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Introduction to Biodiesel – Part 2

In part one of this series, I explained what biodiesel is and the raw materials you need to make it. You can read it here: Introduction to Biodiesel – Part 1. In part two, I will explain in more detail how the process works and safety procedures you need to follow. Let’s get started.

The Process
The process consists of a few steps. I’ll get into detail about how the processors work in later posts. For now, here are the basics of the step-by-step process:

• Filter the oil: The oil is filtered to remove debris left over from the cooking process. I use 400 micron filters that are designed to fit on the top of a 5 gallon bucket. You can get them here: Bucket top filter. It takes a while for the oil to drip through these filters, so I start this step early – often the day before I’m going to process a batch.

• Titrate the oil: The cooking process increases the acidity of the oil. The catalyst is a base so some of it will be consumed by the acid in the oil. The titration is a test to determine how much catalyst will be required to neutralize the acid. If we don’t do this, some of the catalyst would be consumed to neutralize the acid and not enough would be left to carry out the reaction. It takes a certain amount of catalyst to carry out the reaction, which is easily calculated with a spreadsheet. We add extra catalyst based on the results of the titration.

• Heat the oil: The oil is heated to a target temperature of 130F. Heat is necessary for the reaction, but we don’t want it too hot. Methanol boils at 147F and that would mess up the process if we lost some of the methanol. For that reason, it is important to maintain the temperature fairly accurately during the reaction. Too low and the reaction might take longer. Too high and we can have a failed reaction. It is possible to control the temperature manually but automating the temperature control is a plus.

• Mix the methanol and catalyst: The results of the titration tell us how much catalyst to use. The volume of methanol is typically 20% of the volume of oil. There is some debate about the percentage of methanol varying between 15-25%. I had good results with 20% and have stuck with that. The catalyst is mixed into the methanol. It dissolves very slowly so this step takes a few minutes. It actually reacts with the methanol to form methoxide. The fumes should not be breathed, so wear a respirator during this process. I use a glass beaker with a magnetic stir bar on a stirring plate for this.

• Start the reaction: Once the oil reaches 130F, the methoxide is added slowly. The mixture is stirred continuously while the temperature is maintained at 130F during the reaction. It is an exothermic reaction, meaning it gives off heat, so maintaining the temperature requires less electricity once the reaction gets going. The reaction is complete when all of the oil is reacted. We have ways to test for that. Reaction time varies depending on the process you use. I will get into a lot more detail about the reaction and the processor in future posts.

• Separate the glycerin: Once the reaction is complete, the processor is turned off. Over the next several hours the glycerin will settle to the bottom, after which it can be drained off leaving only biodiesel in the processor tank.

• Wash the biodiesel: The remaining biodiesel is contaminated with excess methanol and catalyst, as well as some glycerin that doesn’t settle to the bottom. That all needs to be removed before the biodiesel can be used in your vehicle. There are several ways to remove the contaminants. Biodiesel can be washed with water or filtered mechanically. We have personally tested three different methods. We finally settled on a bubble washing method that I will describe in more detail later.

• Dry the biodiesel: The washing process leaves one last contaminant that must be removed – water. Heating the biodiesel removes the water. There are sophisticated tools for measuring water content, but generally it is dry enough to use if it is clear at room temperature. I heat in in one gallon beakers, then I allow it to cool. At that point it should look like iced tea. If it is cloudy, it is still wet. If it’s crystal clear, it is ready for the next step.

• Filter the biodiesel: The last step is to filter the biodiesel to remove any particles that might be left. I use a 1 micron bag filter. It is better to filter it out now rather than let your vehicle’s fuel filter catch it. One micron is smaller than the fuel filters used in vehicles, so anything that gets through this would get through your fuel filter too. After this step, the biodiesel is ready to be used.

If this seems complicated, it really isn’t. I’ll explain in much more detail how we do it in later posts. That will take all the mystery out of it. Rest assured, you want to learn to make it the right way. When I was first learning, I found this hilarious YouTube video where this lady put oil, methanol, and catalyst in a jug, shook it up, and let it sit in the sun for a couple days. Then she poured the “finished product” into her VW Beetle and drove off. I’m still waiting for the sequel where she’s calling a tow truck. Don’t do this! Learn to process it the right way.

Safety Precautions
Make no mistake about it. The biodiesel process is a chemical reaction. Safety equipment is important. If you’re careful and wear the proper protection, you shouldn’t have any problems. We’ll get into specifics when we talk about the process in detail, but here are some key safety hints:

• Eye protection: always wear it when working with the methanol and catalyst.

• Gloves: wear them when working with the methanol and catalyst. Methanol absorbs into your skin and the catalyst will burn.

• Respirator: wear a respirator when mixing the methoxide and later when adding it to the oil. When I process, I have a fan going for ventilation but a respirator is still necessary during these key steps.

• Fire Extinguishers: Biodiesel is flammable. So is methanol. I keep small fire extinguishers in several places in my workshop so one is always handy.

What’s next?
Learn more in the next part of this series: Introduction to Biodiesel – Part 3. I’ll explain in more detail how to store the finished biodiesel and how to use it.

Resources for this post:
Biodiesel Web Site: http://biodiesel.org/what-is-biodiesel/biodiesel-basics

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