How to Make your own Biodiesel
Being the tree hugger that I am, I am always interested in alternative ways to recycle, reduce waste and protect the air. I live in a very polluted city (Houston) and actually work as an environmental professional in the petroleum industry. I have been researching biodiesel and have taken a course on how to make it.
For the non-chemists in the group, biodiesel is a methanol molecule bonded to an ester molecule. The process begins with pure vegetable oil where there are three esters bonded to a single large glycerin molecule. To change this into biodiesel, the heavy glycerin molecule is replaced with three alcohols in a process called transesterfication. The esters are stripped out leaving behind a large glycerin molecule. The free esters will now readily bind with the free alcohol (usually in the form of methanol or ethanol). A catalyst is used to counteract the free fatty acids present in used oil. Once all these free fatty acids are otherwise disabled, the remaining oil can be make into methyl ester.
Biodiesel is a clean burning alternative fuel that comes from completely renewable resources. There is no petroleum in biodiesel but it can be blended with petroleum to be used in a variety of vehicles. It is non toxic and will degrade naturally. Pure biodiesel can only be used in diesel engines, not gasoline engines.
To start with, you will want to get waste vegetable oil (WVO) such as fryer grease only that which has fried vegetables or a small amount of meat - pure methanol and either sodium hydroxide (caustic soda) or potassium hydroxide (KOH). For the titration phase you will need pure isopropyl alcohol 91% minimum (common rubbing alcohol), phenolphthalein (you can get this from your local pool store) and distilled water. For the washing phase, you will need water. The oil should smell good and not be rancid. The more meat that the oil has fried, the more effort it will take to remove the free fatty acids.
Before starting to work with any chemicals, be sure to wear the proper protective clothing gloves, splash apron, goggles or face shield. Any work you do with these chemicals should be in a well ventilated area. Methanol is toxic and can be adsorbed through the skin; caustic soda is lye which will burn your skin.
FilteringFilter the waste vegetable oil (WVO) by pouring it through cheesecloth or industrial coffee filters. Be sure to remove all solids in the oil. You may need to heat the oil up to about 95 degrees Fahrenheit in order to get it to flow.
Test for Water ContentDepending upon your source for WVO, you may need to dehydrate, or remove the water. This can be done by heating the oil up to 212 degrees Fahrenheit and see if you get bubbles. If you do, that indicates there is water present. No bubbles is the preferable situation you want to see. In order to remove this water, once you have heated the oil to 212 degrees, you will want to hold the temperature at 180 degrees Fahrenheit for about an hour. Allow this to cool slowly. The oil and water will separate into phases and the water can be drained off the bottom.
TitrationThis is the hard part of making biodiesel. The titration will tell you how much catalyst in the form of caustic soda or KOH you will need for your particular oil. Remember not to allow any moisture to get to your catalyst; it will need to remain in an airtight container when not in use. Mix one gram of caustic soda or one gram KOH to one liter of distilled water and make sure it is completely dissolved. You may keep this mixture for future titrations so do not let it get tainted.
On a side note, caustic soda, or lye is very hard to obtain. With the increase in home made methamphetamine, stores have stopped carrying the ingredients needed to make it. Unfortunately lye was used in both the manufacture of this illegal drug as well as a catalyst in the production of biodiesel; therefore it is no longer readily available. KOH is much easier to purchase and has as of yet not been used to manufacture illicit drugs.
Next, mix ten milliliters of isopropyl alcohol with 1 milliliter of WVO in a small container. This 1 milliliter must be precise so as to allow you to extrapolate to the rest of the WVO. Add two drops of phenolphthalein - it will be colorless in an acid pH of less than 7 and red in a base, pH greater than 7. Using a graduated pipette or eyedropper, measure how many milliliters it takes to have this test solution turn pink and hold for at least ten seconds. You will need to vigorously stir the solution after each drop until you get the ten second color change. You will not want to exceed the pink phase's pH level or it will throw off the rest of the reaction.
CalculationEach milliliter of KOH/water of caustic soda/water is equal to 1 extra gram of either KOH or caustic soda you will need for your liter batch to get rid of the free fatty acids in the WVO. Since you will likely be making bulk quantities of biodiesel, you will need to extrapolate the amount of caustic soda or KOH you will need.For Caustic SodaNumber of liters of oil x (5 grams plus titration results)For example: if your titration showed 3 milliliters then you will add 3 extra grams for each liter of oil. If you have 100 liters of oil then the equation would be100 liters oil x (5 grams + 3 ml);100 x 8 = 800 grams caustic soda to make biodiesel with this oil.
For KOHThe titration results will be somewhat different than those with caustic soda. Here you will need 8 grams plus titration results.For example titration showed 4 ml for that oil sample then100 liters oil x (8 grams + 4 ml)100 x 12 = 1200 grams of KOH for this oil.
This is the basic recipe' to make biodiesel. Once you are ready to make a big batch, you will need a reaction vessel. You can purchase ready made reactors, the website http://www.biodieselcommunity.org/appleseedprocessor/ has examples of how to home construct one. Once you have a reactor, your oil, methanol, KOH, a titration kit and a wash tank it is time to get busy.
Load the reactor with oil and begin to heat to 120 degrees Fahrenheit. Try not to exceed 130 as this gets much too close to the boiling point of methanol. When you add the methoxide the temperature will rise so you will want to unplug the reactor when it reaches 120.
Titrate the oil you have and determine the quantity of KOH and methanol you will need. Prepare the mixture using 22% methanol (do not exceed 25%) and make sure all the KOH dissolves. Be sure you have your personal protective equipment on, are in a well ventilated area and have plenty of water available in the event of a spill. Turn on the process pump on the reactor and slowly add the methoxide mixture should take about 15 minutes to add 7.7 gallons. Mix with circulating pump for two hours.
Pre-wash process comes next. This is an optional step but is suggested as it will get you closer to the finished product. With the pump still running add 1.5 gallons of warm water slowly (tap water is fine) into the reactor. Continue to mix with the pump for another fifteen minutes. Shut off the pump and allow the mix to settle overnight. Drain off the glycerin from the bottom this is the dark brown or black layer. Pump the finished biodiesel into your wash tank.
Washing the biodiesel can be done several ways. You can use a mist, bubble washing (use an aquarium bubbler) or emulsion mixing. The water and biodiesel will separate out and again you can pull the waste material off the bottom. The goal is to pull the remaining glycerin out of the mix and leave the biodiesel behind. Once the product is complete, filter with a five micron filter and put into your diesel vehicle fuel tank.
