For health reasons, consumers are advised to reuse cooking oil only once and discard it after the second use.
Delicious deep-fried foods like these bananas use a large amount of oil. THANARAK KHOONTON
A recent Consumer Protection Foundation report alleging that an outlet of a leading food chain used old cooking oil has worried the public.
If the oil is used repeatedly, it is sure to affect its quality with the increase in volume of polar compounds, which can lead to high blood pressure and heart attacks.
Using oil less frequently may be expensive for consumers and food vendors, while finding the best way to dump the greasy fluid without environmental impacts is also crucial.
Now there is a choice. They may sell used oil to petroleum firms, while food manufacturers may turn the oil to biodiesel themselves.
Biodiesel is one alternative fuel that has been promoted by the state. As of September last year, there were 14 companies making 5.2 million litres daily of biodiesel from vegetable oil plants such as palm, coconut, soybean and jathopha.
Only two, Bangchak Petroleum Plc and Bangkok Produce Co, employ used cooking oil as raw material, according to the Department of Alternative Energy Development.
The department says 150 million litres of cooking oil is used every year in Thailand, most of it reused and disposed of improperly with severe ecological effects.
Bangchak has a project to buy used oil from retail users and food vendors.
Public relations director Chaveewan Kiatchokchaikul said the company produces about 350,000 litres per day of biodiesel, mostly from crude palm oil. About 50,000 litres is produced from used cooking oil.
"Every weekend, staff are sent out to collect used cooking oil from 161 fresh markets in Bangkok in partnership with the Bangkok Metropolitan Administration," she said.
Also, 25 Bangchak petrol stations in the capital are venues for consumers to sell used oil.
Ms Chaveewan said Bangchak also gets the raw material from big corporations such as Thai Airways International and vendors selling food at Central department stores.
She said the quality of used oil from these corporations is much better than that of oil collected from small vendors.
Bangchak started its project in 2007 as part of its campaigns related to corporate social responsibility and a commitment to be a leader in renewable energy. It now pays 13 baht per kilogramme for used oil.
The volume remains small due to competition from other industries that also need used oil for making soap and animal feed.
Bangchak only collects used oil at areas in the capital and has insufficient staff to extend the service nationwide.
Bangkok Produce, a chicken production unit of Charoen Pokphand Foods Plc (CPF), also converts used oil into biodiesel through the transesterification chemical conversion process.
The method uses methyl alcohol for the chemical reaction. Glycerin is separated as a byproduct, while cleaning the fluid with water is the final step that produces clean biodiesel and wasted fats that may be used to make soap.
Kritsada Tosathum, manager of CPF's systematic engineering department, said the biodiesel operation is carried out as a way to dispose of used oil and convert it to renewable energy.
The food company produces about 200,000 litres of used oil each month that it converts to about 142,000 litres of B100 biodiesel.
The investment in making biodiesel from vegetable oil is low at 2 million baht, but it helps the firm to reduce dependence on diesel by about 7.98 million baht every month.
Renewable energy is part of the government's 10-year Alternative Energy Development Plan (2012-21) that aims to increase the use of alternative energy from 7,413 ktoe (thousand tonnes of oil equivalent) in 2012 to 25,000 ktoe in 2021 or 25% of power consumption.
Converting used cooking oil to biodiesel is a three-step process.