Will you be filling your tank at the chip shop?

The process of converting vegetable oil into fuel is called Transesterification. Transesterification of a vegetable oil was conducted as early as 1853 by scientists E. Duffy and J. Patrick.

oil-bottlesIn organic chemistry, transesterification is the process of exchanging the alkoxy group of an ester compound with another alcohol. These reactions are often catalyzed by the addition of an acid or base.

Transesterification is used in the synthesis of polyester, in which diesters undergo transesterification with diols to form macromolecules. For example, dimethyl terephthalate and ethylene glycol react to form polyethylene terephthalate and methanol, which is evaporated to drive the reaction forward. The reverse reaction (methanolysis) is also an example of transesterification, and has been used to recycle polyesters into individual monomers (see plastic recycling).


Thousands of people in the UK are now making their own biofuel. As oil price and duty rises will push diesel prices well beyond the £1-a-litre mark, and as the fueld road duty gets applied to marine diesel – despite the 60/40 rule – should boaters now take the biofuel option seriously?

In the UK it is now legal to make up to 2,500 litres of your own biodiesel, enough to run the average family car, or your thirsty motor yacht, without having to pay tax.

Home brewing

Dan Purkis, a consultant engineer, puts home-brewed fuel into the tanks of his 4×4, even though he is based in Aberdeen – the oil capital of the UK. He admits that messing about with old chip fat is not for everyone but adds: “It’s interesting and fun and it reduces my impact on the environment? He told the BBC’s You and Yours programme: “No special tools were required and nothing was beyond the ability of a typical DIY Merc-Biodiesel 3enthusiast. Most of the parts were bought second hand or salvaged from scrap yards.

“I recycle used vegetable oil from a local hotel. They throw away between 50 and 100 litres a week which would otherwise go to landfill.”

Once he gets it home, he puts the oil through a series of refinements:

* Allows sediment in the oil to settle to the bottom of the bottle
* Pumps and filters the top 70% of the oil; it is pure enough to put straight into his car
* Treats the remaining sludge and converts it into biodiesel by adding methanol and caustic soda
* Heats the oil, causing it to react with the caustic soda

The waste product from this process is glycerin, which has to be washed out of the biodiesel with soap and half-water to half-fuel. He then composts the glycerin.

Mr Purkis says his car runs better on biodiesel: “It’s smoother – better lubricated.”

biodieselSo why dont we all do it now?

Well there are several potential problems:
1). The fat will not flow through the fuel supply pipes
2). The fat clogs in the fuel filter
3). The fat forms an emulsion in the return pipe
4). The fat will not burn effectively
5). The engine will not want to start on the fuel from cold

All of these problems can be overcome. You can do this by modifying the vehicle fuel supply, or modifying the engine itself or by modifying the fuel. Check out this site for a complete run down on overcoming all these problems..

But is it carbon friendly ?…

Well according to this site which is dedicated to low carbon living

* Biodiesel made locally from waste oil: 1 litre = 0.6 to 1 kg CO2
* Biodiesel made locally from waste oil and with ethanol distilled from plant materials locally: 1 litre = 0kg CO2 🙂
* Used vegetable oil: 1litre = 0kg CO2 🙂

If you are making biodiesel and wondering what the CO2 impact is:

* Methanol made from natural gas: 1 litre = 4.6kg CO2
* Methanol made from coal: 1 litre = 9kg CO2
* Methanol / Ethanol made from vegetable sources: 1 litre = 0kg CO2 🙂

If you are looking for something to do on 17/18 October you can joing thousands of enthusiasts at the Biofuels Expo to get info on how to set up your own filter system. This is the largest bioenergy event in Europe with over 100 Exhibitors showcasing the latest developments in the Biofuel and Bioenergy markets.






4 thoughts on “Will you be filling your tank at the chip shop?

  1. Hi,just found your Blog when i google something and wonder what webhosting do you use for your blog,the speed is more faster than my wordpress, i really want to know it.will back to check it out,thanks!

  2. i hope that we would be able to mass produce Biodiesel in the near future and i also hope that it would get cheaper

  3. Was actually doing some browsing and came across this site. Have to say that this article is what I was searching for! Keep up the good info. Will be following your articles

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