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Biodiesel – How to Process a Small Test Batch

In my three part series called Introduction to Biodiesel, I explained what biodiesel is, and how it is made, stored, and used. You can read it here:
Introduction to Biodiesel – Part 1
Introduction to Biodiesel – Part 2.
Introduction to Biodiesel – Part 3.

In this post, I will explain how I started out with experimental batches on a very small scale to learn the process. As we discussed before, you need a few things to get started: oil, methanol, catalyst, something to mix it in, and a way to heat it.

For the oil, I got some vegetable oil from the grocery store. By using brand new oil for the test batch, I knew it would not be acidic from cooking so I could eliminate the titration step. There would be time to learn that later. My focus for this test was to keep it basic and see the reaction work. So I bought a 48 ounce bottle of Wesson oil. That’s about 1420 ml so plenty for my 1000 ml test batch.

Unused Vegetable Oil

Unused Vegetable Oil

For the methanol, I got a bottle of HEET fuel treatment from an auto parts store. The one in the yellow bottle is methanol. Don’t get the red bottle which is called IsoHEET. It is isopropyl alcohol and won’t work. I use a 20% ratio of methanol to oil. The HEET bottle is 12 ounces, so that would be enough to react with 60 ounces of oil.

HEET (methanol)

HEET (methanol)

For the catalyst, I got some sodium hydroxide (NaOH) from Lowe’s. Later I would learn that potassium hydroxide is much better, but sodium hydroxide was more readily available. I wasn’t able to find lye at the grocery store. It turns out the government doesn’t believe we can clean our drains without harming ourselves, so it has been banned from grocery stores. I remember using lye as a kid to make hydrogen balloons – but that’s a story for another day. You can still find lye at a hardware store marketed as professional drain cleaner. You won’t need much but the smallest bottle I could find was $15. Just make sure it is labeled as 100% lye like the one in the picture. Anything other than pure NaOH won’t work.

Lye Drain Cleaner - Sodium Hydroxide

Lye Drain Cleaner – Sodium Hydroxide

I made the batch in a 2000 ml beaker using a hot plate with a magnetic stirrer. I skipped some steps that I described in earlier posts because this was just a test batch. There was no need to filter the oil or perform a titration because it was clean and unused. Remember to wear your protective gear during the next steps – gloves, safety glasses, and a respirator.

I mixed the methanol and sodium hydroxide in a 500 ml beaker using the magnetic stir plate. My test batch would be with 1 liter (1000 ml) of oil, so I used 200 ml of methanol based on the 20% ratio. There is some discussion about how much catalyst to use as a base amount – meaning how much you need to complete the reaction before adding extra to neutralize the acid based on the titration. I read a lot of web pages and settled on 5.5 grams of NaOH and 7 grams of KOH as my base amounts per liter of oil to be processed. You’ll need a scale for this step that is accurate enough to measure in .1 gram increments. These scales can be purchased online for under $15. I added 5.5 grams of NaOH to the 200 ml of methanol and stirred it until the NaOH was completely dissolved.

I poured 1000 ml of oil into the beaker, placed it on the hot plate, and started the heating process. The stirrer was used to heat the oil evenly. A thermometer allowed me to monitor the temperature. Once the temperature of the oil reached 130F, I slowly poured the methoxide in. I maintained the reaction temperature as closely as possible at 130F by manually adjusting the heat setting on the hot plate. Remember the reaction is exothermic, so it will take less heat to maintain the temperature once the reaction gets going. Be careful not to let the temperature get too high because it can boil off the methanol, causing the reaction to never complete. I continued the reaction for 30 minutes. For such a small test batch, it might not take that long but I figured it is better to run it a little longer than necessary rather than to cut it short and not complete the reaction. After 30 minutes, I turned off the heat and the stirrer and let it sit for a couple hours. It is important to note that I also skipped the step of testing the reaction for completion, but this biodiesel would certainly not be used in my vehicle.

The First Test Batch

The First Test Batch

The glycerin started settling to the bottom pretty fast. I let it sit and came back after a couple of hours. It looked like all of the glycerin had completely settled to the bottom.

Glycerin Settled to the Bottom

Glycerin Settled to the Bottom

That was it – the first test batch was done. I poured the biodiesel off into another beaker leaving the glycerin behind. Initially it was still liquid but by the next day it had solidified to the consistency of soft butter. The glycerin byproduct can be used to make soap. Glycerin from KOH stays liquid and can be used to make liquid soap. Out of curiosity, I mixed some of the glycerin with water and sure enough it lathered up like soap. Soap-making would be a great off-shoot project from biodiesel and a great fit for the self-sufficient homesteaders among us.

Gelled Glycerin from NaOH

Gelled Glycerin from NaOH

I subsequently made several more test batches the same way, including some with used oil, as I developed the testing methods. I kept that batch around for a while to remind myself of the significant accomplishment. Eventually I used it to start a fire outside. Even poor quality biodiesel is excellent fire starter so never throw away a bad batch.

Please join me to learn more in upcoming posts. I’ll talk about how to do the titration, methods of washing, finished product testing, and the processors I’ve built.

Please share your thoughts and opinions in the Comments.
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