National Sustainable Agriculture Information Service
www.attra.ncat.org
Biodiesel - A Primer
FARM ENERGY TECHNICAL NOTE
Abstract: This publication is an introduction to home biodiesel production. It includes lists of equipment and materials
needed to make small batches of biodiesel. It describes biodiesel and includes cautionary notes and procedures for making
test batches and 5-gallon batches. An extensive resource list is also provided.
By David Ryan, P.E.
NCAT Energy Specialist
December 2004
©NCAT 2004
Introduction
Biodiesel is an alternative to petroleum diesel. It is called
biodiesel because it is made from mostly biodegradable
materials and can be used as fuel in diesel engines. It
can also be used in boilers or furnaces designed to use
heating oils or in oil-fueled lighting equipment. It can
be used neat (100% biodiesel), or it can be blended with
petroleum diesel.
The purpose of this publication is to describe how
biodiesel can be made by an individual to provide fuel
for diesel machinery on a farm or ranch. Please note
that biodiesel used on public roads is subject to federal,
state, and local taxes, just as is petroleum diesel. There
are several processes that can be used to make biodiesel;
this publication will describe one simple process. For information about other processes and other research done
on biodiesel, see the Resources section. Note that there
are a number of resources describing closed biodiesel
processors, including how to make them at a low cost.
A closed system processor mitigates some of the safety
issues and can save money by reclaiming methanol, an
expensive component of biodiesel.
Biodiesel can be made in any quantity, from a cup or so
up to many gallons. The process described here is a batch
process. Steady flow processes are more appropriate for
biodiesel manufacturing plants than for the individual
farmer or rancher. Since it is better to make small mistakes than big mistakes, I encourage people interested in
making biodiesel to start with small batches and gradually work up to making larger batches.
Introduction ............................. 1
Table of Contents...................... 1
About Biodiesel ........................ 3
Making a Small Batch Using New
Vegetable Oil ......................... 5
Making a Small Batch Using Waste
Vegetable Oil ......................... 6
Making a Larger Batch Using New
Oil ........................................ 7
Making a Larger Batch Using Used
Fryer Oil ............................... 8
Washing Biodiesel .................... 8
How to Use Biodiesel .............. 10
Resources .............................. 10
Table of Contents
ATTRA is the national sustainable agriculture information service operated by the National Center for Appropriate
Technology, through a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These
organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville,
Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California.
HAZARDS!
Some words of caution: Making biodiesel is relatively simple, easier than making beer.
However, there are caustic, toxic, volatile, and flammable chemicals involved. The potential
for personal injury and property damage is very real. Neither the author of this publication,
the National Center for Appropriate Technology, nor anyone else is responsible for the
mistakes you make. Do not rely solely on this publication for information about making
biodiesel; carefully study other publications and start small. Wear an appropriate respi-
rator (note that the only approved respirators for methanol are respirators with external
air supplies; see Resources), heavy rubber gloves, safety goggles, and clothing that will
protect your skin from chemicals, especially methanol. It can be absorbed through the
skin and cause illness, blindness, or debilitation.
Heating the oil to remove the water and transferring the oil to buckets are two potentially
dangerous steps in the process of making biodiesel. When heating the used oil, be careful
to keep it from spattering and making the floor slippery. You also need to be cautious
about using burners or electric heaters, just as if you were cooking. Hot oil will melt
plastic buckets, and you will have a mess. Be careful to cool hot oil to below 120°F
before pouring it into a plastic bucket. Do not use anything that comes in contact with
biodiesel or the chemicals used to make biodiesel for food production.
Making biodiesel requires a well-ventilated area to reduce the danger of fire and explosion
and exposure to methanol. Methanol can vaporize, and given the proper mix with oxygen
and an ignition source, it can ignite with invisible flame—that’s why to make it safer oil
companies had to put 15 percent gasoline in it so the flames could be seen. When mak-
ing biodiesel in larger quantities, make it outside or somewhere there is no chance of a
spark or flame coming in contact with the methanol. Any wiring in indoor areas where
methanol is used must be explosion proof.
Feedstocks
Either new or used vegetable oil (cooking oil) can
be used as a fuel for diesel engines under proper
conditions. Vegetable oil must be filtered to 5
microns and heated to at least 140°F for use in
diesel engines. See Resourcesfor more on using
waste vegetable oils for fuel.
PAGE 2
//BIODIESEL - A PRIMER
About Biodiesel
Biodiesel is made by chemically reacting vegetable oil or animal fat (or combinations of oils and
fats) with alcohol (usually nearly pure methanol
or denatured ethanol) and a catalyst (sodium
hydroxide, or lye). The oil is chemically acidic;
the alcohol is chemically a base. This chemical
reaction breaks the fat molecules in the oils into
an ester, which is the biodiesel fuel, and glycerol.
This reaction is called transesterification. Since
the biodiesel is less dense than the glycerol, it
floats on top of the glycerol and may be pumped
off, or the glycerol can be drained off the bottom.
The fuel can then be filtered and used in heating
or lighting applications. Some people use it in
diesel engines without further processing, but
others recommend removing impurities (soap,
un-reacted alcohol, and sodium hydroxide) by a
washing process.
Almost any variety of oil or grease — from new
food-grade vegetable oil to used cooking oil or
trap grease to waste water treatment-plant grease
— can be turned into biodiesel. We do not recommend using waste water treatment-plant or trap
grease for home production, because of potential
cross-contamination with hazardous materials
such as pesticides, herbicides, and toxic cleaners.
A 2001 survey showed that waste-water treatment
grease picked up a number of bad compounds
(including benzene, toluene, arsenic, and lead)
from other sources on its way to the plant. Even
trap grease from a restaurant had contamination
problems. If you have access to inexpensive oil
or grease, such as a by-product of some process,
it may be quite cost-effective for you to manufacture your own fuel from these by-products. The
amounts of reactants (oil, methanol, and sodium
hydroxide) vary to some degree, depending on
what oil you use. The amount of methanol and
sodium hydroxide must be sufficient to react with
the vegetable oil, but you should not use excessive amounts of these reactants. The cost of the
methanol and sodium hydroxide is significant,
and you do not want to waste them. Just as an
engine requires excess air to be sure that all the
fuel burns, it takes excess methanol to be sure
all of the oil reacts. As you develop your own
expertise, you will be able to adjust the amounts
used to optimize your process and minimize how
much of the reactants you use.
Anyone who has experience with diesel engines
knows that diesel fuel will turn into a waxy gel
at low temperatures and cannot be pumped until
it is warmed up. The temperature at which the
fuel will no longer pour is called the pour point or
gel point. Biodiesel has a higher pour point than
No. 2 petroleum diesel (biodiesel gels at a higher
temperature). Some oil feed-stocks, such as coconut oil or animal fats, result in biodiesel that
will gel at relatively high temperatures, whereas
biodiesel made from canola or rapeseed oil will
have a lower pour point. Additives can lower
the pour point in cold weather, or biodiesel can
be mixed with No. 1 petroleum diesel to lower
the pour point. Biodiesel should be stored at
above-freezing temperature, and temperature
controlled heaters can be installed on tanks and
fuel lines in diesel vehicles. Some vehicles have
heated fuel filters that also help.
Storage of chemicals and biodiesel
Feed stocks and finished biodiesel should be
properly stored. Methanol is a poison. You
should avoid all contact with it, including getting
it on your skin or breathing the fumes, because
contact with methanol can cause irreversible illness, blindness, and death. Methanol absorbs
water, and so should not be stored in any open
container. Methanol should be stored in appropriate sealed containers, and these should be
plainly marked as containing methanol. Sodium
hydroxide is caustic (a strong base). Sodium
hydroxide also absorbs water and will become
unusable unless it is kept in a tightly sealed
container. One step in making biodiesel is the
making of sodium methoxide. Do not mix up and
store methoxide in advance. React the methoxide
with the oil as soon as possible.
Oil feed stocks can go rancid (smell bad) or even
be rancid when you get them. Avoid rancid oils.
Used oil should be turned into biodiesel as soon as
possible, in order to keep it from going rancid and
increasing the amount of free fatty acids. Rancid
oil produces less biodiesel and may not even react
to make it. Finished biodiesel has a long shelf life.
Finished biodiesel should be stored in yellow
diesel cans, and these should be clearly marked as
containing biodiesel. Biodiesel is a good solvent.
It will dissolve rubber and some plastics, remove
paint, oxidize aluminum and other metals, and
has been reported to destroy asphalt and concrete
if spills were not cleaned quickly. Keep it off
items you care about.
// BIODIESEL - A PRIMER PAGE 3
Materials
As mentioned above, biodiesel production requires three inputs: oil or fat, alcohol, and sodium
hydroxide (caustic soda or lye). Approximately
80% percent by volume of the feed stock of
biodiesel is vegetable oil (and/or animal fats) and
about 20% is methanol. For the oil component,
you may use new, de-gummed vegetable oil or
get waste vegetable oil from restaurants. If you
are an oilseed farmer, you can press and de-gum
your own oil or get pressed raw oil. Food-service
suppliers sell new oil in 5-gallon or larger containers. Methanol, or “wood alcohol,” is made
primarily from natural gas. It is used as a gas
line antifreeze and for racing fuel. You can get
methanol from a chemical supply house, and
once you get serious about making biodiesel, you
can get methanol in 55-gallon drums from racing-fuel supply stores or auto parts stores. HEET
fuel antifreeze is 99% pure methanol and can be
used for small text batches. Do not assume that
a fuel line antifreeze is pure methanol unless it
is so labeled. You will want to use nearly pure
methanol. Sodium hydroxide in the form of Red
Devil Lye is commonly used as a drain cleaner
and is available from hardware stores and many
grocery stores.
Although you may have to pay for waste vegetable oil, as a rule you can often get it free from
restaurants. Shop around. Smaller restaurants
may let you pick up waste oil in buckets, if you
provide exchange buckets. Find out when the
fryer oil is to be changed, and pick it up warm
if you can. To get the best quality oil, talk to
the restaurant owner and, more importantly, to
the head cook, and let them know what you are
doing and what you need. If you do not make
a mess and are conscientious, most restaurant
owners will be happy to work with you. It is not
recommended that you take oil from the back of
the restaurant. First, it may have excess water
and be of poor quality. Second, you could get
arrested for theft. Check with your state and
local governments for any necessary permits,
as some jurisdictions charge fines for improper
disposal of used oils.
Cost
Besides the initial cost of the processing equipment, biodiesel production costs include the
cost of the chemicals used in the reaction, gas or
electricity expenses, and labor (your time). Feed
stocks can range from new food-grade cooking oil
($2.30 or more per gallon) to animal fat renderings. The cost of the feed stock is very specific
to your location and operation. Waste oil from
restaurants may cost as much as $0.15 per pound
(or about $1.20 per gallon), or you may be able
to get it for the cost of the replacement buckets
and your time to pick it up. Farmers who grow
oilseeds may be able to press oil at the farm for
a relatively low cost. Near pure methanol costs
about $2.36 per gallon in bulk (2004). Note: The
cost of methanol varies significantly, depending on where you get it. Almost all methanol is
manufactured from natural gas and is really an
industrial by-product. Shop around to get the
best price you can. Remember that methanol is
a hazardous chemical, and shipping costs can be
significant. Eighteen ounces of sodium hydroxide (Red Devil Lye) costs about $7.00.
PAGE 4
//BIODIESEL - A PRIMER
Small Batch v. Large Batch:
Sample Cost Comparisons
Note: These examples do not account for the
cost of equipment. The equipment needed to
make 5 gallons of biodiesel is relatively inexpensive and easy to get. The equipment to make
250 gallons of biodiesel is more involved. Also,
the examples are intended to compare the cost
of a small batch with the cost of a large batch.
Example 1: Say you go to a restaurant and get
5 gallons of waste vegetable oil from the deep
fryer, at no cost. You go to Sunoco Racing Fuels
and buy a gallon of methanol for $15.24. You
find by doing a titration (see procedure below)
that you need 3½ ounces of sodium hydroxide, costing $1.36. You end up with 5 gallons
of biodiesel and a little more than a gallon of
glycerol. The cost of the biodiesel is $3.32 per
gallon, not including appropriate road taxes.
Example 2: Say you go to a restaurant and purchase 250 gallons of used oil for $182.00. You
go to Sunoco and buy 50 gallons of methanol
for $118.00. You need 18 ounces of sodium
hydroxide at a cost of $7.00. The total cost
is $307.00. You end up with 250 gallons of
biodiesel at a cost of $1.23 per gallon, before
taxes.
Making a Small Batch Using
New Vegetable Oil
Equipment
There are several suppliers of biodiesel kits
(see Resources). Before purchasing any kit,
research the kits carefully, and be comfortable
with making small batches. Some farmers will
already have all of the equipment. For safety,
a completely closed system is best. There are
several how-to references available for making
a closed-system biodiesel reactor. This publication describes a simple open-system method to
be used by a responsible adult with proper safety
equipment.
To make a small batch of biodiesel from new oil,
you will need the following.
A blender with a glass jar. (These are available at
second-hand stores for a few dollars) or a glass
jar with a tight fitting lid to use to shake the reactants. Note: After using the blender or jar to
make biodiesel, do not use it for any food preparation. Also note that the biodiesel will dissolve
any natural rubber. The seals that come with the
second-hand blender will probably not last too
long. You can cut new seals out of Teflon sheeting available from auto parts stores.
A scale that can weigh 0 to 50 grams to the nearest
0.1 gram.
One quart jar.
One-cup liquid measuring cup (glass or plastic
compatible with methanol).
A hand pump. (Inexpensive pumps are available
at cleaning supply stores.)
Vegetable oil.
Methanol.
Sodium hydroxide (lye).
Method
Have all the materials warm, room temperature
at the coolest, 130°F at the warmest. Put on the
respirator, goggles, and gloves (See Hazards!
box). Place 1 fluid cup of methanol in the blender.
Measure out 3.5 grams of sodium hydroxide from
a new container and place it in the methanol in
the blender. Put the top on the blender and blend
on low speed for about five minutes. Shut off
the blender. The mixture in the blender is now
sodium methoxide, a strong base. Avoid getting
this on anything, especially yourself.
Measure one quart of new vegetable oil and pour
it into the sodium methoxide in the blender. Put
the lid on (you may now take off the respirator,
gloves, and goggles) and blend at low speed for
a half hour. Let the mixture settle at room temperature for at least eight hours. The mixture
is now composed of light-colored methyl esters
(biodiesel) floating on top of heavier, darker
glycerol. Using the hand pump, pump the light
biodiesel off of the glycerol.
The resulting biodiesel can be used in oil-fired
heating equipment or some oil lamps. Some people use biodiesel at this stage in diesel engines; I
// BIODIESEL - A PRIMER PAGE 5
recommend washing the biodiesel (see Washing
Biodiesel, below). The glycerol can be used to
make soap, or it can be poured into a pan, left to
dry-out for a week or so, and then put into a compost bin. Glycerol can also be burned as a fuel;
see Glycerin Uses in the Resources section.
If you were not successful, make sure you follow
the recipe exactly, and try again. Unsuccessful
batches can show up in a variety of ways, but if
you are using new oil, a batch can fail because
you didn’t use almost pure methanol, you used
old sodium hydroxide, you did not mix the solutions long enough, or the temperature was too
low. If you do not have two distinct layers in
the blender, you probably did not use enough
sodium hydroxide. If you have a solid white
material in the blender, this is soap. Study the
How-To Resources for help in figuring out what
went wrong and how an unsuccessful batch may
be remedied. Get comfortable making small
batches before moving up to a larger batch.
Making a Small Batch Using
Waste Vegetable Oil
Waste or old oil is more acidic than new oil, since
free fatty acids form in oil with use. Because
of the high content of free fatty acids, more sodium hydroxide catalyst is required for making
biodiesel from waste oil than from new oil. As
described below, when using waste oil, you will
need to perform a titration to determine how
much additional catalyst is needed.
While some resources recommend making
multiple small batches of biodiesel, varying the
quantity of sodium hydroxide until the reaction
works, titration is simple enough that, overall,
it will save you time and materials. Different
titration methods are presented in various references. One simple method is presented below,
using a chemical indicator called phenol red. This
titration method should give you an accurate
indication of the additional amount of sodium
hydroxide needed to neutralize the free fatty
acids in the waste vegetable oil. Other titration
methods are similar except for the method used
to determine when a solution that you prepare
changes from an acid to a base.
How to do a titration
Materials
One bottle of isopropyl alcohol. (In the U.S., Iso-
HEET® Premium Fuel System Dryer & Antifreeze,
12 fl. oz., in the red bottle, is available at auto
parts stores and is about 100% isopropyl alcohol.
Isopropyl alcohol is also available at pharmacies.
One bottle of phenol red from the hot tub store.
One liter of 0.1% sodium hydroxide in distilled
water—which is another way of saying 1 gram
sodium hydroxide (lye) dissolved in 1 liter of
distilled water.
Since you might not have particularly accurate
scales, one way of achieving this is to measure
out 10 grams of lye and dissolve it into 1 liter of
distilled water. Now take 100 milliliters of this
water and mix it with 900 milliliters distilled water.
You now have pretty close to the 1 gram of lye in
1 liter of distilled water. You can also go to your
local pharmacist or high school science department
and ask them to do the measuring for you.
Equipment
One one-cup jelly jar.
Two glass 1 milliliter eyedroppers with graduations
marked on the side. Note that you will use one
for oil, one for the lye-water mixture. Always use
the same eyedropper for the same chemical; do
not mix them up.
The procedure
1. Pour 10 milliliters of room-temperature isopropyl alcohol into the one-cup jelly jar.
2. Add 2 or 3 drops of phenol red to the alcohol.
3. Using one of the eyedroppers, slowly, drop by
drop, add the 0.1% lye solution until the alcohol
just starts to turn red. Stir the alcohol while dropping in the 0.1% lye solution.
(continued next page)
PAGE 6
//BIODIESEL - A PRIMER
4. Using the other eyedropper, add exactly 1 milliliter of the oil to be titrated.
5. Now, filling the eyedropper with exactly 1 milliliter of 0.1% lye solution, start dripping this solution into the medicine measure while stirring.
6. Keep track of how many milliliters of 0.1% lye
solution are needed for the liquid to turn and
stay red.
The number of milliliters of 0.1% lye solution
needed is equal to the number of extra grams of
pure sodium hydroxide catalyst needed to produce
the proper reactions to make biodiesel. For example, if it takes 3 milliliters of 0.1% lye solution
to turn the oil and isopropyl alcohol solution to
a base, you will need to add 3 grams of sodium
hydroxide to the 3.5 grams for new oil, or 6.5
grams total per liter of waste oil.
Once you have determined how much sodium
hydroxide you need by titration, make a small
batch of biodiesel in the same way you made it
with new oil, but use the total amount (new oil
plus titration result) of sodium hydroxide.
One thing you may notice in your small batch
is more than two layers. A white layer between
the biodiesel and the glycerol is soap, and it will
be present if there is any water in the waste vegetable oil or the other reactants you started with.
Warming the oil will cause the water to sink to the
bottom of the container, and the oil can be poured
or pumped off of the top. After warming the oil,
allow it to cool below 130°F, and pump the oil
into another bucket. Filter the warm oil through
a filter paper. A paper coffee filter, a funnel, and
patience will work for small batches.
If there is a layer of unreacted vegetable oil, you
didn’t use enough lye. You might make a gel
soap if you use too much lye. Study the Resources for clues to what went wrong and how
to remedy it. You can heat the oil to help get rid
of the water before reaction with the methanol. It
is best to heat the oil to a fairly low temperature
(200°F) and hold it there, rather than heating it
to a high temperature; it takes less energy and
makes fewer free fatty acids (FFAs).
If you have a good separation between the layers
of biodiesel on top and glycerol on the bottom,
pump the biodiesel off of the top into another
container, being careful not to bring any glycerol
or visible soap along with it.
Quality Testing
Soap, methanol, and lye will still be suspended
in your biodiesel. You can test for these because
they are chemical bases. The pH of unwashed
biodiesel will be above 8, and you want your
finished fuel to be pH 7, neutral. If the pH
is high, you can use less lye. If you shake up
some of the biodiesel with water and it won’t
settle out, you have soap and other impurities
in the biodiesel.
Making a Larger Batch Using
New Oil
Materials
One 7-gallon plastic bucket. You can find these at
a homebrew supply store, where you can also
get a valve that you will need to install as close
to the bottom of the 7-gallon bucket as possible.
The homebrew supply will have buckets with the
valve already installed, but it is usually placed
farther up on the bucket than you want for draining impurities. Also, the bucket must have a lid
with a hole in it for the shaft of the mixer. The
ones from the homebrew supply store have a hole
in the center, but it is usually too large. Get a new
lid and cut a small hole in it for the shaft of the
mixer. The smaller the hole the better.
Electric drill. If you are very patient, you can
stand there with the drill in your hand and mix
the reactants, but you will probably want to fabricate something to hold the drill. There are some
suggestions in the How-To Resources.
Paint stirrer that will fit in the drill.
A scale that can measure 0 to 100 grams in 0.1 gram
increments.
A drill pump and a 5-micron diesel filter.
// BIODIESEL - A PRIMER PAGE 7
Five gallons of new or de-gummed vegetable oil.
One gallon of nearly pure methanol.
Sixty-six and one-half grams (2.34 ounces) sodium
hydroxide.
Procedure
Have all the materials warm, room temperature at
the coolest, 130°F at the warmest. Put on gloves,
respirator, and goggles. In a well ventilated area
place 1 gallon of methanol in the bucket. Measure out 66.5 grams of sodium hydroxide from
a new container and place it in the methanol in
the bucket.
Put the lid on the bucket and mix with the paint
mixer for about five minutes. Remove the lid.
What is in the bucket now is sodium methoxide. Avoid getting this on anything, especially
yourself.
Measure out 5 gallons of new vegetable oil and
pour it into the sodium methoxide in the bucket.
Put the lid on (you may now take off the respirator, gloves, and goggles) and blend at low speed
for one half hour.
Let the mixture settle in a well-ventilated area
at room temperature for at least eight hours.
What you have now is light-colored methyl esters (biodiesel) floating on top of heavier, darker
glycerol. Using a small pump (a drill pump will
work for this) pump the biodiesel through the
diesel filter into another container for washing,
being careful to get just the biodiesel layer into
the wash container.
Making a Larger Batch Using
Used Fryer Oil
Used fryer oil is a little different from new oil.
Used oil probably has water and food particles in
it. Used oil also contains free fatty acids caused
by cooking with it. Remember that the titration
will give you the number of additional grams of
sodium hydroxide per liter of waste oil, so you
must multiply the number of additional grams
of sodium hydroxide by the number of liters of
waste oil you are using.
Use the same equipment as you did making a 5gallon batch with new oil. There is a handy chart
in From the Fryer to the Fuel Tank (see Web-Based
How-To Resources) for the amount of sodium
hydroxide to use for various quantities of oil and
various titration numbers.
Procedure
Perform a titration on the waste oil, to determine
how much sodium hydroxide is needed for the
reaction (in addition to the 3.5 grams per liter
of new oil). Have all the materials warm, room
temperature at the coolest, 130°F at the warmest.
To filter waste vegetable oil, warm it in a stock-
pot, and pour it through a filter paper. These
and the filter basket are available from restaurant supply stores. If the oil is very warm, let it
cool to 120°F. Filter the oil and remove water as
described above.
Follow the directions above for making a 5-gallon batch using new oil, but using the amount of
sodium hydroxide called for by the titration.
Washing Biodiesel
Unwashed biodiesel will not meet ASTM
(American Society of Testing and Materials)
standards. For more information about ASTM
standards, and testing and specifications for
biodiesel and other diesel fuels, see Resources.
Remember, equipment and engine manufacturers only warranty their equipment and engines
for their material and manufacturer defects.
Fuel manufacturers (in this case, you) assume
responsibility for any damage caused by the
fuel. Washing biodiesel is easy to do, and
requires only water and time.
Why wash biodiesel?
The biodiesel produced with the process described above will work in some heating and
lighting equipment and may be used to fuel
diesel engines. Most impurities settle out into
the glycerol layer—including unfiltered particulates, methanol, and glycerin. Some sources
encourage using unwashed biodiesel, because
washing biodiesel is a time- consuming process.
However, some alcohol, sodium hydroxide, and
soap remain suspended throughout the biodiesel
after the transesterification is complete. Water in
biodiesel can lead to biological growth as the fuel
PAGE 8
//BIODIESEL - A PRIMER
degrades. Unreacted methanol in the biodiesel
fuel can result in fire or explosion and can corrode engine components. The catalyst, sodium
hydroxide, can also attack other engine components. Since the methanol and sodium hydroxide
are chemical bases, unwashed biodiesel is caustic
and may damage diesel engine components.
Soap is not a fuel and will reduce fuel lubricity
and cause injector coking and other deposits. At
the 5-gallon batch quantity described above, it is
not feasible to reclaim the methanol. If you begin
making significant quantities of biodiesel, you
should reclaim the unreacted methanol, because
the reclaimed methanol represents a significant
cost savings, and methanol is a pollutant in its
own right.
Minimize contamination
To minimize impurities in the biodiesel, filter the
oil before you mix it with methoxide. Remove all
the water from waste vegetable oil by heating it
before it is processed into biodiesel. Do not use
any more methanol or sodium hydroxide than is
needed to have an efficient reaction.
Most of the unreacted sodium hydroxide ends
up in the glycerol layer and can be discarded
or used to make soap (see Soap Making Using
Biodiesel Waste). Most soap (if there is any
water and FFA in the oil you started with) ends
up in a white layer between the glycerol and the
biodiesel. Drain this layer off with the glycerol
before washing the biodiesel.
Remove unreacted methanol
Unreacted alcohol may be distilled from the
biodiesel and reclaimed for use in future batches
(more than one quarter of the methanol in the
recipe will end up unreacted). Although alcohol
reclamation is beyond the scope of this publication, note that methanol boils at 148°F at sea
level. Methanol can be driven from biodiesel by
heating it; do this outside or vent the methanol to
the outside. Never breathe methanol fumes. A
much better and safer solution is to use a vacuum
pump to lower the pressure of a closed tank. The
methanol can be collected and re-used. See the
Resources section on methanol reclamation.
Washing Techniques
There are three techniques for washing biodiesel:
agitation washing, mist washing, and bubble
washing. The process of washing biodiesel involves mixing it with water. Water is heavier than
biodiesel and absorbs the excess alcohol, sodium
hydroxide, and soap suspended in it. After washing and settling, the water and the impurities
in the water can be drained from the bottom of
the container. Several wash cycles are generally
needed. The first water drained off the bottom
of the biodiesel will be milky, and the final wash
water drained off will be clear. Excess sodium
hydroxide in the biodiesel will form soap when
mixed with water, and it takes a while for the
soap to settle out. Depending on the method you
use, it takes roughly as much water as biodiesel
for a wash cycle. Initial washings must involve
gentle mixing to minimize the formation of soap
that will take time to settle out. However, you
want the mixing to be thorough and for the water
to be dispersed throughout the biodiesel. Agitation washing amounts to stirring water into the
biodiesel, letting it settle, and draining it off. Mist
washing is spraying a fine mist of water over the
surface of the biodiesel. Tiny droplets of water
fall through the biodiesel and pick up impurities
on the way down. Bubble washing is done by
putting a bubbler in a layer of water beneath the
biodiesel in a container. As the bubbles rise they
are coated with water, which picks up impurities
as it travels up and then back down through the
biodiesel.
Washing a Small Batch (courtesy of “Squire
Tilly”)
This is a simple, nearly foolproof method for
washing small test batches of biodiesel, and I
have often washed a sample of biodiesel in less
than an hour using this method.
Be aware that unwashed biodiesel contains soap.
If you agitate your first few washes too vigorously, the water, soap, and biodiesel will likely
form an emulsion that may take days or weeks
to separate.
Prior to washing, let the unwashed biodiesel
settle for at least eight hours and possibly as long
as a week to get rid of as much excess sodium
hydroxide as possible.
In addition to unwashed biodiesel, you will need
water, and a container about twice the volume of
the biodiesel you are washing (you may use the
container in which you reacted the biodiesel, but
this ties up that container, so you will probably
// BIODIESEL - A PRIMER PAGE 9
want to use another container).
The three important things to remember in washing are GENTLY GENTLY GENTLY.
Washing Technique
Pour 1 liter of biodiesel into a 2-liter plastic soft
drink bottle. Gently pour about 500 milliliters of
lukewarm water into the bottle. Seal with a cap
that will not leak. GENTLY rotate bottle end for
end for about 30 seconds. After 30 seconds place
the bottle upright.
If you have been GENTLE, the water and biodiesel will separate immediately.
You will notice the water is not clear.
Wearing rubber gloves, remove the cap, and using your thumb as a valve, turn the bottle upside
down and drain the water. Drain the water into
a bucket and allow it to evaporate. Discard any
residue.
Repeat the process of adding 500 milliliters of
lukewarm water, gently shaking, and draining
off the water four or five times. Each time that
you repeat the process, you should shake the
mixture a little more vigorously and for a little
longer, until by the fifth washing you are shaking
the mixture very strongly for about a minute or
a little more.
Washed biodiesel is VERY CLOUDY, much
lighter in color than the original biodiesel, and
looks terrible. After a day or two of settling and
drying it will clear.
Washing a Larger Batch
Agitation Washing
Gently mix equal parts water and unwashed
biodiesel and let settle until clear. Repeat several
times, until the water is clear. Pump the biodiesel
off of the top of the water (or drain the water off
the bottom), dry the biodiesel for a few days in
the sun.
Bubble Washing
An air pump, hose, and air stone can be bought
from an aquarium supply store. Put the weighted
air stone in the bottom of your bucket along with
the biodiesel. Then gently add about 1/3 as much
water as you have biodiesel to wash. Start the
air pump and allow the bubbles to gently wash
the biodiesel for several hours. Drain off the
milky water, and repeat this process, letting the
air pump run longer during each washing cycle,
until the water remains clear. If the bubbles cause
foam to form, use less air. You want to start out
GENTLY. After the last water drained is clear,
dry the biodiesel (see below) and it is ready to be
used as diesel engine fuel.
Mist Washing
Purchase a misting nozzle from a pet store (these
are used to keep reptiles cool) or from a drip irrigation company and connect it to your domestic
water faucet. Turn the water on to make a fine,
gentle mist, and allow the mist to float over the
surface of the biodiesel. Keep the misting nozzle
above the biodiesel. Mist the biodiesel until you
have several gallons of milky water in the bottom
of the container, then drain it off. Repeat this
process several times, until the water you drain
off is clear. Dry the biodiesel until it is clear, and
you can use it for diesel fuel.
Drying washed biodiesel
After the biodiesel is washed, it should be dried
until it is clear. This can be done by letting the
biodiesel sit (covered) in a sunny location for a
few days, or it may be heated to about 120°F for a
few hours. Reacted, washed, and dried biodiesel
may be used in any diesel engine. It should have
a pH of close to 7, or chemically neutral, and it
should have no methanol left in it.
How to Use Biodiesel
Biodiesel can be mixed with petroleum diesel
in any proportion. To prevent gelling in cold
weather, blend your biodiesel with Number 1
petroleum diesel. Biodiesel can be mixed with
heating fuel and used in oil-fired heating equipment, and it can be used in some lamps designed
to burn kerosene. Your biodiesel’s cold weather
performance depends upon what you use for
PAGE 10
//BIODIESEL - A PRIMER
oil. Canola or rapeseed oil-based biodiesel will
have better cold weather flow characteristics than
biodiesel made from coconut oil or animal fat.
Resources
Books
Note: Unless noted, none of the biodiesel resources cited below are affiliated with NCAT and may
not be associated with any other resource cited.
Biodiesel Homebrew Guide: Everything you
need to know to make quality alternative
diesel fuel out of waste restaurant fryer oil.
Version 9—May 8, 2004. By Maria “Mark”
Alovert.
For sale on-line from
www.veggieavenger.
com/store/propaganda.shtml
Small-scale Oilseed Processing. ATTRA
Publication. 2001. By Janet Bachmann.
National Center for Appropriate
Technology, Fayetteville, AR. 21 p.
Get a free printed copy by calling 1-800-
346-9140, or download from the ATTRA
Web site:
HTML
www.attra.org/attra-pub/oilseed.html
PDF
www.attra.org/attra-pub/PDF/oilseed.pdf
Biodiesel Development: New Markets for
Conventional and Genetically Modified
Agricultural Products. 1998. By James
Duffield, Hosein Shapouri, Michael
Graboski, Robert McCormick, and Richard
Wilson. United States Department of
Agriculture Economic Research Service,
Washington, DC. 31 p.
Available for download free of charge
from
www.ers.usda.gov/publications/
aer770/ or by phone at 1-800-999-6779
(Stock Number: ERSAER770) for $25.50
+ handling.
From the Fryer to the Fuel Tank: The Complete
Guide to Using Vegetable Oil as an
Alternative Fuel. By Joshua Tickell. Tickell
Energy Consulting (TEC), PMB 223, 1350
Mahan Dr. E-4, Tallahassee, FL 32308.
Available on-line in hard copy or as an
e-book on CD.
www.joshuatickell.com/products/
publications/ or
www.Veggievan.org
Web-Based How-To Resources
www.mississippi.org/programs/energy/
Biodiesel%20Study/Eng_AspectsCh1.pdf
A general introduction to biodiesel and making
biodiesel. Read this first.
www.journeytoforever.org/biodiesel_make.
html#start
Journey to Forever is a small NGO (Non-
Government Organization) based in Japan and
involved in Third World rural development
work. There is also a lot of information about
other appropriate technologies on the Journey to
Forever Web site.
www.journeytoforever.org/biodiesel_mike.
html
Located on the Journey to Forever Web site,
Mike Pelly’s biodiesel recipe is widely accepted
as being a good method for making biodiesel.
www.woodgas.com/Unlinked/biodiesel.htm
A good description of how to make small
batches of biodiesel – for demonstrations.
www.kenneke.com/~jon/Kenneke76.pdf
Another description of how to make biodiesel.
www.eline2000.com/eline/articles/biodiesel/
biodiesel.htm
A good article on making biodiesel.
www.eline2000.com/eline/video/2003.htm
On-line videos of making biodiesel.
www.biodieselgear.com/documentation/
index.htm
A good resource list for people interested in
making biodiesel.
www.biodieselgear.com/documentation/
MistWashingBiodiesel.pdf
About mist washing biodiesel.
Other Processes (High Free-Fatty-
Acid Conversion)
www.journeytoforever.org/biodiesel_
// BIODIESEL - A PRIMER PAGE 11
aleksnew.html
This is a description of a different process to
make biodiesel.
http://biodiesel.infopop.cc/eve/ubb.x?a=tpc&
s=447609751&f=629605551&m=519609261
This is a similar acid/base process described on
an Internet discussion group web site.
Internet Discussion Groups
(Joining these groups can be helpful for problem
diagnoses.)
http://groups.yahoo.com/group/biodiesel
http://groups.yahoo.com/group/
biodieselbasics
http://wwia.org/mailman/listinfo.cgi/biofuel
The Biofuel mailing list is for anyone who is
making or has an interest in making biofuels.
All aspects of biofuels use are covered. On-farm
energy is often discussed.
Web Resources
National Biodiesel Board
www.biodiesel.org
DOE Alternative Fuels Data Center
www.afdc.doe.gov/altfuel/biodiesel.html
University of Idaho
www.uidaho.edu/bae/biodiesel/
DOE Office of Transportation Technologies
www.ott.doe.gov/
DOE Energy Efficiency and Renewable Energy
Network
www.eren.doe.gov/RE/bio_fuels.html
Veggie Van Home Page
www.veggievan.org/biodiesel/
Berkeley Biodiesel Collective
http://bapd.org/gbeeve-1.html
Pacific Biodiesel, Inc.
www.biodiesel.com
Sustainable Solutions Caravan
www.sustainablesolutionscaravan.org/
englishIndex.html
National Biodiesel Board
www.biodiesel.org
Government Agencies with Biofuels
Information
Oak Ridge National Laboratories
www.esd.ornl.gov/bfdp or bioenergy.ornl.gov/
National Renewable Energy Laboratory
www.afdc.nrel.gov
Department of Energy
www.eren.doe.gov or
www.eere.energy.gov/
biomass/renewable_diesel.html
Chemistry of Biodiesel Resources
http://koal2.cop.fi/leonardo/
An interesting page about vegetable oil
transesterification and other vegetable
oil chemistry.
Standards and Testing, Chemical Composition
of Biodiesel
National Standards for Biodiesel
www.journeytoforever.org/biodiesel_yield2.
html#biodstds
Biodiesel Chemical Properties
www.chanco.unima.mw/physics/biodieselanaly.
html
ASTM Standards
www.astm.org/cgibin/SoftCart.exe/
DATABASE.CART/REDLINE_PAGES/
D6751.htm?L+mystore+dlra2970+1083877590
Cetane Number Testing of Biodiesel
www.biodiesel.org/resources/reportsdatabase/
reports/gen/19960901_gen-187.pdf
Methanol Composition and MSDS
www.bu.edu/es/labsafety/ESMSDSs/
MSMethanol.html
Glycerine Uses
www.journeytoforever.org/biodiesel_glycerin.
html
Research Sites and Papers
www.me.iastate.edu/biodiesel/
www.uidaho.edu/bae/biodiesel/
Other general information
www.allpar.com/ed/biodiesel.html
www.veggieavenger.com
PAGE 12
//BIODIESEL - A PRIMER
Using Vegetable Oils for Fuel
Using vegetable oil in diesel engines
www.oilpress.com/drive_your_diesel.htm
Using vegetable oil in diesel engines
www.rerorust.de/
Using vegetable oil in diesel engines,
conversion kits
www.biofuels.ca/
Conversion Kits
www.greasel.com/
www.greasecar.com/
Economic Feasibility of Producing Biodiesel in
Tennessee
web.utk.edu/~aimag/pubs/biodiesel.pdf
Reclaiming Methanol
www.home.swbell.net/scrof/Biod_Proc.html
www.journeytoforever.org/biodiesel_
processor2.html
www.journeytoforever.org/biodiesel_
processor8.html#press
Respirator Selection
www.cdc.gov/niosh/npg/npgd0397.html
Soap Making Using Biodiesel Waste
www.eline2000.com/eline/articles/barsoap/
barsoap.htm
www.journeytoforever.org/biodiesel_glycerin.
html#soap
www.eline2000.com/eline/video/2003.htm
Biodiesel as a Home Heating Fuel
www.biodiesel.org/markets/hom/default.asp
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FAQ
,but would it be possible to recycle the local chippy's oil 
