Technical Answers: A Sample of
Questions Directed to the
University of
Idaho Biodiesel Education Project
1.
How much
canola oil can be squeezed out of canola seeds?
Canola
seed, depending on the variety and the growing conditions,
contains about 40% oil. Therefore from one ton you should get
2000 lbs *0.4 = 800 pounds of oil. However, we generally
extract only about 80% with a mechanical press so 800 lbs *0.8 =
640 pounds of oil with the remainder in the meal. Large
commercial plants using solvent extraction can take out almost
all of the oil. Raw rapeseed oil weighs about 7.6 pounds per
gallon so the 800 lbs of oil in the seeds provides about 105
gallons of oil. Since 2000 lbs is a common yield for canola in
the Pacific Northwest, we use the figure of 100 gallons/acre as
a typical oil yield. Another general rule is that 100 gallons
of oil will produce 100 gallons of biodiesel.
2.
How
much bio-diesel is produced from 1 liter of unused vegetable oil
and how much ethanol (or wood-based methanol) is required to
make this amount of bio-diesel?
( 3.79 liters equals 1 gal )
A general recipe
for biodiesel production is: 100 grams canola, 31 grams ethanol,
and 1.4 grams potassium hydroxide (KOH). With methanol we use 22
grams with 1 gram of KOH. If the oil has been used for frying
and the free fatty acids are high it requires more catalyst to
compensate for the catalyst that will be lost to soap
formation. You need to measure the free fatty acid content of
the oil (by titrating with potassium hydroxide). Then, add 0.2
grams of extra KOH for each gram of fatty acids in the oil.
This approach will work for oils with fatty acids as high as
5-7% if the water content is low. These recipes are based on a
100% excess of alcohol so about 50% of the alcohol could be
recovered and reused if proper equipment is in place. So, since
a liter of oil weighs about 910 grams (2 lbs), you need 282
grams of ethanol and 12.7 grams of KOH.
3.
I made a
batch of biodiesel from used frying oil. After the reaction,
when I heated the fuel to drive off the excess alcohol, I found
that a translucent slime was formed. What is happening?
If your feedstock contains excessive free fatty acids and/or
water, there may be a considerable amount of soap formed during
the transesterification reaction. This soap is generally not
visible and the reaction may appear to have proceeded without
any problems. When you separate the biodiesel phase from the
glycerol phase, the excess alcohol from the reaction splits
between the two phases. The alcohol in the biodiesel phase acts
as a co-solvent to keep the soap in solution. When you drive
off the methanol, if the soap level is excessive, you will see
the soap come out of solution as a thick, viscous material. It
has been compared to the “skin” that forms on the surface of a
paint can when the lid is left off. You can confirm that this
is mostly soap by taking a sample of the material and putting it
in a small amount of water and shaking it. If it is soap, it
will dissolve into a milky mixture and form suds. This soap
material can plug filters and screens and prevent the fuel from
meeting ASTM standards. The best way to prevent this problem is
to prevent the formation of excessive soap by removing water
from the feedstock (preferably to less than 0.1%) and
pre-treating free fatty acids (so they are less than 0.5%). If
this is still a problem, then a soap-splitting process should be
inserted before the alcohol removal step. This involves adding
an acid, such as HCl, to lower the pH of the biodiesel to 4.5 to
5.0. This will cause the soap to split into free fatty acids
and salt (NaCl). The FFAs will stay with the biodiesel and the
salt will be removed during the water washing step.
4.
Will 100%
biodiesel work without any consequences for the engine other
than cold weather viscosity problems?
In general,
yes. Of course your engine must be a diesel and not
gasoline-fueled. Modern diesel engines can run on any amount of
biodiesel between 0 and 100% and you can change back and forth
depending on the availability of either fuel. We run our
vehicles on 100% biodiesel and the oldest is a 1994 Dodge with
over 135,000 miles. Keep in mind that in cold weather biodiesel
will gel at temperatures that are about 10-20ºF higher than for
diesel fuel. Work with your fuel supplier to be sure that you
get biodiesel made from feedstocks with low levels of saturated
fat, such as canola or mustard, to get the best operability at
low temperatures. Additives are also available that lower the
operating temperature of the engine (See our TechNote on Cold
Flow Additives)
5.
I pumped
the last bit of biodiesel from my storage barrel and I noticed
that the fuel contained a large number of small white flakes.
The temperature was in the 80’s, so I would not expect that the
fuel was starting to gel. What are these flakes?
These flakes are
sometimes confused with soap but this is unlikely because when
soap separates, it usually forms slime. The flakes are most
likely small particles of saturated monoglycerides, specifically
monopalmitin and monostearin. These two compounds have low
solubility in biodiesel and have very high melting points. The
presence of these flakes is a good indication that the fuel
probably does not meet ASTM specifications for total glycerin.
In most cases, if the concentration of monopalmitin and
monostearin are high enough that flakes can be observed, the
total glycerol, which is supposed to be below 0.24%, will be
above the specification value. This problem is particularly
acute when using more saturated feedstocks such as animal fats
and hydrogenated cooking oils. After cold weather problems, the
most commonly observed operational problem with biodiesel is
fuel filter plugging. When the filters are cut open, a creamy
material can be removed that is usually high in these saturated
monoglycerides.
6.
How do
biodiesel’s miles per gallon compare to the miles per gallon
(mpg) of regular diesel?
It will drop
about 8 percent with 100% biodiesel. The reduction will be less
with the blends in more or less proportion to the percentage of
biodiesel. Biodiesel has 12 percent less energy per pound but
since it has a higher density than diesel fuel, it has 8 percent
less energy per gallon. We should expect the combination of
reduced power and increased fuel consumption to be approximately
that level. Many people report that they do not see a
difference with B20 but their tests are not usually very
precise.
7.
Can I
make biodiesel on a small scale?
You can make
biodiesel on a small scale. However, it is difficult to be able
to show that it meets the ASTM specification because of the cost
of the tests. Also, on a small scale the labor cost becomes a
large part of the production cost which is okay if you think
labor is free, but very expensive if you include a reasonable
cost for your time. You also need to work out in advance what
you are going to do with your waste products including glycerin
that is contaminated with methanol and the methanol that you may
recover from the process. Improper disposal of these materials
may defeat any environmental benefits that accrue from using the
biodiesel. Be sure to study the Material Safety Data Sheets for
the methanol and catalyst and follow the safety precautions.
8.
Do I have
to register my fuel with the EPA for private and non-commercial
use? EPA
registration is only required if you intend to sell your fuel.
However, you will need to pay road taxes. You need to check with
your state fuel tax authority who can also point you in the
correct direction for federal tax. State + federal taxes are
$0.494 in Idaho.
9.
If I want
to set up a small facility and sell biodiesel can I do this?
What are the testing requirements and procedures? Does every
batch have to be tested? Do I have to be a member of NBB
(paying the $5,000 yearly membership fee)? Or can I just meet
ASTM standards? Does my fuel have to be registered with the
EPA?
To sell fuel you
must be registered with the EPA. This registration requires
that you submit data for the health effects of your product.
The National Biodiesel Board has collected these data and makes
them available as a free benefit of membership. Meeting the ASTM
spec is what the vehicle manufacturers require in order for the
fuel to be used with their engines. By the way, most
manufacturers recommend 5% biodiesel or less. One needs to be
sure that every batch meets the ASTM specifications but not
every characteristic is batch specific. The biggest issues with
the ASTM spec are free and total glycerol, acid value, water and
particulate matter. As long as the feedstock is consistent,
most of the other characteristics will not change. The EPA and
ASTM do not test fuel but your customer may require a
certificate of analysis which can be obtained from a private
laboratory.
10.
An
organization near me is producing biodiesel and I have learned
that one of the by- products from this process is glycerine, aka
glycerin glycerol (C3H8O3) – could you confirm for me that this
is what the by-product really is (from processing canola or some
such material) and whether it is a suitable co-digestive in an
agricultural anaerobic digestion process? And approximately what
volume of glycerine is generated from the production of how much
biodiesel?
Glycerol
is the fourth constituent of the reaction, 3 long chain methyl
esters and glycerol. It is about 10% the weight of the
biodiesel. It has been used in composting. Some people add it
to waste oil and burn it in boilers. It is a constituent of
many food and chemical products including explosives and
cosmetics. It appears to have no market unless it is purified
to 99.5% pure. Purification requires an expensive vacuum
distillation system or ion exchange equipment. There is a very
large market in the U.S. for glycerol but the influx of
biodiesel- based glycerine is expected to depress the market
price.
11.
Can
I use biodiesel in my 1984 Mercedes TD300?
In
1994 and again in 1996 we had Mr. Ansgar Schaefer from Mercedes
Benz, Stuttgart, Germany attend our biodiesel conferences. At
that time he indicated that some Mercedes diesel vehicles
operated better with biodiesel than others. He suggested that
trucks with 300 and 400 series "can be fueled with RME (rapeseed
methyl ester)". Leak lines of injection nozzles of series 400
engines have to be replaced with an RME-resistant version.
There is a risk that hoses and seals on older engines might be
attacked by RME and become leaky. Commercial vehicles with
series 600 engines could not be operated with RME. He did not
say why in the written paper. He also warned against RME of
inferior quality. You might ask your dealer if MB has issued a
statement for your vehicle using biodiesel.
12.
We have a
client who got an interesting test result back on some of their
biodiesel. The copper corrosion test came back as 1A, the ASTM
method specifies max of 3. Any idea what that means?
1A
is the highest possible score. This means no evidence of
tarnish or corrosion. A score of 3 means there is significant
tarnish but no corrosion. We have never seen a sample of
biodiesel get anything but the highest score on this test.
13.
Can you
provide any technical information on use of fish oil as a
feedstock? My neighbor and I tried to use it and the reaction
didn't seem to work as no separation occurred as is usual with
vegetable oil. Also, I have read press articles that seem to
say that fish oil can be used blended straight with regular
diesel to run and engine? Is this true? We are interested in
fish oil as a feedstock due to a theory that it will have much
better cold flow properties. Thank you for your help.
Usually the value of the fish oil is too high for it to be used
for biodiesel. It has been proposed for use as a fuel in
certain isolated areas where it is not economical to transport
the oil and diesel fuel is expensive. We don't recommend using
straight fish oil for the same reasons as straight vegetable
oil. There is the potential for in-cylinder deposit formation
that can be harmful to the engine. It should be possible to
make biodiesel from fish oil. This assumes the oil is clean and
free of water and free fatty acids. Did you measure the free
fatty acid level and make sure there was no water? Excessive
soap formation caused by excessive free fatty acids and water is
the most common cause of not getting a glycerin separation.
14.
Can I
change from diesel fuel to biodiesel without any physical
problems or damage to my engine if I have a 20 year old vehicle?
Diesel
engines that are 20 years old may have a problem changing over
to 100% biodiesel because of the flexible parts of the fuel
supply system, i.e. hoses, seals, and gaskets. On some older
engines these “rubber” parts may not be compatible with
biodiesel. Newer engines are almost all okay. Be aware that in
switching an old engine to 100% biodiesel you will go through a
period of fuel system “clean-out” where the biodiesel will
dissolve some of the old varnish deposits that have
accumulated. A fuel filter change after the first one or two
tanks of fuel should prevent any problems.
15.
Does
biodiesel reduce engine wear?
There are no
definitive test data showing that biodiesel reduces engine
wear. It should be noted that biodiesel only contacts the fuel
system and the upper cylinder of the engine. We would not
expect biodiesel to have any impact on bearing wear, oil or
water pump life, or many of the other wear items in the engine.
It should also be noted that diesel engines are designed to have
extremely long lives, so when properly maintained their wear
rates are very low. However, we know that biodiesel
dramatically improves fuel lubricity and that lubricity is a
necessary property for fuel system life. If the engine were
fueled with a low-lubricity fuel, typical of modern low-sulfur
fuels, that has not been treated with any lubricity-enhancing
additive; the engine’s life will be dramatically shortened.
Biodiesel can prevent this from happening.
16.
What is
the shelf life for biodiesel?
Both
petroleum-based diesel fuel and biodiesel should be treated with
a stabilizing additive if they are to be stored for more than 6
months. A popular stabilizer for biodiesel is Tenox 21,
produced by the Eastman Company. It is a mixture of Tertiary
Butyl Hydroquinone (TBHQ) and citric acid.
17.
Is there a recommended percentage of biodiesel to use with
diesel fuel? The Engine
Manufacturer’s Association has recommended that biodiesel be
limited to 5%. Many individual engine manufacturers have
now said that they are comfortable with B20. The biodiesel
industry in the United States has been actively promoting
B20 as the blend level which gives significant emissions
benefits while keeping the cost impact low. This thinking
may need to be adjusted with current government incentives
that allow biodiesel to be sold at or below the price of
conventional diesel fuel. Higher blends, such as are
currently used in Europe, should become more common.
18.
Will biodiesel void the warranty on my car?
Engine manufacturer’s warranties cover the parts and
assembly of your engine. They do not cover fuel-related
problems, regardless of whether the fuel is diesel fuel or
biodiesel. We have heard reports that some dealers have
said that using biodiesel will void your warranty but this
is not true. The important question is whether your
biodiesel supplier will stand behind his/her product and
whether they will cover any damage that might be associated
with their product. If not, then take your business
elsewhere.
19.
Can algae grow in biodiesel?
There are many microbes, including algae and fungi that will
use hydrocarbons as a food source. This is a common problem
with petroleum-based fuels and has been noted with
biodiesel, as well.. In order to grow, the microbes need
water. The solubility of water in diesel fuel is very low,
so if water is present it settles as a layer at the bottom
of the fuel tank. The microbes tend to grow at the
interface between the water and the fuel. The best way to
control the growth of the microbes is to eliminate the water
by draining the fuel tanks frequently and using desiccants
on the vent lines. Chemical biocides can be used to prevent
the growth of the microbes and at higher concentrations can
be used to kill existing infestations. However, the
preferred solution is to implement good house-keeping
practices that will prevent water from collecting at the
bottom of the fuel tank.
20.
How should biodiesel and diesel
fuel be blended?
Most biodiesel and diesel fuel are
“splash-blended.” This means they are simply pumped into
the same tank and then it is assumed that the action of the
fuels entering the tank or the motion of the transport truck
provide enough agitation to mix them together. In most
cases this is a good assumption. When making blends such as
B20, if the mixing is not perfect, there is generally no
harm since the engine will run fine on a higher or lower
blend. When using a small amount of biodiesel, such as 2%,
as a lubricity additive, then good mixing is important to be
sure the additive is providing protection for each gallon of
fuel used. In this case, more active agitation is warranted
or the biodiesel can be injected directly into the diesel
fuel stream as it fills the tank. Problems have been noted
when biodiesel has been mixed with very cold diesel fuel.
When the diesel fuel temperature is below the gel point of
the biodiesel, the biodiesel may solidify before it has a
chance to mix with the diesel fuel and fall to the bottom of
the tank. The biodiesel needs to be heated and returned to
the liquid state before it can be mixed with the diesel
fuel. In all instances, the biodiesel should be added
either at the same time as the diesel fuel or on top of the
diesel fuel. When added on top, the higher density of the
biodiesel encourages mixing as it falls through the lighter
diesel fuel.
21. Can biodiesel be
made using ethanol? Yes,
ethanol-based biodiesel, or ethyl esters, produce biodiesel
with some properties, such as gel point temperature, that
are superior to methyl esters. Ethanol also has the
advantage that it is less toxic and safer to work with.
Currently, the per gallon price for ethanol is about the
same as for methanol. However, due to its higher molecular
weight, the reaction requires about 45% more pounds of
ethanol than for methanol. The advantage is that these
extra pounds of ethanol go directly into additional
biodiesel, so the value of the biodiesel can offset the
additional cost of the ethanol. A disadvantage of using
ethanol is that when the excess ethanol is recovered
following the transesterification reaction, the alcohol will
have collected any water that was present in the reaction.
This water needs to be removed before the alcohol is reused
and since ethanol forms an azeotrope with water, the removal
process is more complicated than for methanol.
22. Can you supply
me with plans for a biodiesel plant?
We do not design or build biodiesel plants.
There are many commercial technology providers who provide
this service. Our suggestion is that you contact several
companies and check references carefully. Ask if the
company has built any plants and whether you can tour one of
their facilities. If you decide to go with a new company or
new technology, you should expect to receive a substantial
discount for helping them to develop their process.
Answers furnished by
University of Idaho Biodiesel Team: Dr.s' Jon Van Gerpen, Brian
He, Charles Peterson, Dev Shrestha, and Joe Thompson.