ADVENTURES IN BIOFUEL
When I was growing up my mother taught me to cook. And one thing she taught me was to pour off the leftover cooking grease into a small container on the stove. When the container was full, she would dump it into the trash. My mother explained to me that the grease wasn't good for cooking with and would clog the drain if it went into the sink when washing the pots and pans. This seemed like good advice, but it also seemed wasteful to me. 'Surely,' I thought, 'the grease must be useful for something.' And the effort to collect it seemed lost too.
So, after I began cooking on my own, I emulated my mother for awhile. However, my engineering background made me very averse to waste. It irked me to throw away the grease and expend the effort to collect it with no benefit. Then it dawned on me that perhaps if the grease were filtered, it would be good for something. So, I collected about a half a gallon of grease, melted it on the stove top and filtered it through some coffee filters into a large container. I ended up with about 5 or six pounds of lard. It was tinted beige compared to white store-bought lard, but looked OK for cooking with. I decided to try deep frying some home-fries in it and see how they turned out.
The fries looked fine and smelled OK, but they tasted a bit greasy and meaty. It was not a great success. In an emergency this would do, but there was no grand shortage of cooking oil to justify this sort of economy. The idea of making soap out of the grease didn't appeal to me either. I doubted the real cleansing power of something made from used cooking grease.
What else could I do? I searched the internet for ideas. Biofuel!
That seemed simple enough. Biodiesel could be made by heating the grease to about 130 degrees F, and adding a mixture of methanol and lye called methoxide to the liquid grease. In a few hours they would separate into biodiesel and glycerine.
I decided to run three trials:
1. with store bought methanol and lye
2. with store bought methanol and home made lye, and
3. with home made methanol and home made lye
So, I collected about 1.5 gallons of grease to make half gallon batches of each. This took a few months of collecting cooking grease.
To calculate the amount of lye needed, it was necessary to determine the pH of the grease/methanol mixture. The pH of grease cannot be read directly with a common pH meter. So I mixed up a small batch of 100 ml: 80% grease and 20% methanol. I bought the methanol from a local auto parts store that sold it as a fuel additive. (These are the proportions commonly used for making biodiesel.) Then I titrated it with a 10% lye solution. As an indicator, I used some turmeric spice that was on hand. In an acidic solution, turmeric maintains its pale yellow color. When the solution goes basic, it turns a reddish color. I had a graduated syringe left over from vaccinating our dog, and used it to measure out the volume of 10% lye solution necessary to titrate the grease/methanol mixture.
It went something like this:
80 ml hot grease + 20 ml methanol = 100 ml of test solution
10 grams lye + 90 grams (9 ml) water = 10% lye solution
1 g turmeric as indicator
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| BIODIESEL BATCH NO. 1 |
it took 2.5 ml 10% lye solution to neutralize the test solution
(2.5 ml)*(1g lye/ml)*(2000 ml biodeisel-methoxide mixture)/(100ml sample BM mix) => 50g lye
I added 60g lye to the methanol just to be sure there was enough for a complete reaction since rarely do 100% of the chemicals in a mixture react. When I added the commercial lye to the methanol I was surprised to see aluminum shavings mixed in with the lye. Apparently the manufacturer added these to make the lye foam when it was poured into a clogged sink pipe. That may be good for unclogging pipes, but it didn't fit my recipe for bio-fuel. So I had to quickly filter out the aluminum chips before they dissolved in the methoxide. To do this, I put a coffee filter in a funnel, and poured the mixture into another container. (empty spaghetti sauce bottles turned out to be handy for this.)
The first batch used 8 cups grease and 2 cups methoxide in a half-gallon glass jar. Before adding the methoxide, I heated the grease up to 130 deg F, checking the temperature with a cooking thermometer. In a well ventilated area, gloved, and with safety goggles on, I slowly added the methoxide to the warm grease and stirred it with a stainless steel spoon. The reaction produced about 7 cups biodiesel and 3 cups glycerine.
These had effectively separated after about three hours when I left the mixture to cool. To be sure of complete separation, I left the batch to sit overnight. The biodiesel on top was a clear amber and the glycerine (which sank to the bottom) was a dark, opaque brown. After they had fully separated, I poured off the biodiesel and "washed" it by adding a cup of clean tap water and shaking the mixture vigorously. The mixture turned a murky yellow. I let it sit overnight and most of the water settle out. The water separated out on the bottom and turned milky with soap. The washed biodiesel remained a murky yellow color. It appears not all the water separated out. Then I decanted the biodiesel into a separate container.
The final test came when I looked for a way to actually use the biodiesel. I'd read that it could be used directly in a diesel engine, or mixed 3:1 gasoline/biodiesel and used in a gasoline burning engine. However, I don't own a device with a diesel engine, and a tax must be paid to the federal government before using home made fuel in a motor vehicle on public roads.
So, I decided to try it out in some other device. I chose the lawn mower. Our old HRS21 is due for retirement, so if the experiment damaged the engine, no great loss. Just to be sure it still ran, I warmed it up on straight gasoline before the trial.
The fuel mixture used was one cup biodiesel to three cups premium gasoline. There appeared to be some sediment in the mixture - perhaps a precipitate from mixing the two fuels. So, I filtered the mixture through a coffee filter before adding to the fuel tank on the lawn mower. Finally the great moment, years in the making, was at hand. Would it run?
The warmed up mower cranked smoothly and ran on the first pull of the cord. It seemed underpowered, so I tweaked the choke until I found the optimal setting. Then I began cutting grass! The mower seemed under powered and stalled frequently. So I stopped the engine, sharpened the blade (which was dull) and resumed cutting. This helped, but the engine still knocked or stalled in the areas of tall, thick grass.
I ran the tank dry cutting the lawn and refilled it again with the same mixture. The second time I ran the mower it appeared to run nearly full power. The reason for this was not apparent. Though I have heard claims that the soap residue in the biodiesel has an added benefit of cleaning out the carburetor and engine. Perhaps this improved the performance. I'm not sure. My long experience mowing with this mower indicated that the trial fuel mixture delivers less power than straight gasoline. But, in the absence of a handy dynamometer, I can only guess at the difference. My best guess would be that the engine Hp is reduced about 10-15% with the biodiesel/gasoline mixture. With a 5 Hp engine it is certainly adequate for cutting the grass though.
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| SAMPLES: L TO R: BIODIESEL / FUEL MIX / GASOLINE |
I still need to build a device to destructively distill wood to make my own methanol. so the third trial will have to come later.
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| HOME MADE LYE |
In the meantime, I need to figure out what to do with the left over glycerine. Soap perhaps? I need to look into some kind of distilling apparatus before I'll use that for soap. I've read that the lye can be recovered too. That sounds like a thing to look into.
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