For the past 4-5 years, Southern Railway’s locomotive workshop in Perambur has been making bio-diesel out of free waste cooking oil from five star hotels in the city. The fuel has even been used as a blend to run the Diesel Electric Multiple Unit (DEMU) in Tiruchirapalli division.
The technique, which is one of its kind in Indian Railways, will be displayed at an international exhibition of railway equipment in New Delhi from October 14-16.
This method was shown at all workshops across the Indian Railways in 2004 and employs a simple process with materials that are reasonably cheap, railway officials said.
“The Perambur facility is the only one which continues to produce bio-diesel while others have discontinued,” said a senior official at the Perambur Loco Workshop.
The facility in Perambur can produce 5,000 litres of bio-diesel a month and present production varies from 1,500-2,000 litres, depending on the availability of waste oil.
The process is effective on two counts: first, the waste cooking oil, which would pollute the soil and water, is converted. Second, the bio-diesel produced is clean and doesn’t contain sulphur. This eliminates poisonous sulphur dioxide (SO2) emission from regular diesel burnt in the engine, the officials said.
Express visited the facility – a tiny shed in one of the lanes in the Loco Workshop and saw a demo of the chemical process.
Using 100 litres of waste oil, around 80-90 litres of bio-diesel was produced, the official said.
First, a sample of the oil is tested for percentage of fatty acids (FA test) by titrating it with sodium hydroxide (NaOH).
“Ideally, FA percentage should be less than four or the process would be complicated,” said the official.
Once the oil passes the FA test, it is heated to 65 degrees C with potassium hydroxide (KOH) using mechanical stirrers. This is the most important step, known as esterification, that separates the bio-diesel from the dark residue.
The viscosity, which shows how easily it flows as a fluid, is decreased nine times through this process. Thereafter it becomes an efficient fuel.
However, the bio-diesel so produced is alkaline. “This would damage engine parts and hence it needs to be neutralised using a water wash,” the official said.
Finally, the bio-diesel is once again heated to 110 deg C to remove as much water as possible. This entire process takes three days and requires only two or three trained hands.
Now the bio-diesel is used in Trichy DEMU and in shunting locos at Chennai Central. Officials said that there had been a steady increase in the number of hotels which supplied the waste cooking oil free. “When we began in 2004, there were only one or two. But now, we get it from the top 10 five star hotels of the city,” the official added.