Make Your Own Biodiesel

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Clemson University Biofuels Coordinator David Thornton discusses production techniques, safety and quality control testing during a recent workshop at the Cherry Crossing Research Center located near the main campus.

Most oil-seed crops are going to be too valuable to make biodiesel out of it. If you grow soybeans or canola or rapeseed or sunflower seed, which are the common ones, or even peanuts, those have values of up to $10 a gallon or more. So how you turn a $10 a gallon culinary oil into a $3 fuel is by collecting it from deep fryers as used cooking oil. So that’s what we’re going use to make a batch of biodiesel fuel today—used cooking oil we collected from the dining halls on campus. And we’re going to load it in the reactor and do a whole batch today. But before we do that, I need to give you some background on what is biodiesel. The catch-phrase that I like to use is clean burning, renewable and domestically produced. It is clean burning with about 78 percent less emissions than diesel fuel. And it is renewable because it comes from plants or animals. So these are feed stocks which can be regenerated, unlike petroleum products which did once come from living organisms. However, that was 200 million years ago, so we don’t consider that a renewable fuel. The glycerol settles to the bottom. We drain the glycerol and we transfer the biodiesel over to a wash tank. Here you could add four different volumes of water and run it until the water is clear. Or you could do a dry-wash, which is where you inject air into the bottom and evaporate water out in that way. You test the moisture content, and if it’s below 1,000 parts per million, you can then run it through the ion exchange system. What’s going to happen is probably for about a 12-hour period you’re going to run air bubbles through this tank and evaporate the water and ethanol, and then you’re going to turn that system off and let it settle for about 12 hours. The soaps and glycerols will settle to the bottom, and you’ll pump them off and then test the moisture again. And then you’re going to pump through an ion-exchange system that will remove any of the glycerol or soap that remains in the solution. There are also filters involved, because as you remove the water and ethanol, it’s going to congeal and become really sticky, so you can remove a lot of it with a filter. Oil comes in, you remove the water and sediment, you heat the oil to 130 degrees, you mix up your methoxide, put the methoxide into the reactor and react for about two hours. Drain the glycerol. The biodiesel goes into the wash tank. You remove the water and methanol, then you pump it through filters and you wind up with a finished biofuel.
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