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BioBot 20 countertop diesel processor converts waste cooking oil into biodiesel


February 9, 2013

UK-based Biobot has introduced a simple chemical reactor for converting used kitchen oils into biodiesel fuel at home (Photo: Shutterstock)

UK-based Biobot has introduced a simple chemical reactor for converting used kitchen oils into biodiesel fuel at home (Photo: Shutterstock)

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One difficult aspect of a greener lifestyle involves disposal of used cooking fats. Most people either pour it down the drain, where it can lurk for years while conspiring to clog your pipes, or pour it in the yard, where it attracts pests of various sorts looking for a free meal. Recycling is obviously a better option, and to this end the BioBot 20 tabletop diesel processor – a (relatively) simple chemical reactor for converting used kitchen oils into biodiesel fuel at home – has been introduced by UK-based company Biobot.

How biodiesel is made

Widely used for a host of purposes, highly-efficient diesel engines power a good fraction of the world's transportation, industry, and power generation needs. Diesel fuel is denser than gasoline, and has 11 percent larger energy content per liter. Nearly a trillion liters of diesel fuel are used each year worldwide, which releases about 10 percent of the world's anthropogenic CO2 emissions.

Biodiesel fuels offer a greener alternative to the use of petroleum-derived fuels. Otherwise known as fatty-acid methyl ester (FAME), biodiesel is derived from waste vegetable oils, and is close to carbon-neutral in use. Worldwide, about 20 billion liters of biodiesel are made yearly, with the potential of a fivefold increase without diverting oil away from food uses. Compared to petrodiesel, biodiesel has better lubrication ability, higher cetane rating (less diesel knock), and essentially no sulfur, making it a desirable replacement fuel.

Transesterification converts A (methyl alcohol) and B (vegetable oil) into C (glycerin) and D (biodiesel) (Image: B. Dodson)

The process of making biodiesel is called transesterification. Vegetable oil is largely made of triglycerides, which contain three fatty acid esters bound to a single glycerine molecule. In the transesterification process, triglycerides are reacted with a mixture of methyl alcohol and sodium hydroxide so that the fatty acid esters break off from the glycerine molecule, and are capped with the methyl group from the methyl alcohol. Potassium hydroxide can also be used, and is preferred by many biodiesel producers.

The BioBot 20 tabletop diesel processor

Perhaps as much an educational tool as a practical way to produce biodiesel, the BioBot 20 tabletop diesel processor has a capacity of 20 liters per batch. It's operation is shown in the video below, but briefly you fill the reaction chamber with used vegetable oil, then heat the oil to a designated temperature while agitating the oil with a built-in hand operated mixer. When the oil comes to temperature, a small amount is tested to determine the amount of free fatty acids it contains. This determines the amount of sodium hydroxide catalyst is required to process the batch.

The desired amount of catalyst is added to four liters of pure, dry methanol, and the combination is mixed until the catalyst dissolves in the methanol, forming sodium methoxide. The sodium methoxide is stored in a special tank which pumps it into the reaction chamber so that it need not be handled any more than necessary (it is very corrosive).

The pumping takes place while the oil is hot and being agitated. The reaction proceeds slowly, often taking 12-24 hours to finish. At that point the glycerin has accumulated at the bottom of the reaction chamber, from which it is drained using a tap at the bottom of the reaction chamber. The remainder is biodiesel.

The raw biodiesel must be washed before use to remove soaps, excess methanol, residual sodium hydroxide, free glycerine and other contaminants. This is accomplished by washing it with water. In the BioBot 20, water is pumped to a spray mister at the top of the reaction chamber. Agitation during washing is not recommended, lest soap result from a batch having free fatty acids. The water does not dissolve in the biodiesel, but as it passes through it will pull out contaminants. The water wash process is repeated until the biodiesel is clear, at which point in time it is reheated to remove residual traces of water.

Is all this worthwhile? Depends on how you value your time, but if the vegetable oil is waste cooking oil, it at least is free. The four liters of methanol costs about US$3.50, while the sodium hydroxide might cost US$0.50 or so. If the biodiesel yield is 15 liters, this corresponds to less than €0.25/liter or US$1.00/gallon. There are other minor expenses, but overall brewing home-made biodiesel can be a profitable activity. The BioBot 20 sells for £415, or about US$655.

Source: Biobot

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer. All articles by Brian Dodson

Just exactly the process that my dad and I used except did it in a 2000lt milk vat. The process and nearly the time, is the same making 20lts as to 1000lts. When washing the oil used 50/50 water to oil, hence why only made 1000lts of Bio in a 2000lt vat. The milk vat is insulated so made it easier to heat oil and keep it warm enough to poor off the glycerin 24hrs later. Took a little bit to setup the mixers but once done it was worth while. Big note, when reheating to get water out of oil don't exceed 55 degress Celcius or you make varnish, which your engine doesn't like. We made a vaccum chamber which helped boil off water at a lower temp. The Bio is like a cleaner to your cars fuel system, so when you start clogging filters it's the bio cleaning the crud from what the standard Diesel leaves behind. So if you make clean bio, over time your system will clean out and you won't have to keep changing filters. BUT don't run it in Common rail engines because if you make one slight mistake on your batch you are up for big bucks at the mechanics. The old school diesels run like a charm on it, smoother and quieter. It worked out costing roughly .25c/ltr, we pay $1.45/ltr at the station.


I know a guy who was told by MickieBenZ of Portland to not run biodiesel in his 2009 R class, he did it anyway, ruined the engine, they did him a favor and sold him a new engine at cost, $11,000, new diesels are very sophisticated, shoot, you can have a 2010 VW TDI Jetta running in the shop, no diesel smell, no diesel noise, very impressive. In other words, do not run bio D in a car made after about 2000, fuel leaks, destroyed pumps, worst case engine.

Bill Bennett

...or you could not use cooking oil. The only oil I use goes onto salads and pasta. I can't remember the last time I fried something in oil. Sometime in the 60's I think.


Biodiesel is better for engines than petrodiesel but not necessarily for fuel systems which may contain rubber. Biodiesel eats rubber. Just make sure all rubber seals and hoses are neoprene or some other fuel-proof material.

Also make sure you wash AND DRY the fuel thoroughly. Get every last trace of soap glycerine and water out of it.

KOH is better than NaOH because the glycerine is less viscous and easier to drain off when cold. Also potassium is a plant nutrient. Unfortunately the price of KOH has gone through the roof since the homebrewers started buying heaps of it.

Lastly, if you are not making the stuff in 100 litre batches you are unlikely to ever have enough.


Diesel engines are so delicate, so easily offended and so GDF expensive to maintain, the money you saved by using diesel, in stead of Petrol, just went straight to the maintenance cost of the engine...

Michiel Mitchell

So this is cool man.

What about a membrane for cleaning and drying. These new super hydrophobic and oligophobic substances are making me think this morning. I found a peer reviewed article which noted "membranes with hygro-responsive surfaces, which are both superhydrophilic and superoleophobic, in air and under water. Our membranes can separate, for the first time, a range of different oil–water mixtures in a single-unit operation, with >99.9% separation efficiency, by using the difference in capillary forces acting on the two phases." This membrane is designed to reduce the cost of seperating water oil mixtures yet I think it would work well with this whole solution. So if you include the solar panels or wind power for the heat production You get a very viable alternative fuel system.

Spriscilla the Queen of the Ocean

So, oil becomes diesel... So what? Burning something to drive or generate energy other than cooking and heating must be prohibited! Especially in Internal Combustion Engines, shouldn't we stop wasting valuable time in electrifying those engines? (in anticipation of the question, where will the electricity come, coal or gas? Non, won't have to! But even if it did, an electric motor is 5 times more efficient than an ICE to convert energy into kilometers)


re; sinan

I am not going to buy a car that I can't get out of the way of a hurricane in. Where are you going to get the extension cords?


I think production of biodiesel from waste oil is best left to dedicated small businesses, who have the time to collect from restaurants and fast food outlets, and can go through the labourious processes necessary- this machine, though laudible, takes far too much effort- plus you'd either have to fry yourself into a coronary or go scavenging used oil to make it worthwhile.

I once ran an old Vauxhall Astra (Opel Kadett with British badges) on new veg oil and about 20% mineral diesel- ran very well.

I know that some bus fleets in the UK have had major problems using part biodiesel in their fleets as it eats rubber seals (you'd think those companies would carry out preventative maintainance to avoid that effect but no, they'd rather leave their passengers constantly inconvenienced by frequent breakdowns).


Responding to sinan, the problem isn't energy conversion, but storage. The best lithium ion battery stores only about 10% of the energy per volume of either gasoline or diesel.

Pat Kelley

OK, Twenty liters per batch? That should be enough to power that tiny little "palm top" washing machine we saw the other day.

Bruce Williams

Almost all diesel now has biodiesel already in it ever since they took the sulfur out of diesel as the sulfur use to lube the FI. So once they removed it they needed to replace the lube and BD does just that.

All new diesel engines should run on biodiesel without a problem. Some older ones had seal issues but not even many of them.

Remember Diesel started out using veg oil as fuels as there was no petro diesel then.

Plus most early engines were designed to run on fuels that could be made like the Model T running on ethanol stock.


20 liters is about all the waste fat that anybody would want to store so the capacity sounds reasonable to me. however if your willing to modify your diesel engines fuel system simply washing/drying and filtering the waste fat works well and you don't have to figure out what to do with the glycerine but it does make great soap.


@Pat Kelley, well, I have figures even more discouraging than yours, comparing the storage capacity of fossils to battery storage. But, at the same time we've come a long way from Lead Acid (10x for Lithium, as well as the abundance, nontoxic, recyclable nature of it) so that shouldn't be a brake on advancing the electrification of transport. 160 km of range is more than enough for 90% of drivers (other 10%, people like SlowBurn are encouraged to continue burning whatever they like) Although I'd prefer them keeping some of the emissions inside the car, instead of poisoning others.


If you already own a business that uses cooking oil to prepare food, this would be a good step towards using it to create fuel, although you would need more than one or a larger unit to keep up with the oil you would have each week. I've seen a food truck that uses it's own old fry oil to make the bio-diesel that is used to fuel the truck. Also, you can purchase a diesel generator that is made to run on bio-diesel. I plan on buying one as back up power for the house I plan to build, which will use alternative energy sources for power.

Gene Jordan


Commercial diesel may have some biodiesel added, but it won't be from waste cooking fat (more likely to be cheap palm oil from South-East Asia for which much forest is slashed and burned to make way to grow it), and whilst modern diesels can cope with commercial diesel with some added biodiesel, they certainly can't cope with 100% 'home brew' such as this kit is designed to make.


Season 1, Episode 1 of the British show Top Gear gave the perfect recipe for making your own bio diesel without having to spend a fortune on a machine to do it! For each liter of veg oil you add a teaspoon of white spirit or ether. At the end of the episode they run a car on their mixture for lap after lap after lap around the track! Restaurant jobs may not pay too well, but if you can be the person who cleans the fryers every night, you could likely take enough used oil that you could run your vehicle indefinitely on fryer grease!

Joel Bauman

I would rather take my oil to a processing plant and get credit because if your big enough you can do it with more quality equipment and make sure that you don't burn the wrong stuff. If the quality is indeed higher I wouldn't mind paying a little more for the better quality.

I wish there was places where you could go to do this. I only know that there are places for commercial places like McDonald to do so and I know Saudi Arabia has a close to 100% use of bio-diesel like this but in large commercial converters.

Ben O'Brien

I see. So that is how they make biodiesels deriving from vegetable and food oils. Amazing how such an oil can be used in engines when it is supposedly for humans. I'd like to know more about biodiesels including their benefits and disadvantages.

Jacob Wadsworth

US the reason most distributors have added biodiesel to heating oils and diesel fuel is because they get an alternative energy dredit on federal taxes as long as they incorporate at least 5% biodiesel, its not because they are going green, it boils down to money for them.

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