled by indigenous method as raw material of crude oil and sent it to a famous large edible oil manufacturer in Zhejiang. Factory technicians Xiao Jing and Xiao Zou (a pseudonym) clearly stated that these crude oil raw materials can be completely refined on their production lines.

"The alkali refining, water washing, decoloration and deodorization of waste oil are exactly the same as the fine processing of edible oil, but the deodorization link is not perfect in the laboratory."

Because it is extracted from the corrupt and acidified floating oil, gutter oil contains a lot of acidic substances, which can only be neutralized by adding alkali, that is, alkali refining.

After adding alkali, the waste oil quickly became turbid, from deep red to yellow similar to milk tea. After stirring, many white coagulants appeared.

"White coagulum is soap feet, which is a good raw material for making soap." Xiao Zou said.

After alkali refining, it is washed with water. The purpose is to accelerate the separation of oil and soapstock. It is very simple to add 10% salt water.

When it was placed in the early morning of the next day, the separation of oil and soap was completed. At this time, although the sour smell was reduced a lot, the color of the gutter oil was still dark red and opaque.

Decolorization is the most critical step in refining waste oil. This requires activated clay, which is an odorless, tasteless and nontoxic adsorbent.

Adding activated clay into the dark red oil in proportion, fully stirring, and turning the whole bottle of oil into black; Let it stand for 30 minutes at the temperature of 110℃-120℃, and then filter out the white clay, and a miracle will appear.

The original dark red and opaque gutter oil has become golden in color, clear and transparent; The tasteless clay, after filtering out, became black and smelled sour.

The last step of refining is deodorization.

Deodorization is also the last step of normal edible oil finishing. After this processing, the oil becomes completely odorless, but it needs to be carried out in a vacuum environment and cannot be operated in the laboratory.

Xiaojing took out a bottle of edible essence, dropped three or four drops into the gutter oil, and smelled it again, and it had no sour smell.

"If I add peanut essence, it smells like peanut oil." Xiaojing said.