
How to make Biodiesel?
Vegetable oil will react very similarly to diesel fuel under the conditions inside a diesel engine; i.e. when it is highly compressed, it will heat up and ignite, causing the air in the cylinder to expand, and to push the pistons, in time. If you burned straight unprocessed vegetable oil, however, the fatty acids in the oil would start to congeal and harden (coke up) on the inside of your engine as well as in your fuel injectors, eventually leading to big, expensive engine problems.
Therefore, it is necessary to process your oil to remove the fatty acids-- making the oil more similar to diesel compositionally, or to otherwise devise a system to keep your engine clean of residues from unprocessed oil.
Following is our procedure for edible waste oil transesterification, which we used on our cross country trip. Please always use extreme caution when working with these ingredients.
-We are not automotive engineers, chemists nor scientists of any type so this information is still in a crude, explorative stage. Experiment to find what works for you.
-This information was collected from various individuals and has been used by us BUT by no means do we hold any responsibility for anyone attempting to do this process. Essentially this is public information to be used at your own discretion and risk. There is information available regarding transesterification and biodiesel. It is highly recommended to cross-reference and /or to contact someone in the organic chemistry department at a local university.
-This information shall not be resold to any individual but given freely to all who may inquire about this procedure.
-Lye is also very toxic and burns the skin upon touch. It is also extremely damaging if ingested. It is possible, however to set up a safe means of being able to mix fuel. An outdoor area is preferable or a space with plenty of ventilation. Access to electricity and water are both necessary. Have lots of newspapers and detergent on hand.
-Always mix a small batch first in an old blender to test your ratios. If successful the amounts can be multiplied directly.
NEVER EVER USE ANY OF THE UTENSILS, POTS NOR BLENDER FOR LIQUID NOR FOOD CONSUMPTION AGAIN!!!
To determine your proportions, figure:
The number of drops of NaOH needed for the WVO solution to reach a ph of 8-9 1 ml. plus 3.5 g. NaOH to catalyze the oil
An example formula used with one particular batch of WVO-wasted vegetable oil.
1 ml of oil was titrated with a 1g NaOH/1000 ml H2O solution.
It required 6.0 ml to raise the ph level to 8 = .006g
so 6.0g/1000ml to neutralize the free fatty acids
plus 3.5 g NaOH as catalyst
= 9.5 g per 1000ml oil or 9.5g/915g oil=103% by wt.
Lye: (Sodium Hydroxide ((NaOH)-- or potassium hydroxide also works) is the catalyst for transesterification. It works by "cracking" the vegetable oil molecules, splitting the triglycerides from the hydrocarbons and shortening the carbon chain. (3.5g or .35% is the standard amount of lye necessary to create a reaction, when using fresh vegetable oil, so you can figure that used vegetable oil will always use more.)
Methanol: The amount of methanol needed will also vary, but the ideal is to use the least amount of methanol necessary in order to get the highest yield. The yield is related to completion; so if you get a 90% yield that means that 90% of the fatty acids have been eliminated
from the vegetable oil. We have found that the best is to use 15% to 20% methanol, based upon the total weight of your batch of oil.
*it is best to use dry gas methanol (we found methanol at an automotive racing store)
A hydrometer can also be used to check the amount of completion according to density
This combined mixture makes Sodium Methoxide. Add this to the WVO and mix for 40-60 minutes. We used a dry wall mixer bit attached to a 1/2 foot drill to do the mixing
NOW---Draw out samples every 5-10 minutes to check the rate of separation. The cloudy looking free fatty acids, called glycerine, will sink to the bottom and the methyl esters--a translucent liquid, will remain on top. When the separation appears not to be advancing any more, stop mixing. Let the mixture settle for at least 8 hours.
The liquid you have on top now is methyl ester, but before using it you have to remove any remaining soaps or salts which could cause engine damage . The glycerin which has sunk to the bottom should be disposed at your local toxic waste disposal site.
RINSING METHYL ESTER: Pour off the methyl ester into a separate clean container, so it can be washed free of any remaining soaps, salts or free fatty acids.
Add water to the methyl ester. Stir slightly and then allow mix to settle. When the water has cleanly separated from the methyl esters, drain or pump the water out from the bottom. Repeat until the discarded rinse water reaches ph level of 6-7 -- and no soap bubbles appear.
If the liquid is cloudy, there is water being retained in the fuel, and it will need to be reheated slowly to evaporate out the water. Any white substances forming at the bottom or any bubbles forming at the surface is a sign of soaps and should be removed or the liquid should be re-washed. The cleaned methyl esters are now a homemade version of biodiesel and are ready to go into your diesel tank.
ONE MORE WARNING: To use 100% Biodiesel for longer than 4 weeks straight will cause complications to any rubber components of the engine that the fuel might come into contact with-fuel pump, hoses, o-rings, etc. These can either be replaced with steel or heavy duty rubber or.. it is recommended to use a percentage of diesel with your homemade fuel- at least 20%.
HAPPY MOTORING! Check out VeggiePower.org
In terms of efficient energy production and overall carbon dioxide emissions, biodiesel trumps not only conventional diesel, but also gasoline and gasoline’s bio-fuel substitute, ethanol.
For example, according to a study by the Minnesota Department of Agriculture, biodiesel produces 3.2 units of energy for every unit of fossil-fuel-energy consumed in its production. Ethanol yields a lower 1.34 units of energy, while gasoline and conventional diesel represent a negative yield. (The influx of solar energy into the organic resources—corn, soy, etc.—that will eventually become ethanol or biodiesel accounts for their positive energy yield.) The efficiency of the four fuels breaks down as follows:
FUEL |
ENERGY YIELD* |
NET ENERGY (LOSS) OR GAIN |
Biodiesel** |
3.20 |
220 percent |
Ethanol |
1.34 |
34 percent |
Petrodiesel |
.843 |
(15.7 percent) |
Gasoline |
.805 |
(19.5 percent) |
* expressed in Btus per Btu of fossil fuel energy consumed over its life-cycle
** A WorldWatch study, released in June, found an even greater energy yield for biodiesel produced from waste vegetable oil only, averaging between 5 and 6 Btus per Btu of fossil fuel.
Another study, by the US Department of Energy, reveals a similar hierarchy of fuels, as ranked by their life-cycle carbon dioxide emissions:
FUEL |
CO2 EMISSIONS (LBS./GALLON) |
Biodiesel |
5.84 |
Ethanol |
14.60 |
Gasoline |
24.30 |
Petrodiesel |
26.55 |
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