measuring out lye and chemical supplies used for a
Sample of used
oil about to be titrated.
Color of titrated
liquid sample when at the correct pH.
amount of lye.
under transesterifyer vessel.
View of sodium
methoxide mixer (left) and transesterifyer vessel (right).
of sodium methoxide mixer being drained into transesterifyer vessel (note
Valve on bottom
of transesterifyer vessel user to decant out more dense glycerin from less
Fuel pump and
filters -- these are used last, after soapy residues and lye have had time
to settle out of biodiesel.
trailer-mounted processor: propane tank is for heating grease, PVC
containers on either side are soap settling tanks for biodiesel prior to
pumping through filters. Pick-up line for filter pump is inserted into
tank only deep enough to siphon esters and not soaps on bottom.
ready for the fair... Mike promotes biodiesel wherever he can.
Mike Pelly lives in the US North West. "I live for renewable energy
projects," he says. Mike's been making his own biodiesel fuel from
waste cooking oil for the last five years, using it in several different
cars. He finds it "far superior" to fossil-based diesel fuel.
Mike sent us a full report on how he makes biodiesel. "It's a result
of my work over the past five years along with contributions from other
experimenters," he said. "Pass it along to anyone you
please." Here it is.
From Used Kitchen Grease or Waste Vegetable Oil
by Mike Pelly
This is how to make your own biodiesel fuel from used cooking oil. The oil
-- waste vegetable oil (WVO), used fryer grease, animal fats, lard -- is
often free for the taking. All you need is a few common chemicals and some
equipment you can easily buy or make yourself. The result is a cheap,
clean-burning, non-toxic, renewable, high-quality diesel motor fuel you
can use in your car without modifications.
fuel from used kitchen grease"
by Mike Pelly in the Jan/Feb 2001 issue of Countryside
Wear proper protective gloves, apron, and eye protection and do not inhale
any vapors. Methanol can cause blindness and death, and you don't even
have to drink it, it's absorbed through the skin. Sodium hydroxide can
cause severe burns and death. Together these two chemicals form sodium
methoxide. This is an extremely caustic chemical. Wear a mask and full
body covering for safety, that means chemical-proof gloves with cuffs that
can be pulled up over long sleeves -- no shorts or sandals. These are
dangerous chemicals -- treat them as such! Always have a hose running when
working with them. The workspace must be thoroughly ventilated. No
children or pets allowed.
Waste vegetable oil (WVO) -- used cooking oil, fryer grease, animal fats,
Methanol (CH3OH) -- 99%+ pure
Sodium hydroxide (NaOH -- caustic soda, lye) -- must be dry
Isopropyl alcohol (rubbing alcohol) -- 99%+ pure
Phenolphthalein solution (not more than a year old, kept protected from
strong light) -- "Phenol" or "Phenol Red" from
swimming pool or hot tub supply stores may not be the same as
phenolphthalein; it can be used but the directions for use may be
WVO to remove any food scraps or solid particles.
procedure is called transesterification, similar to saponification. Sound
familiar? Saponification is soap making. To make soap you take a
transfatty acid or triglyceride (oil or kitchen grease) and blend it with
a solution of sodium hydroxide (NaOH, caustic soda or lye) and water. This
reaction causes the ester chains to separate from the glycerine. These
ester chains are what becomes the soap. They're also called lipids. Their
unique characteristic of being attracted to polar molecules such as water
on one end and to non-polar molecules like oil on the other end is what
makes them effective as soap.
In transesterification, lye and methanol are mixed to create sodium
methoxide (Na+ CH3O-). When mixed in with the WVO this strong
polar-bonded chemical breaks the transfatty acid into glycerine and also
ester chains (biodiesel), along with some soap if you're not careful (more
on that later). The esters become methyl esters. They would be ethyl
esters if reacted with booze (ethanol) instead of methanol.
Figures 1-3 show these two reactions. The zigzag lines in the triglyceride
diagram (Figure 1) are shorthand for carbon chains. At both ends of each
line segment is a carbon atom.
In Figures 2 and 3 these
zigzags are shorthanded as R1, 2 and 3.
Filter the WVO to remove
food particles. You may have to warm it up a bit first to get it to run
freely, 95 deg F (35 deg C) should be enough. Use a double layer of
cheesecloth in a funnel, or a restaurant or canteen-type coffee filter.
Removing the water
Many people heat the WVO
first to remove any water content. Waste oil will probably contain water,
which can slow down the reaction and cause saponification (soap
formation). The less water in the WVO the better.
and Joe, an organic farmer who makes 40 gallons of biodiesel a
week for the farm truck and tractor.
This is how they do it. Raise the temperature to 212 deg F (100 deg C),
hold it there and allow any water to boil off. Use the mixer to avoid
steam pockets forming below the oil and exploding, splashing hot oil out
of the container. Or drain water puddles out from the bottom as they form
-- you can save any oil that comes out with the water later.
When boiling slows, raise the temperature to 265 deg F (130 deg C) for 10
minutes. Remove heat and allow to cool.
You may be lucky and find a regular source of WVO that doesn't need to
have the water boiled off, in which case don't do it -- boiling means
extra energy and time. Personally I don't boil off the water first, I'd
rather avoid the extra step in the process and save the energy it uses.
But unless you're sure, it may be better to be on the safe side.
To determine the correct
amount of lye required, a titration must be performed on the oil being
transesterified. This is the most difficult step in the process, and the
most critical -- make your titration as accurate as possible.
The lye must be dry -- keep it away from water, store it in an airtight
Make up a solution of one gram of lye to one liter of distilled water.
Make sure it dissolves completely. This sample is then used as a reference
tester for the titration process. It's important not to let the sample get
contaminated, it can be used for many titrations.
Mix 10 milliliters of isopropyl alcohol in a small container with a 1
milliliter sample of WVO -- make sure it's exactly 1 milliliter. Take the
WVO titration sample from the reaction vessel (Figure 5 #1) after it's
been warmed up and stirred.
Add to this solution 2 drops of phenolphthalein, an acid-base indicator
that's colorless in acid and red in base.
Phenolphthalein has a shelf life of about a year, it is very sensitive to
degradation by light so after a while it will start giving erroneous
Using a graduated eye dropper (with increments marked in tenths of
milliliters) or some other calibrated instrument (from medical supply
outlets), while carefully keeping track of the amounts, drop measured
amounts of the lye/water solution a couple of tenths of milliliters at a
time into the WVO/isopropyl/phenolphthalein solution.
Follow each drop with vigorous stirring of the solution. In cold weather
the WVO might congeal and not work so you might need to do the titration
in a heated room. If conditions are right eventually the solution turns
pink (magenta), and stays pink for 10 seconds. This is the indicator color
for a pH range of 8-9 (see the photograph in the left column of this page,
"Color of titrated liquid sample when at the correct pH"). It's
important to find the exact amount, to just reach this pH without dropping
in too much!
It's a good idea to do this entire process more than once to ensure that
your number is correct. I've found that depending on the type of WVO, how
hot it got in the fryer, what was cooked in it and how long it was used,
the amount of lye/water solution needed to titrate it is usually 1.5 to 3
milliliters. You can also use litmus paper or a digital pH tester instead
of the phenolphthalein. Try it with fresh cooking oil from your kitchen
too, it should need much less lye to reach pH 8-9.
The next step is to
determine the amount of lye needed for the reaction. Take the number of
milliliters derived from the titration and multiply by the number of
liters of WVO to be transesterified.
There is one more thing to be included in the calculation. Every liter of
neat vegetable oil (fresh -- never been cooked) needs 3.5 grams of lye for
the reaction. So for every liter of WVO to be transesterified add an
additional 3.5 grams of lye.
Example: The titration determined that it took 2.4 milliliters to reach pH
8-9 and you'll be transesterifying 150 liters of oil.
2.4 grams times 150 liters equals 360 grams lye
Plus 3.5 grams times 150 liters equals 525 grams lye
360 + 525 = 885 grams lye
If the titration result was 1.8 milliliters to reach pH 8-9, the final
amount of lye needed for the reaction would be 795 grams.
I've found over time that the number of grams of lye needed per liter of
WVO has generally been between 6 and 7.
The first few times you do
this process or if you're planning on transesterifying a lot of WVO it is
a good practice to first try out your lye amounts on a 1 liter batch in a
kitchen blender. This works really well and you don't need to heat up the
WVO too much, just enough so it will spin well in the blender. Blenders
are very thorough at mixing the ingredients so heating is not as critical.
Start by mixing up the lye and methanol in a blender (one that will never
be used for food again). First make sure the blender and all utensils used
are dry. Forming the exothermal sodium methoxide polar molecule will heat
up the blender container a bit. Keep mixing until all the lye has been
Once the sodium methoxide is prepared, add to the blender 1 liter of WVO.
Make certain all your weights and volumes are precise. If you're unsure of
the titration result numbers then use 6-6.25 grams of lye per liter of
used WVO, or 3.5 grams for fresh vegetable oil. Blender batches need only
be run for about 15-20 minutes for separation to be completed before
switching off. The settling takes some time to complete. The solution can
be poured from the blender into another container right after switching
off the blender.
It is good to do a few batches with varying amounts of lye recorded so
later when checking results one can choose the lye quantity that did the
When too much lye is used the result can be a troublesome gel that is
tough to do anything with. (See Glop
soap.) When not enough lye is used the reaction does not go far enough
so some unreacted WVO will be mixed with the biodiesel and glycerine. This
will form three levels with biodiesel on top above unreacted WVO with
glycerine on the bottom. If there is too much water in the WVO it will
form soaps and settle right above the glycerine forming a fourth level in
the container. This layer is not too easy to separate from the unreacted
WVO and glycerine layers.
Preparing the sodium methoxide
Generally the amount of
methanol needed is 20% of the WVO by mass. The densities of these two
liquids are fairly close so measuring 20% of methanol by volume should be
about right. To be completely sure, measure out a half-liter of both
fluids, weigh, and calculate exactly what 20% by mass is. Different WVOs
can have different densities depending on what type of oil it originally
was and how long it was used in the deep fryer.
Example: When transesterifying 100 liters of WVO, use 20 liters of
The methanol is mixed into a solution with the sodium hydroxide (lye),
creating sodium methoxide in an exothermic reaction (ie it gets warm from
bonds forming). Keep all utensils the lye comes in contact with as dry as
Treat sodium methoxide with extreme caution! Do not inhale any vapors! If
any sodium methoxide gets splashed on your skin, it will burn you without
your feeling it (killing the nerves) -- wash immediately with lots of
water. Always have a hose running when working with sodium methoxide.
Sodium methoxide is also very corrosive to paints. Lye reacts with
aluminum, tin and zinc. Use glass, enamel or stainless steel containers --
stainless steel is best. Used restaurant equipment supply stores and scrap
metal recycling yards are two good places to look for this type of
equipment. Braze on plumbing fittings for drains, etc. where needed.
Heating and mixing
Pre-heat waste vegetable oil
reclaimed from a restaurant's waste grease barrel to 120-130 deg F (48-54
A propeller or paint stirrer coupled to a 1/2-inch electric drill held
securely in a jig works fine as a mixer.
Too much agitation causes splashing and bubbles through vortexing and
reduces mix efficiency. There should be a vortex just appearing on the
surface. Adjust the speed, or the pitch or size of the stirrer to get the
If you want a quieter processor, an electric pump plumbed to form a mixing
loop for stirring the WVO would do a nice job. Mount the pump above the
level that glycerine will gel at to prevent clogging up the pump (see
Add the sodium methoxide to the WVO while stirring; stir the mixture for
50 minutes to an hour. The reaction is often complete in 30 minutes, but
longer is better.
The transesterification process separates the methyl esters from the
glycerine. The CH3O of the methanol then caps off the ester chains and OH
from the NaOH (lye) stabilizes the glycerine.
Settling and separation
Allow the solution to sit
and cool for at least eight hours, preferably longer. The methyl esters --
biodiesel -- will be floating on top while the denser glycerine will have
congealed on the bottom of the container forming a hard gelatinous mass
(the mixing pump must be mounted above this level).
An alternative method is to allow the reactants to sit for at least an
hour after mixing while keeping the brew above 100 deg F (38 deg C), which
keeps the glycerine semi-liquid (it solidifies below 100 deg F). Then
carefully decant the biodiesel.
This can be done by draining the reactants out of the bottom of the
container through a transparent hose. The semi-liquid glycerine has a dark
brown color; the biodiesel is honey-colored. Keep a watch on what flows
through the sight tube: when the lighter-colored biodiesel appears divert
it to a separate container. If any biodiesel stays with the glycerine it
is easy to retrieve it later once the glycerine has solidified.
If you left the mixture in the tank until the glycerine gelled, reheat the
tank just enough to liquify the glycerine again. Don't stir it! Then
decant it out as above.
Figure 4 shows one example of a system for separating two liquids with
different densities. This could make a good pre-filter or be used to
separate oils, soap and glycerine/esters goop. Marine/boat fuel cleaning
systems do a good job of filtering.
Figure 5 shows the reaction vessel (#1) where the WVO is mixed (also could
be done with a pump) and heated. Heating is accomplished by (#2) a
hotplate, propane-burner, or a diesel stove would work well.
A proposed alternative using very little electricity is illustrated in
Figure 6. This system would use a furnace-type burner run on reclaimed
esters to heat its reaction vessel. The vessel's stirring action is
created by thermo inversion currents generated by the vessel's external
cooling tubes and a baffled exhaust vent that runs up through its center.
Figure 5 also shows a blender (#3) used to mix up the sodium methoxide.
When making 16 liter (5 gal) batches, I use a yard-sale glass blender for
the sodium methoxide solution (and for nothing else!), but I can't fit it
all in at once, so I measure out three separate portions.
The glycerine from WVO is
brown and usually turns to a solid below about 100 deg F (38 deg C).
Glycerine from fresh oil often stays a liquid at lower temperatures.
Reclaimed glycerine can be composted after being vented for three weeks to
allow residual methanol to evaporate off or after heating it to 150 deg F
(66 deg C) to boil off any methanol content (the boiling point of methanol
is 148.5 deg F, 64.7 deg C). The excess methanol can be recovered for
re-use when boiled off if you run the vapors through a condenser.
Another way of disposing of the glycerine, though a great bit more
complicated, would be to separate its components, mostly methanol, pure
glycerine (a valuable product for medicines, tinctures, hand lotions,
dried plant arrangements and many other uses -- see Glycerine)
and wax. This is often accomplished by distilling it, but glycerine has a
high boiling point even under high vacuum so this method is difficult.
I was able to find someone who could use my glycerine (for dried flower
arrangements) through the Industrial Materials Exchange (IMEX) in Seattle.
IMEX has a publication that comes out every other month with listings,
looking for and offering all types of surplus industrial materials. Many
areas have similar exchanges. http://www.metrokc.gov/hazwaste/imex/
The glycerine by-product makes an excellent industrial-type
degreaser/soap. One way to purify it is heat it to 150 deg F (65.5 deg C)
to boil off excess methanol, making it safe for skin contact (take
precautions with fumes). Once the glycerine is back to a liquid the
impurities sink to the bottom and the color will become a more uniform
dark brown. This can be cut with water leaving it a tan color, less
concentrated and softer and easier to handle when washing hands. Produced
this way the degreaser could be sold in squeeze or pump dispensers.
Other ideas for disposing of the glycerine are breaking it down to usable
methane gas, with a methane digester or, for a much wilder idea, it could
be broken down with pyrolisis. Pyrolisis was used extensively to run cars
on firewood in oil-scarce Europe and elsewhere during World War 2. The
processor has a heat source that heats the fuel (wood or glycerine) in an
airtight box without oxygen. This allows the fuel to release its methane
while not allowing it to burn. The methane is trapped in an inflatable
storage container or compressed into a tank. This is an area of biodiesel
development that warrants further work.
Suspended in the biodiesel
will also be some soapy residues. These are the result of Na+ ions from
the sodium hydroxide (NaOH) reacting with water created when the methanol
bonds with the ester chains along with any other water that was suspended
in the WVO.
If the reaction produces more than the usual amount of soap, this happens
when lye comes into contact with water before it has a chance to react
with the WVO -- in this case the excess water should have been boiled off
first. (See Step 2, above, Removing the water.)
The part of the process where it's vital to keep all water out of the
reaction is when making the sodium methoxide. Keep the blender and all
utensils the lye comes in contact with as dry as possible. The chances of
a good clean splitting of esters from glycerine with little soap
by-product are much better on a warm dry summer day than on a damp winter
Washing and drying
There is more than one
school of thought on getting the biodiesel from this stage to the fuel
tank. One is to let it sit for a while (about a week), allowing the
majority of the soap residues to settle before running the biodiesel
through a filtration system then into the vehicle/home fuel tank.
Another method is to wash the soaps out of the fuel with water, one or
more times. When washing biodiesel the first time it's best to add a small
amount of acetic acid (vinegar) before adding the water. The acetic acid
brings the pH of the solution closer to neutral because it neutralizes and
drops out any lye suspended in the biodiesel.
Figure 7 shows a simple way of washing using a translucent PVC type
container with a valve 3-4 inches from bottom. For 5 gallon batches use
those 5-7 gallon buckets found everywhere these days. If a translucent
container can't be found one fabricated with a sight tube (#6) ought to
Fill with water until it is halfway between the container's bottom and the
valve, then fill up with the biodiesel to be washed. After a gentle
stirring (keep it gentle, you don't want to agitate up soaps) followed by
12-24 hours of settling, the oil and water will separate, the cleaned oil
can be decanted out the valve, leaving the denser soapy water to be
drained out the bottom (#5).
This process might have to be repeated two or three times to remove close
to 100% of soaps. The second and third washings can be done with water
alone. After the third washing any remaining water gets removed by
re-heating the oil slowly (Figure 8), the water and other impurities sink
to bottom. The finished product should be pH 7, checked with litmus paper
or with a digital pH tester.
The water from the third wash can be used for the first or second washes
for the next batch. The impurities can be left in the re-heater for the
next batch and removed when it accumulates. The soaps can be concentrated,
left-over biodiesel can be decanted out and what's left is a biodegradable
soap good for many industrial-type uses (degreasers etc.).
I had some success with trapping the concentrated very hydrated sodium
from this soap. The way I did this was by pouring the soap onto a
stretched cheese cloth and allowing the water to run through leaving the
sodium on the cloth. This is as far as I've gone with this so far but it
seems one could press much of the water from the sodium then vacuum
dessicate this saturated sodium under dry conditions back to a usable
Transesterified and washed biodiesel will become clearer over time as any
remaining soaps drop out of the solution.
Another idea I have been working with is chilling down the biodiesel thus
allowing the soaps to condense and settle out faster. When the oil gets
chilled it seems to speed up the settling of the residual lye. With a
short settling time the oil clears considerably.
Some experimenters are
getting good results with the Idaho bubble washing technique. It takes
longer, but uses less water. They find it very effective, giving a clean,
Here's how they do it. The bubbles are formed by compressed air passing
through an air stone. For a small installation, buy an aerator at an
aquarium shop -- they come in several sizes and cost about $10 to $40.
Sometimes they have a filter attached -- throw it away.
Add about 30 milliliters of vinegar (acetic acid) per 100 liters of
biodiesel and then about 50% water. Then drop in the air stone.
The air stone sinks to the bottom of the tank. When you switch on the
aerator, the air bubbles rise through the biodiesel, carrying a film of
water which washes the biodiesel as it passes through. At the surface, the
bubble bursts, leaving a small drop of water which sinks back down through
the biodiesel, washing again.
If the mixture is still cloudy after a couple of hours, add a little more
Bubble-wash for 12 hours or longer (up to 24), then drain off the washing
water, skim off any wax floating on top. Repeat the bubble wash two more
times; keep the water from the 2nd and 3rd wash for washing the next
For severe soap formations, first heat the biodiesel/soap mixture to 122
deg F (50 deg C). Add enough vinegar to bring the pH to slightly below 7.
Stir for half an hour, cool and continue with bubble drying as usual.
The quality of the fuel
product can be checked by visually examining it and checking its pH. The
pH of the finished product can be checked with pH paper or a digital
tester. It should be neutral (pH 7). It should look like clear vegetable
oil with a light brown tint, similar to filtered apple cider.
There are not supposed to be any films, particles or cloudiness to it.
Films would be remaining soapy residue, re-wash or re-filter it at 5
micron or finer. Cloudiness would be water still in it, re-heat it.
Particles could be anything and indicates the filter is failing.
Any oils will clear up considerably when heated but the test is, when it
cools back down is it still clear? If it is not yet clear then allowing it
to settle out for an additional week or two should be enough to clear it
For final filtering it is best to use a marine-type fuel filter -- the
ones with a transparent canister so it is possible to keep an eye on the
fuel's clarity. I used to trust when I washed it to just pouring fuel into
the tank through folded cheesecloth in a funnel. After running into an
increased number of dirty fuel filters I've become more careful.
It is important to know also that biodiesel does a great job of cleaning
up fossil diesel fuel films coating the interior parts of any old diesel
engine. For this reason, take care to check and change your vehicle's fuel
filters when first switching over to biodiesel. I like putting a small,
cheap, clear or translucent plastic in-line fuel filter right before my
vehicle's stock filter. This will prefilter the fuel before it reaches the
vehicle's fuel filter, which is more expensive to replace. This also makes
it easy to see when fuel is flowing and to keep an eye on the condition of
Biodiesel does have some
limitations. First it has cold-weather starting problems. Depending on the
type of oil used, around 40 deg F (4-5 deg C) it may start to solidify.
about the weather".) One remedy is to mix with a
proportion of fossil diesel. Or try a Racor or Diesel-Therm electric fuel
heater. Heated garages are nice too. Some people report that standard
antigelling compounds work fine, others say they're unpredictable. (Be
aware that antigelling agents can be highly toxic.)
Another cold-weather idea is the two-stage method recommended by Aleks
Kac. He has found that doing the reaction this way leaves him
with a fuel that works better in colder conditions.
Retard the injection timing by 2-3 degrees -- this overcomes some of the
effect of biodiesel's higher cetane
number. The engine loses a bit of the extra power you get
with biodiesel, but it runs quieter and the fuel burns cooler, reducing
NOx emissions. (See also NOx
emissions and biodiesel.)
There can be an increased rate of corrosion of rubber parts in the fuel
system over time with 100% biodiesel. Newer cars do not use rubber parts.
Biodiesel has been used in many older motors without any problems. Viton
parts are best, but others are just as good. Check this table: "Durability
of Various Plastics: Alcohols vs. Gasoline", see Methanol.
For anyone interested in biodiesel and other renewable energy sources I
encourage you to look through the extensive Journey to Forever website.
This is a most exciting project so please spread the word about it.
Thanks go to Keith and Midori at Journey to Forever, the creators of The
Fat of The Land video, to Tom
Reed for the assistance he gladly dispensed to me when I first got
started, Aleks Kac, Terry
de Winne ("Terry UK"), Dave
Elliott ("Dave UK"), Bill Battagin, Martin
Steele, Peter Pessiki at the Evergreen State College (TESC) in
Olympia, Washington, USA, and the many interesting and generous
contributors at The Biodiesel Discussion Group and Message Board.
Have fun with it. And be safe!
For any questions or comments on how this project works out for you I can
be reached at Renewablenergies@yahoo.com.
And once you have a system up and running send pictures and how-to's to firstname.lastname@example.org
so we all can share what you have learned.