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Contact: biolyle@gmail.com 206-354-6802
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 Kuma Biodiesel Stoves
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I now use the “Appleseed” processing procedure as described at biodieselcommunity.org. This system utilizes an electric water heater as a reaction vessel. My system, shown above, has evolved naturally, as I've added things, such as the methanol recovery tank. I will describe my use of the appleseed system, including my modifications.
- To get started, I pour my oil thru a 200 or 400 micron screen to filter out any substantial food particles, into an open top drum.
- You could also simply use plastic window screening, since you really just want to filter out the big chunks, like french fries. My drum has a valve on the bottom and is up on blocks so it is at the level of bottom of my processor, making it easy to use the processor pump to suck in the oil as shown below (red handle on valve from oil drum to blue handle on processor valve).
- I used to use my 12 V pump to pump the oil into the Appleseed (a fine option):.
- Once the oil is in the water heater (processor), I turn on the mixing pump and the heat. [I recommend using an extra low density heating element which lasts much longer than conventional elements]. After mixing for an hour or so, I take a small sample for the titration. Since my oil comes from several sources, I want it all mixed together before titrating.
- Once the oil has started heating, and I've done the titration, it's time to get the methoxide mixture prepared. Since I am processing 50 gallons (188 liters) of oil at a time, I need 11 gallons of methanol (=22%).
KOH vs NaOH:
Although lye is more available and cheaper, there are several advantages to using potassium hydroxide (KOH) instead. The first is that KOH dissolves faster in the methanol. With the new bubble-mixing system described below, the KOH dissolves within a couple of minutes (literally 2 minutes!). Second, the glycerin produced as the byproduct of the reaction using KOH is liquid, even at cold temperatures, making it much easier to dispose of (compared to lye-based glycerin which can be semi-solid). Finally, the glycerin produced from KOH reactions is better for the environment, since potassium is a nutrient, whereas the sodium in lye is toxic to soil. Thus once you've removed the methanol, you can feel good about composting your glycerin. (And you could probably compost it even with some methanol- just don't put too much in). The disadvantages of using KOH are that it is more expensive (tho it's not very significant), and that handling it seems to create a more caustic dust, so wearing a respirator mask and eye goggles is important.
Methoxide prep:
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I am now using a great methoxide mixing method invented by my friends Bill Levin (pictured below) and Jack Donnelly. The required amount of methanol is added to a 15 gal conical tank, then the KOH is weighed out and added (there is a strainer in the conical tank to keep the KOH from cloging the opening at the bottom. Air is then bubbled thru a valve in the bottom, and the KOH is dissolved almost immediately (within 1 minute!). NOTE: This method should only be used for KOH; it doesn't work so well for NaOH, since the grains are much smaller and get through the colander. If using lye, dissolve it in 5 gal HDPE carboys as described here.
 - After adding the methanol to the 15 gal conical, it's time to weigh out the required amount of KOH. Most of the literature says to use 7 g KOH per liter of oil plus titration amount, but with some coaching and testing by a small commercial biodiesel producer, I am now using 11 g KOH per liter as the base amount. Increasing the KOH to 11 g per liter has lowered my total glycerin number in the finished biodiesel to be under the ASTM standard of 0.24.
- Add the required amount of KOH to the methanol. If my oil titrates at 2 g KOH per liter, then 2 + 11 g (base amount) = 13 g per liter oil. Multiply 13 g times 188 liters of oil (50 gal) = 2444 g KOH required to process the 50 gal of oil.
- You'll notice the methoxide tank gets quite warm- that's because the reaction of lye or KOH and methanol releases some heat, i.e. it is exothermic. . By the time the oil is up to the proper temperature (130-140 deg F, or 55 -60 deg C), the methoxide mixture can be fed into the processor. Note that the flash point of methanol is 148 degrees F, so you'll want to keep the temperature no higher than 140 deg F (60 deg C).
Reaction:
- When the oil in the processor has reached 130-140 deg F (55-60 deg C) turn off the heating element. Open the valve to feed the methoxide into the processor containing the hot oil. After feeding all the methoxide into the processor, allow the pump to mix for a couple of hours. I have even left mine overnight, if I didn't set up the reaction till late in the evening.
 After reacting, I pump the contents of the processor into a 60 gallon conical plastic holding tank. Plastic tanks are not as safe as metal ones, but as long as your liquid is in the 130-140 deg F range (55-60 deg C) the tank is safe. I like the conical bottom because all of the glycerin gets funneled out very easily. I also like being able to see through the translucent tank to see how much glycerin was produced, and to see the water level during washing. Check out the standpipe wash tank preferred by Girl Mark and others. - Drain the glycerin out of the conical tank after letting it settle overnight. Glycerin will continue to accumulate for several days- just drain it once a day until hardly any is coming out. I routinely do this for 3 - 4 days, and then begin the washing process. The glycerin contains a lot of the soap formed in the reaction as a byproduct, so it's a good idea to get rid of most of it before starting to wash. Another trick is to bubble and mildly heat the unwashed biodiesel before starting the water wash. By doing so, much of the unrecovered methanol will be driven off, which keeps soaps in solution. By bubbling at a warm temp (110 - 120 deg F), your wash will go a lot faster and use less water. To heat the biodiesel in the wash tank, I use an aquarium heater made of titanium with a plastic cap (made by ProHeat- find these easily on ebay).
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