By Carl Benson

I collect waste vegetable oil (wvo) from two local diners. These two places are preferred because they filter their used fry oil and store it in the plastic 5-gallon containers the vegetable oil originally came in. It is easy for me to pick up these containers on a weekly basis in the back of my pickup truck. I have received offers of wvo from other sources that I ended up turning down because of poor quality product…ie: water in the oil or unfiltered oil with a lot of solids in it. I have two other recent sources that are joining forces to actually deliver the oil to our farm! I have not charged for picking up wvo as some other bio-diesel producers have suggested, since we are already benefiting from the product they are providing. Normally diners and restaurants pay a substantial fee to a waste removal service to take the wvo.
Since it is an hour round trip for me to pick up the oil once a week, I almost never make the trip just for the oil. I combine any other town chores to make the trip more efficient. This is why the cost for gas in picking up the wvo listed under supplies and ingredients is so low. Additionally one of the diners is conveniently located directly behind one of the farmers’ markets we attend so pickup there during the market season doesn’t involve an extra trip. We just toss the jugs in the truck before we leave the market. We receive about 30 gallons of wvo from our two main sources each week. Although we combine wvo pickup with other chores let’s allocate a full one-hour to this category.

Titration and test batches
Doing the titration is necessary to determine the amount of NaOH (Lye) to use in the test batch and during the actual processing later. Doing a test batch or mini batch is simply a way to test the results of the titration without committing to a 50-gallon error.
The titration is accomplished by dropping NaOH solution in one ml increments into a solution of wvo and isopropyl alcohol. The pH of the solution is checked after each 1 ml is added. When pH jumps to around 8 or 9 the titration is considered finished. A simple calculation reveals how much lye to use in the mini batch. The titration usually takes me about 30 minutes, including cleanup time.
Doing a test or mini batch involves blending a liter of wvo with a mixture of methanol and lye. The methanol and lye are mixed first yielding methoxide. The methoxide is then blended with the wvo for 15 minutes. The whole blending process and cleanup takes about another 30 minutes. I pour a liter of the mixture into a large graduated cylinder for settling. Most of the settling occurs in the first 90 minutes so you have a pretty good idea of how the process went well before the full eight hours of settling time are over. Making the test batch takes about 30 minutes not counting the settling time.

Processing large batches

Doing the big batch goes like this: I fill a steel 55-gallon drum with 50 gallons of wvo, filtering it through a pair of pantyhose to remove any solids that are in the oil. The steel drum is set up on three cinder blocks above a two- burner propane hotplate. After filling the drum the oil is heated to 120°F. This takes about 1 1/2 hours. While the oil is heating put 10 gallons of methanol and the appropriate amount of lye into the 20 gallon mixing tote. The amount of lye will vary depending on the results of the titration, and test batch. You may end up using between 30 and 50 ounces of lye for a 50-gallon batch. Exercise great caution when handling the methanol and lye. Methanol is highly toxic, and lye is extremely caustic. You don’t want this stuff on your skin!
I drilled a hole in the center of the lid that fits onto the tote so that I could pass a drywall mixing rod through the lid and into a 1/2-inch drill. Using the drill and mixing blade I mix the methanol lye solution for about 5 minutes until there is no unmixed lye left. Note that the lid stays on the mixing tote…the methoxide fumes are caustic and very bad to breathe. A respirator is recommended!
When the wvo is up to temperature I pump it into the mix tank where it is combined with the 10 gallons of methoxide, and mixed with the electric motor and mixing rod combo. The mixing takes about an hour and I always use this time to clean up or work on some other task. Once the mixture has been agitated for an hour the mix motor is turned off and the reaction is allowed to go to completion and settle for 8 to 12 hours. As soon as the mixer is turned off I immediately take a one-liter sample so I can see how well the reaction went. My mix tank is opaque which I thought would allow me to see the glycerin settling out but the plastic is just too thick to see through. Instead, we just take the sample and put it into a 1 liter graduated cylinder which is easy to see through! Not only is this sample handy as a visual indicator of how your batch has turned out but you can also test the viscosity or specific gravity with a hydrometer. Bio-diesel has a specific gravity of around 0.88 at room temperature.
I usually get about 10 gallons of glycerin as a byproduct. The rest is bio-diesel! We have a stopcock type valve on the bottom of the mixing vessel, which is handy for draining off the liquids from the bottom as opposed to having to pump or siphon from the top. I drain the dark thicker glycerin into the same 5- gallon jugs that the vegetable oil came in when I picked it up at the diners. As I am drawing off the byproduct we watch for the color and viscosity change to a thinner golden colored liquid typical of biodiesel fuel. At this point I draw off the fuel into clean 5 gallon buckets and empty them into a 55 gallon drum that is already stationed on the 3 point hitch platform that attaches to the back of the tractor.
The heating, mixing and drawing off into the transportable drum take about 3 hours.

Transferring to tanks
Now that I’ve made 50 gallons of biodiesel I can put it directly into the fuel tanks that I have inside the greenhouses. My fuel storage consists of standard 275- gallon oil/kerosene fuel tanks that are available new through most fuel companies and used just about anywhere.
With the new fuel in our transport drum and the lid clamped down tight we are ready to move the fuel to the greenhouse. It is a simple matter to back the tractor up, attach the platform, and bring the fuel around to the back of the greenhouse. I pass the delivery end of the rotary hand pump hose through a flap in the end wall plastic and into the fuel tank, and start pumping. It takes me about 15 minutes to get the fuel from the barn and into the fuel tank.
All together it takes about 5.5 hours of actual work time to make and move a 50-gallon batch of biodiesel. Making larger batches seems the logical way to cut down on the time involved.

Locating the fuel tanks
I locate the tanks inside the greenhouses because it is best to keep this fuel warmer than heating oil. Biodiesel has a higher cloud point than does heating oil/diesel. This means that biodiesel will cloud up, eventually gelling at warmer temperatures than heating oil/diesel. Standard heating oil/diesel will cloud at 20 degrees F. Biodiesel cloud points are highly variable depending on the oil they are made from. Biodiesel fuel made from used vegetable oil will cloud at higher temps than that made from unused vegetable oil. Since clouding and gelling will negatively affect furnace performance a couple of strategies are recommended.
As most people who live in the north and heat with oil are aware, fuel companies will blend kerosene with their product as winter approaches. The kerosene lowers the gel point of the oil it is blended with. Likewise, biodiesel can be blended in any ratio with fuel oil or kerosene with no ill effects. Or one might choose to use standard heating oil early in the season and go back to biodiesel when warmer weather arrives.
I decided to move our fuel tanks inside the greenhouses to keep the fuel at a nice warm temperature so I would not have to rely on blends to keep my fuel liquid. We have tomato plants in the ground in the houses in April when there is still plenty of seriously cold weather and snow on the ground outside. I don’t want to risk the nightmare of having the furnaces quit on a frigid night just when we need them the most! Of course we are changing our seeding house over to a biodiesel fueled furnace this year. That house is up and running by the first of March when it is not unusual to see nighttime temperatures below zero here in the northeastern part of Vermont. So moving the tanks inside is a logical step.
There are regulations for distance between fuel tanks and furnaces. This distance is 60 inches. However it should be noted that diesel heating oil has a flash point of 125 degrees F while biodiesel’s flash point is much higher, 301 degrees F so while diesel is listed as explosive biodiesel is not considered explosive under normal circumstances. Still we try to maintain some distance between the fuel tanks and the furnaces.

Problems we encountered
We ran into a problem after we became over confident and stopped doing test batches. One day the furnace in one of the houses just quit! Although this was toward the end of the summer when we were just taking the edge off the nighttime lows it certainly caught our attention!
We removed the fuel filter between the tank and the furnace and found it was completely clogged with a jellylike substance. We had, over the course of the summer, become so confident in our basic “recipe” that we started eliminating the titrations and test batches…BAD MOVE! We had made soap, which actually burns quite poorly (surprise), and clogs fuel filters. In the system we had in the other greenhouse there was no fuel filter at all! This furnace also stopped working. The pores in the fuel nozzle on the “gun” were clogged, and the nozzle had to be replaced. At this point I learned not just a little lesson on oil furnace mechanics but also…DON’T SKIP THE TITRATIONS, DON’T SKIP THE TEST BATCHES! If this had happened early in the season when we needed those furnaces for severely low temperatures we would have been looking at some severely reduced farm income! Fortunately this wasn’t the case and the cost for a new filter cartridge and a new nozzle put us back by less than $8.
The only other hurdle we would like to overcome is the issue of the amount of time it takes us to produce the fuel we need for our greenhouses. If it takes us over 5 person hours to make a 50 gallon batch, and if we value that time at $10 per hour, that adds a steep dollar per gallon to our costs! OUCH! The only way to get around this, we believe is to make larger batches. It would take very little extra time to double or triple our batch size, effectively reducing time per gallon by half or two-thirds.
In any case, knowing that we can produce a bumper crop of early tomatoes for our customers at our markets and not have to depend on petroleum fuels to do it feels pretty good. Saving 25 to 40% on our fuel bills just makes it that much sweeter.

Recommended reading: From the Fryer to the Fuel Tank, The complete guide to using vegetable oil as an alternative fuel. By Joshua Tickell, published by Tickell Energy Consultants, Covington, LA 2000. Available from local bookstores or online at numerous booksellers.