How to Make Biodiesel

Traditional diesel fuel is made from petroleum, and in a post-apocalyptic world that will be hard to come by.  Thankfully, biodiesel is an alternative that can be made from any organic oil or fat that doesn’t require any kind of modification to your diesel engine.

Generally, you are adding a catalyst to a triglyceride-rich liquid in order to break a glycerin molecule off of the fatty acid chains in the oil and forcing each of three fatty acid chains to recombine with the introduced alcohol to essentially create a new alcohol.  This process is called transesterification.

Transesterification: ester + alcohol = different ester + different alcohol
Transesterification: ester + alcohol = different ester + different alcohol


Organic Oil/Fat

This can be nearly any kind of oil or fat (I’ve seen biodiesel made with rendered pig fat).  There are a few considerations to take into account though:

  • Peanut oil, coconut oil, palm oil, tallow, and lard all have a higher clouding point than other oils, meaning that they start to crystallize and gel at a higher temperature.  This means that they will work perfectly fine in warmer weather, but may cause problems in cooler temperatures.
  • Olive oil, peanut oil, palm oil, tallow, and lard have a higher acidity.  This can interfere with the transesterification process and means you probably want to titrate a sample (explained later) to determine if extra lye will be needed.
  • If you are using used oil, you need to process it before going forward with the recipe.

Rapeseed (or canola) oil, corn oil, soy oil, and sunflower oil are considered to be the preferable choice for biodiesel production.


It is possible to use either methyl alcohol or ethyl alcohol for biodiesel.  Methyl alcohol is preferable because there is less work involved with methyl alcohol.  Either way, you want as close to 100% pure as possible.


There are two types of lye potassium hydroxide (KOH) and sodium hydroxide (NaOH).  Either can be used, but KOH is preferable since it dissolves easier in alcohol.  Also, conveniently enough, it can be made per the instructions I give in How to Make Lye.


  • 10 parts oil
  • 2 parts methyl alcohol or 2.7 parts ethyl alcohol
  • 3.5 grams NaOH or 4.9 grams KOH per liter of oil used (plus any excess lye as indicated in titration for used oil)

The Process

Biodiesel and Glycerine separated into layers
Biodiesel and Glycerin separated into layers

Mix your alcohol and lye in an HDPE container (like a milk jug) and swirl occasionally until all the lye is fully dissolved.  This could take as little as 10 minutes for KOH and as much as overnight for NaOH.  This creates you methyl or ethyl esters.

Blend the ester mixture with oil/fat heated to 55C for roughly 30 minutes.

Let the mixture settle for 24 hours.  In this time, transesterification will occur, leaving behind glycerin as a by-product.  Three distinct layers will form, the heavy (bottom) layer is the glycerin, the light (top) layer is the biodiesel, and the middle layer is a soapy emulsion created by the reaction of lye with oil.  You can keep the glycerin, as it is useful in other situations, but unneeded for the rest of this recipe.  Move the biodiesel into a different container, ensuring that no glycerin or soap is carried along, and either store the glycerin or through it out.

Quality Testing

  • The Wash Test – Put a small amount of fuel in a PET bottle with water and shake vigorously for  approximately 10 seconds.  Let it sit for a half an hour.  If water separates from fuel with a very thin, foamy layer between (or no layer at all), then you’ve produced quality fuel.  If they don’t separate or there is a thick foamy layer, then your fuel is of poor quality.  This can be caused by too much lye or contaminants present acting as emulsifier.
  • The Methanol Test – Mix 25ml of biodiesel with 225ml of methanol.  If anything is going to separate, it will happen nearly instantly.  Each milliliter of biodiesel that separates from the methanol equals a 4% impurity.  Ideally, nothing will separate, meaning your fuel is 100% pure, but a little bit won’t hurt.


After testing to ensure your fuel is good you need to “wash” it.  This process removes any physical impurities or unconverted ingredients from the fuel, as these can all cause problems in your engine down the line (lye can corrode the fuel injectors and fuel tank, glycerin and soap can clog any number of parts, etc).  Mix 1 part fresh, clean water with 2 parts biodiesel until it appears homogenous.  Let the mixture settle for several hours, then drain water.  Move fuel to new receptacle and repeat process 2-3 times.  Let the fuel sit for several days. once it is no longer cloudy, it is “dry” and ready to use.  If it doesn’t clear up, you can try washing it again.

Processing Used Oil

You can use “certified pre-owned” oil to make biodiesel, you just need to do some things to it first.

Cleaning Old Oil

Some people recommend filtering the used oil first, but I say that it is unnecessary.  All the gunk and goo in the old oil will sink to the bottom and since you are usually working with the top layer of a separated liquid, you are naturally filtering it as you work with it.  However, there is a significant amount of water suspended in used oil (typically from the food cooked in it) and that can be a problem.

To remove the water, bring the oil to a boil at 100C and leave there until boiling slows, then boil at 130C for approximately 10 minutes.  This should ensure that most of the water is removed.


Every time you use or heat oil you create free fatty acids, which are basically broken-down triglycerides.  This means that there is more work required to convert your oil into biodiesel than with new oil.  This work is done by adding extra lye to the process.  To find out how much more lye to add, we use a process called titration.  This process should also be used if you are using ethyl alcohol instead of methyl alcohol, or an oil with a higher acidity.

First, make a 0.1% lye solution by mixing 1g of lye into 1 liter of distilled water.  Now dissolve 1ml of oil in 10ml of isopropyl alcohol.  At this point you need to choose a way to determine the pH of the oil/alcohol mixture.  You can use a pH tester, phenolphthalein droplets, or (if push comes to shove) red cabbage juice – seriously it indicates pH really well..  Add the lye solution drop by drop until pH is around 8-9.  If you’re using phenolphthalein, this is indicated by the liquid turning a pinkish color, if you are using red cabbage juice you are looking for a blue/blue-green color.  The number of milliliters of lye solution added to the oil solution equals the additional number of grams of lye per liter of oil to use in the transesterification process.


If you want to get super technical in your measurements, the amount of KOH used depends on the strength.

Purity Measurement (in grams)
99% 4.9
92% 5.3
90% 5.5
85% 5.8

Red Cabbage Juice

pH 2 4 6 8 10 12
Color Red Purple Violet Blue Blue-Green Greenish Yellow

How to Distill Alcohol, part 3: How to Make Methanol

[error]DISCLAIMER: The following is highly dangerous or illegal and it is not recommended to be used under any circumstances, except zombies.[/error]

Methanol, or methyl alcohol, can be used primarily as a fuel source or feedstock (a chemical used to make another chemical).  For our purposes, we can either use it to fuel cars, trucks generators, etc. or to create biodiesel (both very useful in a post-Apocalyptic world).  In this part of our series on alcohol distillation, we discuss how to use your still to produce methanol.

Methanol is more commonly referred to as wood alcohol because, until breakthroughs in modern chemistry, the only way to produce it was by extracting it from wood.  You shouldn’t drink methanol EVER.  Not only does it taste bad, but it can kill you.  In fact, methanol is used to denature ethanol products, rendering them undrinkable by making you violently ill when you drink even that small of an amount.  If you want to make drinkable alcohol read about it here.

Producing methanol is a much less involved process than producing ethanol.  Put wood chunks or shavings (or paper) into the bottom of your cooking vessel and add enough water to cover the wood.  Heat the cooking vessel to around 78C and wait as the methanol vaporizes from the wood and out the condenser coil and into your storage container.

If you are making both ethanol and methanol make sure you label them.  I can’t stress to you how important it is that you don’t drink methanol.

How to Distill Alcohol, Part 2: How to Make Ethanol

[error]DISCLAIMER: The following is highly dangerous or illegal and it is not recommended to be used under any circumstances, except zombies.[/error]

In Part 1 of this article series, I showed you how to make your still.  In this part, we go over the specfics of how to make actual ethanol, or ethyl alcohol.

Ethanol is most commonly known for being the ingestable alcohol in liquor, but there are plenty of uses for it aside from drinking.  First and foremost, everybody likes alcohol, so if you can make your own, you have a valuable commodity to trade with other people.  Beyond that, it is a disinfectant, an antiseptic, a solvent, it is flammable so it can be used as a fire source or a fuel source, and interestingly enough – it can be used to treat alcohol poisoning from other, more toxic, types of alcohol.


Fundamentally, all that distillation does is seperate the alcohol from everything else.  So in order to distill ethanol, we need to create something that contains ethanol.  You need to create a mash using some sort of starchy substance.  Pretty much any type of grain will do, corn is a good starch source and is probably the most prolific option.  Rice will also work, but may be in short supply.  The fermentation process for distilling alcohol is very similar to that of making beer but has more leeway, since you don’t really care about the flavor that the mash itself develops.

Your first step is to heat up a volume of water at a ratio of 3 liters of water to 1 kilogram of starch source to around 65-70C.  Add your starch source to the water and maintain temperature for around an hour or so.  Larger quantities will take longer to get to temperature and longer to drop temperature, it’s not unheard of for home distillers to let the mash sit for days before proceeding.  What this does is convert the starches in your starch source into fermentable sugars (mono- and disaccharides).  Let it cool to a temperature no greater than 27C (the maximum tolerable temperature for most yeast) then add 0.5kg of yeast per 200 liters of mash.  You can also add table sugar at this time to aid in fermentation, but it isn’t terribly necessary.  Let the mash sit for around 10 days to ferment.  A rough indicator that fermentation is done is when the mash stops bubbling.  Fermentation continues passed this point, but unless you have equipment like a hydrometer available to test the specific gravity of the mash, no bubbles is a good enough indicator.


First, let me clue you in on how dangerous this part of the procedure is.  You are playing with alcohol, a highly flammable substance, over an open flame.  If there is a leak anywhere in your system, it will literally go up in flames.  Which means you could just as easily go up in flames.  Add the fact that you are working with a closed system, you are essentially pressure cooking a flammable substance.  If your system isn’t balanced properly, pressure will build up inside your cooking vessel and eventually cause it to explode.  You are basically standing next to a bomb for several hours, if not days.  Be vigilant or your still could rain fiery death on you at incredible rates of speed.

If you didn’t ferment your mash in your cooking vessel, place it there now.  Bring your mash up to a temperature of around 79C and maintain tht temperature for the remainder of the process.  As described in part 1, you are keeping a temperature that allows the ethanol to vaporize without any of the rest of the mash vaporizing as well (for the most part).  The alcohol vapor then escapes through the condenser and is cooled down to liquid form before exiting into your storage container.  If you intend any of this to be drank, you’ll want to seperate the first few ounces from the rest of it because this first bit generally contains all kinds of impurities and all-around nastiness.

That’s it!  That’s how to make ethanol.  It’s a ridiculously simple method, but incredibly dangerous if you aren’t paying attention.

How to Siphon Gasoline

Whether it be for a generator or a vehicle, at some point your quality of life will be greatly improved by having access to gasoline. But where do you get it? There might be some in the underground tanks at a filling station, but this tends to be a bit more difficult to access. There might be some in abandoned vehicles on the side of the road. But how do you get it out of either container? It’s likely that you don’t have an electric pump to extract the fuel and it’s unlikely that the filling station will have power to operate the pumps. Enter the siphon. 

How a Siphon Works

A siphon is a very simple tool used as far back as the ancient Egyptians. The premise is that you use a tube to move liquid from one container to another. The tube you use is placed in a U shape with each end of the tube facing downward into each of the recepticles (the longer end of the tube being placed in the receiving vessel). There should be liquid in the tube at this point and when let free to do what it will, the liquid will begin to flow into your receiving vessel. This is due to our old friend gravity. Look at the tube, the longer leg of the tube has more liquid in it, thus more mass, and therefore gravity exerts a stronger force on it, causing it to fall into your receiving container. Gravity gets this party going, but dynamic fluid pressure is what keeps it going. Dynamic fluid pressure is the pressure exerted by a moving fluid. Since the liquid falling into the receiving container is exerting a higher dynamic pressure (greater gravitational acceleration and eventually greater velocity = greater pressure), it causes the liquid in the other leg to follow it. Now the liquid from the shorter leg is in the longer leg free falling into the receiving container, which in turn cause liquid in the source container to flow into the tube for the same reason. This creates a cycle that will only be broken when the source recepticle is empty or cavitation occurs (this isn’t likely in this scenario so I won’t even explain it). 

How to Siphon Gasoline from a Car

Applying the principles discussed, siphoning gasoline from a vehicle should be no problem. Place on end of your hose into the fuel tank via the refueling hole on the vehicle. Make sure to feed it as far in as possible. Place the receiving container lower than the fuel tank of the vehicle. At this point you have 2 choices on how to prime the siphon. You can either create a vacuum by sucking the first bit of fuel through the hose, or you can fill the hose with water. I highly recommend sucking gasoline from the tank even though you may end up with a mouthful of it (not a pleasant sensation, trust me) because water can ruin the gasoline, causing the fuel to oxidize much faster than normal. Either way, once your priming liquid reaches a point lower than your fuel tank, you should be able to drop it in your container and watch the fuel flow!

Stale Gasoline

Yes, there is such a thing as stale gasoline. But is it that serious of a problem? Yes and No. Gasoline can be considered “stale” very shortly after processing. This is because the more volatile chemicals in gasoline will have evaporated and decomposed. These compounds improve combustion and improve fuel efficiency, so if they aren’t present it’s not the end of the world, it just means your fuel economy is downgraded. That’s the part we don’t really care about, fuel is fuel and whether you lose a few miles per gallon or not is not a concern. 

The big concern is oxidation. If the fuel you collect is oxidized this can cause much bigger problems. You can tell if the gasoline has begun to oxidize because it will have a particularly sour smell and will be a darker color than normal. Once it begins to oxidizes, gasoline will start to have particles of a gummy substance that can cause a build up in your fuel system, which can cause your engine to cease working. You could try to filter these particles out, but its a lot of work for something that only may work. 

You also have to worry about water contamination. Getting water in your fuel can cause a decrease in performance and, at worst, can cause your fuel lines to freeze and potentially burst. There is a simple solution: add isopropyl alcohol to your fuel. Simple rubbing alcohol will bind with water molecules to create a combustible compound which will then burn off in the engine. 

Further Reading