November 5th, 2007

How To Tuesday: Make Your Own Biodiesel

Posted by Dan Sharp

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Yes, you really can make biodisesel from used cooking oil in your garage for less than a buck a gallon. It takes a bit of research and determination to set up a processor, but once you’re up and running it becomes another simple task to complete as part of the weekend chores. If you’re interested in the process of making biodiesel, keep reading. Skip to the end if you just want to know about how to buy biodiesel and its environmental benefits.

A huge misconception is that biodiesel is the same as vegetable oil. Making biodiesel is really creating a chemical reaction that changes vegetable oil into biodiesel. Here are the basic steps involved:

1.  Get some used vegetable oil. Anywhere that has excess oil that’s liquid at room temperature is a good place to start (although I have a preference for oil from restaurants serving Asian cuisine). There are several sources online that give tips about how to get a good source.
2.  Filter out the chunks. Used cooking oil will have leftover tempura, fried chicken, and other surprises depending what was cooked in it. A window screen or paint strainer will remove all the chunks big enough to cause problems in your reaction.
3 . Heat it up. There are several types of processors available to make or buy. Although my tank is made of plastic, it’s best to heat the oil in a metal container.  The reaction occurs best between 120F and 130F. If it’s colder, the reaction takes too long. If it’s hotter, you’ll boil off one of the chemicals involved in the reaction.
4.  Once the oil is up to 120F, you need to add lye and methanol. Both of these chemicals are dangerous if you don’t take proper precaution, so use common sense and safety procedures. Lye is the main component of powdered drain cleaners, methanol is a poisonous alcohol…don’t let either touch your skin and don’t breathe in the dust or vapors. There’s a specific formula for how to mix the lye and methanol, check out www.biodieselcommunity.org for all the details you could ever want.
5.  Drain the glycerin. Glycerin is the byproduct of the biodiesel reaction. It separates from the biodiesel and can be drained off the bottom of the barrel used for the reaction. It can be used to make soap, composted, or put into a methane digester. If you start making biodiesel, check with local regulations before you dispose of it down the drain
6. Wash it. The biodiesel is almost ready, but it has some leftover glycerin in it as well as some soaps that are formed as part of the reaction. These impurities are removed by putting a fine mist of water onto the biodiesel.  The tiny water droplets fall through the biodiesel and collect up the leftover glycerin and soaps. You know you’re done when the water is clear.
7.  Dry it. There is still some water suspended in the biodiesel. By “drying” the biodiesel, you allow this water to evaporate. Although there are several ways to do this, it’s easiest to just circulate the biodiesel with a pump that sprays it against the side of the tank. Air is blow into the tank with a small fan, which causes the suspended water to evaporate more quickly. After half a day, the biodiesel will no longer be cloudy.
8.  Filter it and use it. After a final trip through a filter, the biodiesel is ready for use in any unmodified diesel engine.

Although making biodiesel isn’t that hard, it’s not for everybody. Some people don’t have a spot to put a processor, don’t have time to do it, or just don’t want to deal with it…but there’s still hope. Biodiesel is becoming more and more available at gas stations around the country. There are also some cooperative groups that buy biodiesel in bulk and “sell” it to members of the coop.  Follow this link to Biodiesel.org to find biodieself fueling stations near you.  You can also try this one from FindBiodiesel.org.

Biodiesel is inherently more environmentally friendly than petroleum-based fuels because of its CO2 cycle. It can theoretically be “carbon neutral” and not contribute addition carbon to the atmosphere. This is because the oil producing plants take carbon from the atmosphere to produce the oil that is used to make biodiesel, rather than taking petroleum that has been “locked up” underground for thousands of years. This is reduced if petroleum fuel is used to transport the biodiesel or any of the components used to make it. As with all biofuels, you should consider the source of the “feedstock” for the fuel. It goes against the environmental benefits of using biodiesel if someone cut down rain forest to plant oil producing crops to make biodiesel…it’s a fair question to ask your suppliers. Biodiesel is obviously also more sustainable because it is made from a renewable resource (plants) while petroleum is a non-renewable, finite resource. To learn more about the environmental impacts of biodiesel, please see our full article on the topic.

Although biodiesel and other biofuels are a step in the right direction, we really need to consider why we use as much fuel as we do. A combination of taking fewer trips, using public transportation, riding bikes, and walking in addition to more efficient vehicles and biofuels is going to be necessary for a long-term sustainable approach to dealing with the world’s fuel consumption issues.

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