In a previous article on how much land is needed to grow so much food a list of oils was included but olive oil was not on the list. So we inquired on similar information and found this other article of useful information but the units are not similar. As we have some knowledge of physics this is not a problem. A Kg is equal to 1000g and a hectare is 10000sq.m. so you can divide by 100 to get your figure in Kg.100sq.m of the previous article.
We thank the editor of journeytoforever.com but as we do not believe in ownership but in sharing we will not bother with copyrights or do we consider reproduction of good information as theft, except if it was used for profit from it. This is definitely nowhere close to any of our intents or goals, quite the opposite, to help create a world as far away as possible from profit, ownership, theft, social control, and exploitation.
Enjoy the information while it lasts free and accessible. Create hardcopies and manuals of what you believe may be of use for you and your community, use responsibly. This is our tool to autonomy and freedom.
The knowledge of land and our environment and how we can collectively survive with the least possible impact. There is a lot to learn and limited time to summarize effectively. Deviate from the norm of learning what they need you to learn so they can more effectively exploit you and use within their system. Create your own system!
Do not be fouled, they will take our tools and free information away from us as soon as they realize what we are using it for. We need to defend it and share it collectively utilizing our own means.
Other oil crops Oils and esters characteristics Iodine Values -- High Iodine Values -- Talking about the weather -- Summary Hydrogenated oil, shortening, margarine Quality standard for rapeseed oil fuel Cetane Numbers National standards for biodiesel -- standards and the homebrewer -- standard testing Fuel properties of fats and oils Fuel properties of esters Fats and oils -- resources
We thank the editor of journeytoforever.com but as we do not believe in ownership but in sharing we will not bother with copyrights or do we consider reproduction of good information as theft, except if it was used for profit from it. This is definitely nowhere close to any of our intents or goals, quite the opposite, to help create a world as far away as possible from profit, ownership, theft, social control, and exploitation.
Enjoy the information while it lasts free and accessible. Create hardcopies and manuals of what you believe may be of use for you and your community, use responsibly. This is our tool to autonomy and freedom.
The knowledge of land and our environment and how we can collectively survive with the least possible impact. There is a lot to learn and limited time to summarize effectively. Deviate from the norm of learning what they need you to learn so they can more effectively exploit you and use within their system. Create your own system!
Do not be fouled, they will take our tools and free information away from us as soon as they realize what we are using it for. We need to defend it and share it collectively utilizing our own means.
Oil yields and characteristics
Vegetable oil yields Oil from algaeOther oil crops Oils and esters characteristics Iodine Values -- High Iodine Values -- Talking about the weather -- Summary Hydrogenated oil, shortening, margarine Quality standard for rapeseed oil fuel Cetane Numbers National standards for biodiesel -- standards and the homebrewer -- standard testing Fuel properties of fats and oils Fuel properties of esters Fats and oils -- resources
Vegetable oil yields
| corn (maize) | avocado | ||||
| cashew nut | brazil nut | ||||
| oats | calendula | ||||
| lupine | camelina | ||||
| kenaf | cashew nut | ||||
| calendula | castor bean | ||||
| cotton | cocoa (cacao) | ||||
| hemp | coconut | ||||
| soybean | coffee | ||||
| coffee | coriander | ||||
| linseed (flax) | corn (maize) | ||||
| hazelnut | cotton | ||||
| euphorbia | euphorbia | ||||
| pumpkin seed | hazelnut | ||||
| coriander | hemp | ||||
| mustard seed | jatropha | ||||
| camelina | jojoba | ||||
| sesame | kenaf | ||||
| safflower | linseed (flax) | ||||
| rice | lupine | ||||
| tung oil | macadamia nut | ||||
| sunflower | mustard seed | ||||
| cocoa (cacao) | oats | ||||
| peanut | oil palm | ||||
| opium poppy | olive | ||||
| rapeseed | opium poppy | ||||
| olive | peanut | ||||
| castor bean | pecan nut | ||||
| pecan nut | pumpkin seed | ||||
| jojoba | rapeseed | ||||
| jatropha | rice | ||||
| macadamia nut | safflower | ||||
| brazil nut | sesame | ||||
| avocado | soybean | ||||
| coconut | sunflower | ||||
| oil palm | tung oil | ||||
Note: These are conservative estimates -- crop yields vary widely. This data is compiled from a variety of sources. Where
sources vary averages are given. The yield figures are most useful as
comparative estimates: a high-yielding crop may not be "better" (more
suitable) than a lower-yielding crop, it depends on the particular
situation. -- Keith Addison, Handmade Projects, 2001.
High yield is not the only factor in farming, maybe not even the most important factor. See: How much fuel can we grow? How much land will it take?
Copra 62 kg
Cotton Seed 13 kg
Groundnut Kernel 42 kg
Mustard 35 kg
Palm Kernal 36 kg
Palm Fruit 20 kg
Rapeseed 37 kg
Sesame 50 kg
Soyabean 14 kg
Sunflower 32 kg
Oil from algae
Algae yield is not included in the yield tables because, in spite of all the hype about yields of 20,000 gallons of oil per acre and even 100,000 gallons per acre and so on, biodiesel from algae is still something of the future, not of the present.
As of end-2011, there is no such thing as biodiesel from algae apart from a few laboratory samples. There are some hopeful signs, but technical obstacles remain, pilot projects are not yet feasible for production purposes, and the claims made for high yields have never been demonstrated and remain theoretical.
No doubt that will change, but it's been "just around the corner" for years. When it does emerge, it's very likely to be in the form of high-tech industrial-scale solutions, not for backyarders or farms or villages.
We're sad to be so negative about it, but there's a lot of confusion about biodiesel from algae.
Of course we encourage further research. We supported many early small-scale attempts to make biodiesel from algae, but none succeeded, because of multiple problems.
The Oil_from_algae online discussion group has been working for the last seven years exclusively on biodiesel from algae production and now has more than 2,000 members, but they have no ready solution as yet: "We do not know enough yet to write you an instruction book, please help us learn," writes the group leader. Strength to their arms, we hope they have a breakthrough soon. http://tech.groups.yahoo.com/group/oil_from_algae/
Yet many people believe that making biodiesel from algae is an existing option for them now, a tried-and-trusted, ready-to-use technology.
We often receive enquiries asking why our website doesn't provide full instructions and plans for making biodiesel from algae. The answer is that we provide information you can use, and there isn't any information you can use on making biodiesel from algae, it doesn't yet exist.
Oil or biodiesel from algae is not a do-able option, there are no tried-and-trusted methods, it is not a ready-to-use technology.
But that's not the impression you get from the large amount of sheer hype flying around about algal biodiesel.
Dr John Benemann, the scientist who literally wrote the book on biodiesel from algae, has called some of the claims being made for the technology and yields "bizarre" and "totally absurd". In a critique of algal biodiesel developments in May 2007, Dr Benemann wrote:
The ASP was the U.S. Dept of Energy Aquatic Species Program, which ran for 18 years and cost $100 million.
Dr Benemann was the Principal Investigator and the main author of the ASP Close-Out Report, the book that sparked all the interest in biodiesel from algae: "A Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae", by John Benemann, John Sheehan, Terri Dunahay, Paul Roessler, July 1998, National Renewable Energy Laboratory, U.S. Department of Energy, 328 p, 3.5Mb pdf: http://www.nrel.gov/docs/legosti/fy98/24190.pdf
The Brussels-based biofuels and bioenergy network Biopact published a detailed 13,000-word critique of algal biofuels developments in January 2007, "An in-depth look at biofuels from algae", in order to "temper some of the unfounded and unsubstantiated enthusiasm surrounding algae".
The Biopact report says:
http://news.mongabay.com/bioenergy/2007/01/in-depth-look-at-biofuels-from-algae.html
Dr. Krassen Dimitrov of the Australian Institute for Bioengineering and Nanotechnology (AIBN, University of Queensland), who made an in-depth analysis of algae-to-biofuel concepts, concludes that a biodiesel-from-algae plant using the much-hyped industrial photobioreactor approach and operating at maximum efficiency is not economically feasible at fuel prices below US$800 per barrel.
"Hype surrounding some alternative energy startups sometimes disregards the laws of physics and other fundamental principles," he says.
See Scientist skeptical of algae-to-biofuels potential, Biopact, July 18, 2007:
http://news.mongabay.com/bioenergy/2007/07/scientist-skeptical-of-algae-to.html
Hope springs eternal, but don't hold your breath.
http://www.hort.purdue.edu/newcrop/SearchEngine.html
Plants For A Future -- Database Search -- See "Search by Use - Select any of the following uses. Or select none and use the plant criteria below." Select "Other Use" - oil. Results: "Other Use: Oil (460)". Results are hyperlinked to detailed factsheets.
http://www.ibiblio.org/pfaf/D_search.html
Liberty Vegetable Oil Company lists the fatty acid composition of their oils as well as other details such as the Iodine Value, SG, Flash point etc -- Sweet Almond Oil, Pecan Oil, English Walnut Oil, Hazelnut Oil, Macadamia Nut Oil, Soybean Oil, Oleic Sunflower Oil, Canola Oil, Peanut Oil, Sunflower Oil, Corn Oil, Safflower Oil, Soybean Oil (Non-GMO), High Oleic Oils including Canola and Safflower. http://www.libertyvegetableoil.com/products.html
Chemically, vegetable and animal oils and fats are triglycerides, glycerol bound to three fatty acids. Animal fat such as tallow or lard is saturated, meaning that in the fatty acid portion, all the carbon atoms are bound to two hydrogen atoms, and there are no double bonds. This allows the chains of fatty acids to be straighter and more pliable so they harden at higher temperatures (that's why lard is a solid).
As you increase the number of double bonds in a fatty acid, you reduce that ability for oils to gain a conformation that would make them solid, so they remain liquid. To picture it, imagine that you put a bunch of strings in a line. Now tie knots in various places on the strings and see how they don't fit together tightly.
To test a vegetable oil to see how many double bonds it has (how unsaturated it is) iodine is introduced to the oil. The iodine will attach itself over a double bond to make a single bond where an iodine atom is now attached to each carbon atom in that double bond. Higher iodine numbers do not refer to the amount of iodine in the oil, but rather the amount of iodine needed to "saturate" the oil, or break all the double bonds. Oils for the most part contain only trace amounts of iodine naturally.
How does this translate to biodiesel? When the fatty acid chains are broken from the glycerol and then re-esterified to methyl or ethyl groups, those fatty acids still have their double bonds. That means that the more double bonds, the lower the cloud point because they resist solidifying at lower temperatures. So, for instance, if you use lard or tallow, the biodiesel will solidify at a higher temperature because the fat it was formed from also solidified at a higher temperature.
(Image and text compliments of Jeff Welter)
The information below refers to straight vegetable oil fuel, but is also useful to show which oils are suitable for making biodiesel and which may not be suitable.
-- From "Waste Vegetable Oil as a Diesel Replacement Fuel" by Phillip Calais, Environmental Science, Murdoch University, Perth, Australia, and A.R. (Tony) Clark, Western Australian Renewable Fuels Association Inc.
http://www.shortcircuit.com.au/warfa/paper/paper.htm
Note: More Iodine Values here.
As vegetable oils cool, wax crystals form, and the oil goes cloudy. The crystals can form a film on filters, blocking the flow of fuel. The temperature at which this occurs varies widely according to the oil type, from well below freezing point to well above freezing point.
It even varies for the same type of oil: new food-grade rapeseed or canola oil is usually "winterized" so that it doesn't cloud in the fridge and put people off. It will work nicely down to -10ºC, but once it emerges from the fryer, partly hydrogenated, degraded and probably containing some tallow from the food fried in it, it will only stay liquid and not plug filters down to freezing point or just above.
If you want to use an SVO system in a cold climate, you need a system configured to deal with the CFPP factor, and you need oil with a low CFPP. Coconut oil, palm oil, tallow and lard won't do, rapeseed or canola, corn or cottonseed are much better. (Peanut oil is an exception -- see Which oil is best?)
But if you live in a hot climate, cloud points won't bother you and the opposite is true: coconut and palm oil, tallow and lard all have higher cetane numbers than the others, and lower Iodine Values.
For biodiesel, the same applies, but to a lesser degree -- with most oils and fats, converting it into biodiesel tends to lower the CFPP. Biodiesel made with ethanol usually has a lower CFPP than biodiesel made with methanol. Additives and fuel-line heaters can solve the problem, and so can adding a proportion of petro-diesel or kerosene (up to 30% is usually recommended).
See: Biodiesel in winter
The fatty acids can be saturated or unsaturated. Unsaturated fatty acids have carbon-to-carbon double bonds. In saturated fatty acids all the carbon atoms are linked to two hydrogen atoms and there are no double bonds.
The degree of saturation is indicated by the Iodine Value of the oil (IV). Low-IV oils are more saturated with fewer double-bonds (lard, tallow, palm oil, coconot oil). High-IV oils are more unsaturated with more double-bonds (linseed oil, tung oil, some fish oils and other "drying oils").
Low-IV oils have higher cetane values and are more efficient fuels than high-IV oils, but they also have higher melting points and are usually solid at room-temperature. Biodiesel made from low-IV oils also has a higher melting point and might only be suitable for use as summer fuel.
High-IV oils have lower melting points and make better cold-weather biodiesel, but with high-IV oils there is more risk of the biodiesel oxidising and polymerising (drying) into a tough, insoluble plastic-like solid. Biodiesel made from high-IV oils should be stored carefully and used quickly.
"Semi-drying" oils like soy and sunflower are also prone to oxidation and polymerisation, though not as quickly as the drying oils.
See also Oxidation and polymerisation
Storing biodiesel
Hydrogenated oils and shortening can be used to make biodiesel.
Margarine is more problematic and should be avoided, unless you're an
expert.
When oils are hydrogenated hydrogen atoms are added to the carbon-to-carbon double bonds in unsaturated fatty acids, which then become saturated. This results in higher melting points. Fully hydrogenated oil is solid at room temperature, partly hydrogenated oils range from liquid to creamy to solid.
Hydrogenation also lowers the Iodine Value (IV) of the oil. "The typical IV for unhydrogenated soybean oil is 125-140, for foodservice salad and cooking oils made from partially hydrogenated soybean oil it is 105-120, for semi-solid household shortenings made from partially hydrogenated soybean oil it is 90-95." (Institute of Shortening and Edible Oils.)
So biodiesel made from hydrogenated oil is less likely to oxidise and polymerise but will have a higher melting point than if it were made from unhydrogenated oil of the same kind. It increases the risk of filters plugging in cold weather or even just cool weather and is best used as summer fuel.
In processing, treat hydrogenated oil the same as ordinary oil. The more solid it is when you get it the more difficult it is to handle, but once you heat it for processing it melts and behaves like any other oil.
Shortening is fat used for baking and frying. Shortening is made from many kinds of vegetable oils, as well as lard and tallow. The oil is usually partly hydrogenated and different oils are blended for the desired effect.
For making biodiesel, treat shortening the same as hydrogenated oil.
Margarine and spreads are a blend of fats and oils with water, milk products, edible proteins, vitamins, salt, flavouring and colouring. Margarine is usually only 80% oil or fat or less. Extracting the triglycerides from the other liquids and proteins to make biodiesel is not easy. Margarine is best avoided.
Next: Oil yields and characteristics - Page 2
-- Quality standard for rapeseed oil fuel
Biofuels
En español -- Biocombustibles, biodiesel
Biofuels Library
Biofuels supplies and suppliers
Biodiesel
Make your own biodiesel
Mike Pelly's recipe
Two-stage biodiesel process
FOOLPROOF biodiesel process
Biodiesel processors
Biodiesel in Hong Kong
Nitrogen Oxide emissions
Glycerine
Biodiesel resources on the Web
Do diesels have a future?
Vegetable oil yields and characteristics
Washing
Biodiesel and your vehicle
Food or fuel?
Straight vegetable oil as diesel fuel
Ethanol
Ethanol resources on the Web
Is ethanol energy-efficient?
High yield is not the only factor in farming, maybe not even the most important factor. See: How much fuel can we grow? How much land will it take?
Typical oil extraction from 100 kg. of oil seeds
Castor Seed 50 kgCopra 62 kg
Cotton Seed 13 kg
Groundnut Kernel 42 kg
Mustard 35 kg
Palm Kernal 36 kg
Palm Fruit 20 kg
Rapeseed 37 kg
Sesame 50 kg
Soyabean 14 kg
Sunflower 32 kg
Oil from algae
Algae yield is not included in the yield tables because, in spite of all the hype about yields of 20,000 gallons of oil per acre and even 100,000 gallons per acre and so on, biodiesel from algae is still something of the future, not of the present.
As of end-2011, there is no such thing as biodiesel from algae apart from a few laboratory samples. There are some hopeful signs, but technical obstacles remain, pilot projects are not yet feasible for production purposes, and the claims made for high yields have never been demonstrated and remain theoretical.
No doubt that will change, but it's been "just around the corner" for years. When it does emerge, it's very likely to be in the form of high-tech industrial-scale solutions, not for backyarders or farms or villages.
We're sad to be so negative about it, but there's a lot of confusion about biodiesel from algae.
Of course we encourage further research. We supported many early small-scale attempts to make biodiesel from algae, but none succeeded, because of multiple problems.
The Oil_from_algae online discussion group has been working for the last seven years exclusively on biodiesel from algae production and now has more than 2,000 members, but they have no ready solution as yet: "We do not know enough yet to write you an instruction book, please help us learn," writes the group leader. Strength to their arms, we hope they have a breakthrough soon. http://tech.groups.yahoo.com/group/oil_from_algae/
Yet many people believe that making biodiesel from algae is an existing option for them now, a tried-and-trusted, ready-to-use technology.
We often receive enquiries asking why our website doesn't provide full instructions and plans for making biodiesel from algae. The answer is that we provide information you can use, and there isn't any information you can use on making biodiesel from algae, it doesn't yet exist.
Oil or biodiesel from algae is not a do-able option, there are no tried-and-trusted methods, it is not a ready-to-use technology.
But that's not the impression you get from the large amount of sheer hype flying around about algal biodiesel.
Dr John Benemann, the scientist who literally wrote the book on biodiesel from algae, has called some of the claims being made for the technology and yields "bizarre" and "totally absurd". In a critique of algal biodiesel developments in May 2007, Dr Benemann wrote:
- "Microalgae
biofuels generally, and algae biodiesel production specifically, is
still a long-term Research and Development goal (likely about 10 years),
that will require at least as much funding as the ASP, if not more, and
success is, as for any R&D effort, rather uncertain."
The ASP was the U.S. Dept of Energy Aquatic Species Program, which ran for 18 years and cost $100 million.
Dr Benemann was the Principal Investigator and the main author of the ASP Close-Out Report, the book that sparked all the interest in biodiesel from algae: "A Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae", by John Benemann, John Sheehan, Terri Dunahay, Paul Roessler, July 1998, National Renewable Energy Laboratory, U.S. Department of Energy, 328 p, 3.5Mb pdf: http://www.nrel.gov/docs/legosti/fy98/24190.pdf
The Brussels-based biofuels and bioenergy network Biopact published a detailed 13,000-word critique of algal biofuels developments in January 2007, "An in-depth look at biofuels from algae", in order to "temper some of the unfounded and unsubstantiated enthusiasm surrounding algae".
The Biopact report says:
- "Sadly, after
decades of development, none of those projects have ever demonstrated
the technology on a large scale, let alone over long periods of time.
This is why it is time to have a look at the possible reasons as to why
algae biofuels are being talked about, but don't seem to get off the
ground. ...
"The claims that algae yield 'enormous' amounts of useable biomass, have never been demonstrated or substantiated. Algae production in photobioreactors has never left the laboratory or pilot phase and no energy balance and greenhouse gas balance analyses exist for biofuels obtained from such systems."
http://news.mongabay.com/bioenergy/2007/01/in-depth-look-at-biofuels-from-algae.html
Dr. Krassen Dimitrov of the Australian Institute for Bioengineering and Nanotechnology (AIBN, University of Queensland), who made an in-depth analysis of algae-to-biofuel concepts, concludes that a biodiesel-from-algae plant using the much-hyped industrial photobioreactor approach and operating at maximum efficiency is not economically feasible at fuel prices below US$800 per barrel.
"Hype surrounding some alternative energy startups sometimes disregards the laws of physics and other fundamental principles," he says.
See Scientist skeptical of algae-to-biofuels potential, Biopact, July 18, 2007:
http://news.mongabay.com/bioenergy/2007/07/scientist-skeptical-of-algae-to.html
Hope springs eternal, but don't hold your breath.
Other oil crops
NewCrop SearchEngine at the Center for New Crops & Plant Products at Purdue University -- Search for "oil". Results: "The following pages containing 'oil' were found -- hits 1-20 of 200". Results are hyperlinked to detailed factsheets.http://www.hort.purdue.edu/newcrop/SearchEngine.html
Plants For A Future -- Database Search -- See "Search by Use - Select any of the following uses. Or select none and use the plant criteria below." Select "Other Use" - oil. Results: "Other Use: Oil (460)". Results are hyperlinked to detailed factsheets.
http://www.ibiblio.org/pfaf/D_search.html
Oils and esters characteristics
number |
number |
||||
Ester |
Ester |
||||
| Rapeseed oil, h. eruc. |
5
|
0
|
-2
|
97 to 105
|
55
|
| Rapeseed oil, i. eruc. |
-5
|
-10
|
-12
|
110 to 115
|
58
|
| Sunflower oil |
-18
|
-12
|
-14
|
125 to 135
|
52
|
| Olive oil |
-12
|
-6
|
-8
|
77 to 94
|
60
|
| Soybean oil |
-12
|
-10
|
-12
|
125 to 140
|
53
|
| Cotton seed oil |
0
|
-5
|
-8
|
100 to 115
|
55
|
| Corn oil |
-5
|
-10
|
-12
|
115 to 124
|
53
|
| Coconut oil |
20 to 24
|
-9
|
-6
|
8 to 10
|
70
|
| Palm kernel oil |
20 to 26
|
-8
|
-8
|
12 to 18
|
70
|
| Palm oil |
30 to 38
|
14
|
10
|
44 to 58
|
65
|
| Palm oleine |
20 to 25
|
5
|
3
|
85 to 95
|
65
|
| Palm stearine |
35 to 40
|
21
|
18
|
20 to 45
|
85
|
| Tallow |
35 to 40
|
16
|
12
|
50 to 60
|
75
|
| Lard |
32 to 36
|
14
|
10
|
60 to 70
|
65
|
Liberty Vegetable Oil Company lists the fatty acid composition of their oils as well as other details such as the Iodine Value, SG, Flash point etc -- Sweet Almond Oil, Pecan Oil, English Walnut Oil, Hazelnut Oil, Macadamia Nut Oil, Soybean Oil, Oleic Sunflower Oil, Canola Oil, Peanut Oil, Sunflower Oil, Corn Oil, Safflower Oil, Soybean Oil (Non-GMO), High Oleic Oils including Canola and Safflower. http://www.libertyvegetableoil.com/products.html
Iodine Values
Chemically, vegetable and animal oils and fats are triglycerides, glycerol bound to three fatty acids. Animal fat such as tallow or lard is saturated, meaning that in the fatty acid portion, all the carbon atoms are bound to two hydrogen atoms, and there are no double bonds. This allows the chains of fatty acids to be straighter and more pliable so they harden at higher temperatures (that's why lard is a solid).
As you increase the number of double bonds in a fatty acid, you reduce that ability for oils to gain a conformation that would make them solid, so they remain liquid. To picture it, imagine that you put a bunch of strings in a line. Now tie knots in various places on the strings and see how they don't fit together tightly.
To test a vegetable oil to see how many double bonds it has (how unsaturated it is) iodine is introduced to the oil. The iodine will attach itself over a double bond to make a single bond where an iodine atom is now attached to each carbon atom in that double bond. Higher iodine numbers do not refer to the amount of iodine in the oil, but rather the amount of iodine needed to "saturate" the oil, or break all the double bonds. Oils for the most part contain only trace amounts of iodine naturally.
How does this translate to biodiesel? When the fatty acid chains are broken from the glycerol and then re-esterified to methyl or ethyl groups, those fatty acids still have their double bonds. That means that the more double bonds, the lower the cloud point because they resist solidifying at lower temperatures. So, for instance, if you use lard or tallow, the biodiesel will solidify at a higher temperature because the fat it was formed from also solidified at a higher temperature.
(Image and text compliments of Jeff Welter)
High Iodine Values
See also Oxidation and polymerisationThe information below refers to straight vegetable oil fuel, but is also useful to show which oils are suitable for making biodiesel and which may not be suitable.
- Many vegetable oils
and some animal oils are 'drying' or 'semi-drying' and it is this which
makes many oils such as linseed, tung and some fish oils suitable as
the base of paints and other coatings. But it is also this property that
further restricts their use as fuels.
Drying results from the double bonds (and sometimes triple bonds) in the unsaturated oil molecules being broken by atmospheric oxygen and being converted to peroxides. Cross-linking at this site can then occur and the oil irreversibly polymerises into a plastic-like solid.
In the high temperatures commonly found in internal combustion engines, the process is accelerated and the engine can quickly become gummed-up with the polymerised oil. With some oils, engine failure can occur in as little as 20 hours.
The traditional measure of the degree of bonds available for this process is given by the 'Iodine Value' (IV) and can be determined by adding iodine to the fat or oil. The amount of iodine in grams absorbed per 100 ml of oil is then the IV. The higher the IV, the more unsaturated (the greater the number of double bonds) the oil and the higher is the potential for the oil to polymerise.
While some oils have a low IV and are suitable for use as fuel without any further processing other than extraction and filtering, the majority of vegetable and animal oils have an IV which may cause problems if used as a neat fuel. Generally speaking, an IV of less than about 25 is required if the neat oil is to be used for long term applications in unmodified diesel engines and this limits the types of oil that can be used as fuel. The table below lists various oils and some of their properties.
The IV can be easily reduced by hydrogenation of the oil (reacting the oil with hydrogen), the hydrogen breaking the double bond and converting the fat or oil into a more saturated oil which reduces the tendency of the oil to polymerise. However this process also increases the melting point of the oil and turns the oil into margarine.
As can be seen from the table below, only coconut oil has an IV low enough to be used without any potential problems in an unmodified diesel engine. However, with a melting point of 25 deg C, the use of coconut oil in cooler areas would obviously lead to problems. With IVs of 25-50, the effects on engine life are also generally unaffected if a slightly more active maintenance schedule is maintained such as more frequent lubricating oil changes and exhaust system decoking. Triglycerides in the range of IV 50-100 may result in decreased engine life, and in particular to decreased fuel pump and injector life. However these must be balanced against greatly decreased fuel costs (if using cheap, surplus oil) and it may be found that even with increased maintenance costs this is economically viable.
| Oils and their melting points and Iodine Values | ||
melting point deg C |
||
| Coconut oil | ||
| Palm kernel oil | ||
| Mutton tallow | ||
| Beef tallow | ||
| Palm oil | ||
| Olive oil | ||
| Castor oil | ||
| Peanut oil | ||
| Rapeseed oil | ||
| Cotton seed oil | ||
| Sunflower oil | ||
| Soybean oil | ||
| Tung oil | ||
| Linseed oil | ||
| Sardine oil | ||
-- From "Waste Vegetable Oil as a Diesel Replacement Fuel" by Phillip Calais, Environmental Science, Murdoch University, Perth, Australia, and A.R. (Tony) Clark, Western Australian Renewable Fuels Association Inc.
http://www.shortcircuit.com.au/warfa/paper/paper.htm
Note: More Iodine Values here.
Talking about the weather
Generally, the higher an oil's Iodine Value, the lower the temperature at which it solidifies. Different terms are used for this -- melting point (MP), cloud point (CP), cold filter plugging point (CFPP), and pour point (PP). In practice they all mean about the same. It matters with both SVO systems using straight vegetable oil as fuel and with biodiesel, but more so with SVO systems.As vegetable oils cool, wax crystals form, and the oil goes cloudy. The crystals can form a film on filters, blocking the flow of fuel. The temperature at which this occurs varies widely according to the oil type, from well below freezing point to well above freezing point.
It even varies for the same type of oil: new food-grade rapeseed or canola oil is usually "winterized" so that it doesn't cloud in the fridge and put people off. It will work nicely down to -10ºC, but once it emerges from the fryer, partly hydrogenated, degraded and probably containing some tallow from the food fried in it, it will only stay liquid and not plug filters down to freezing point or just above.
If you want to use an SVO system in a cold climate, you need a system configured to deal with the CFPP factor, and you need oil with a low CFPP. Coconut oil, palm oil, tallow and lard won't do, rapeseed or canola, corn or cottonseed are much better. (Peanut oil is an exception -- see Which oil is best?)
But if you live in a hot climate, cloud points won't bother you and the opposite is true: coconut and palm oil, tallow and lard all have higher cetane numbers than the others, and lower Iodine Values.
For biodiesel, the same applies, but to a lesser degree -- with most oils and fats, converting it into biodiesel tends to lower the CFPP. Biodiesel made with ethanol usually has a lower CFPP than biodiesel made with methanol. Additives and fuel-line heaters can solve the problem, and so can adding a proportion of petro-diesel or kerosene (up to 30% is usually recommended).
See: Biodiesel in winter
Summary
Vegetable and animal fats and oils are triglycerides, made up of three fatty acid chains linked to a molecule of glycerol.The fatty acids can be saturated or unsaturated. Unsaturated fatty acids have carbon-to-carbon double bonds. In saturated fatty acids all the carbon atoms are linked to two hydrogen atoms and there are no double bonds.
The degree of saturation is indicated by the Iodine Value of the oil (IV). Low-IV oils are more saturated with fewer double-bonds (lard, tallow, palm oil, coconot oil). High-IV oils are more unsaturated with more double-bonds (linseed oil, tung oil, some fish oils and other "drying oils").
Low-IV oils have higher cetane values and are more efficient fuels than high-IV oils, but they also have higher melting points and are usually solid at room-temperature. Biodiesel made from low-IV oils also has a higher melting point and might only be suitable for use as summer fuel.
High-IV oils have lower melting points and make better cold-weather biodiesel, but with high-IV oils there is more risk of the biodiesel oxidising and polymerising (drying) into a tough, insoluble plastic-like solid. Biodiesel made from high-IV oils should be stored carefully and used quickly.
"Semi-drying" oils like soy and sunflower are also prone to oxidation and polymerisation, though not as quickly as the drying oils.
See also Oxidation and polymerisation
Storing biodiesel
Hydrogenated oil, shortening, margarine
(See above, Iodine Values) Biodiesel freshly made from vegetable shortening (Todd Swearingen) |
When oils are hydrogenated hydrogen atoms are added to the carbon-to-carbon double bonds in unsaturated fatty acids, which then become saturated. This results in higher melting points. Fully hydrogenated oil is solid at room temperature, partly hydrogenated oils range from liquid to creamy to solid.
Hydrogenation also lowers the Iodine Value (IV) of the oil. "The typical IV for unhydrogenated soybean oil is 125-140, for foodservice salad and cooking oils made from partially hydrogenated soybean oil it is 105-120, for semi-solid household shortenings made from partially hydrogenated soybean oil it is 90-95." (Institute of Shortening and Edible Oils.)
So biodiesel made from hydrogenated oil is less likely to oxidise and polymerise but will have a higher melting point than if it were made from unhydrogenated oil of the same kind. It increases the risk of filters plugging in cold weather or even just cool weather and is best used as summer fuel.
In processing, treat hydrogenated oil the same as ordinary oil. The more solid it is when you get it the more difficult it is to handle, but once you heat it for processing it melts and behaves like any other oil.
Shortening is fat used for baking and frying. Shortening is made from many kinds of vegetable oils, as well as lard and tallow. The oil is usually partly hydrogenated and different oils are blended for the desired effect.
For making biodiesel, treat shortening the same as hydrogenated oil.
Margarine and spreads are a blend of fats and oils with water, milk products, edible proteins, vitamins, salt, flavouring and colouring. Margarine is usually only 80% oil or fat or less. Extracting the triglycerides from the other liquids and proteins to make biodiesel is not easy. Margarine is best avoided.
Next: Oil yields and characteristics - Page 2
-- Quality standard for rapeseed oil fuel
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