Making Fuel For Cars at Home

The Technology Behind Making Ethanol and Biodiesel at Home

Woman in field holding a beaker full of green liquid.
Ariel Skelley / Blend Images / Getty

While it’s possible to make both ethanol and biodiesel at home, and a lot of actual preppers either do so or have the equipment ready to do so if the worst happens, there are a lot of logistical, regulatory, and safety implications that you need to consider before you start production.

Whether you’re just looking for an alternative fuel, or you spend your days thinking about various apocalyptic scenarios, there are only two real options that work with the technology we already have in our cars and trucks. Ethanol is the primary non-petroleum stand-in for gasoline, and biodiesel is the alternative to petrodiesel that you can run in a diesel engine with little to no modifications needed.

It’s worth noting that you probably aren’t going to save any money making ethanol or biodiesel at home, versus buying gas or petrodiesel at a gas station, unless you have the feedstock available for free.

Before You Start

In terms of technology, making fuel at home requires a lot of knowledge, expertise, and potentially expensive feedstock, but the technology is pretty basic. Making fuel alcohol requires a still, and making biodiesel requires chemicals like methanol and lye, but no real technology to speak of aside from some method to test the final product.

The process of making ethanol at home is exactly the same as making moonshine liquor, so there are similar regulatory concerns. If you just set up a still in your backyard, especially if your operation is large enough to pump out any useful amount of ethanol fuel, you could end up in trouble with the feds. For instance, if you plan on producing more than 10,000 gallons of fuel alcohol in a calendar year in the United States, the Alcohol and Tobacco Tax and Trade Bureau requires you to obtain a bond.

Regardless of the amount of fuel alcohol you produce, you’re also required to denature it, or render it unfit for human consumption, by adding a substance such as kerosene or naphtha. This is what legally differentiates fuel alcohol from the kind of alcohol you drink, although it is sometimes possible to purify denatured alcohol via a similar process used to distil the alcohol in the first place.

The specific regulations for producing and denaturing fuel alcohol are available from the Alcohol and Tobacco Tax and Trade Bureau. Other countries have varying regulations or no regulations at all, so it’s important to check the local laws before starting a project like this.

The other main difference between distilling moonshine and fuel oil is that ethanol intended for fuel has to be a higher proof than most of the ethanol intended for human consumption. An appropriately low water content can be achieved through multiple distillation passes, but there are also filters that are capable of removing water content from fuel alcohol. In fact, some people who run ethanol in their vehicles use in-line filters to separate out water and gunk that the ethanol--which acts as a solvent--breaks loose from the fuel tank and lines.

Making Ethanol at Home

The specific process of making fuel oil is similar to making any kind of alcohol. It starts with a feedstock, which can be anything from corn and wheat (typically used to make bourbon), to switchgrass or Jerusalem artichokes. The feedstock is used to make a mash that ferments sugars and starches into alcohol, which is then passed through a still.

The most efficient way to produce fuel alcohol is to use a column still, as you may have to run 10 or more passes through a pot still to achieve a high enough proof. Not only is that energy inefficient, it also results in a greater loss of ethanol, as some is lost from each pass.

Obtaining Feedstock to Produce Fuel Alcohol at Home

The biggest issue with making fuel alcohol at home--either now or in some hypothetical, apocalyptic future--is feedstock. In order to create a mash that you can distill into fuel alcohol, you need some kind of grain or other plant material in great abundance. If you have a working farm, one possible option is to take corn or other grains that you have grown or harvested, use them to create a mash, and then use the leftover material to feed livestock.

The other option is to grow a crop specifically for use in the production of fuel alcohol. Corn is currently the main crop used for ethanol production in the United States, and each acre devoted to this use is capable of producing about 328 gallons of ethanol each year. Other crops, such as switchgrass, have the potential to be much more efficient. According to the U.S. Department of Energy, switchgrass yields have topped 500 gallons per acre, and ideal conditions could yield in excess of 1,000 gallons of ethanol per acre of switchgrass.

If you don’t have acreage to devote to cultivating corn, switchgrass, sugar beets, or anything else, then making fuel alcohol at home isn’t going to be a viable project.

Making Biodiesel at Home

First of all, it’s important to differentiate between cooking oil and biodiesel. Cooking oil, straight vegetable oil (SVO), waste vegetable oil (WVO) and similar, animal-derived products are all capable of powering a diesel engine, but they aren’t biodiesel. While cooking oil, SVO, and similar materials are simply collected and then used as fuel, biodiesel is altered to render it chemically similar to petrodiesel.

Although you can collect waste vegetable oil, or cooking oil, from local restaurants and run it in your car, you may need to modify your diesel engine to do so. Once the proper modifications have been done, the process of “making” fuel out of cooking oil is extremely simple. In order to render used cooking oil fit for use as a fuel, all you have to do is filter out the particulate matter.

Making biodiesel from SVO or WVO is more complicated, and it involves “cracking” the chemical structure of the fats or oils using methanol and lye. The process isn’t particularly difficult, but it is important to take necessary precautions, as both methanol and lye are toxic substances.

The process of making biodiesel from SVO, in very basic terms, starts out by heating the oil. Precise amounts of methanol and lye are then mixed together and added to the oil, which facilitates a chemical process known as transesterification. The result of this process is that you end up with two products: biodiesel and glycerine, which separates and settles to the bottom of the mixture. Finally, the biodiesel has to be washed and dried before it is ready for use.

Obtaining Feedstock to Produce Biodiesel at Home

The great thing about biodiesel is that you can make it out of a huge range of vegetable oils and animal fats, and you may even be able to obtain free feedstock from local restaurants. The process of obtaining the feedstock is as simple as contacting local restaurants, inquiring as to whether you can have their waste cooking oil, and then figuring out a way to transport it home.

Without a ready source of waste cooking oil, the subject of obtaining feedstock to make your own biodiesel becomes more complicated. While you can technically turn any kind of SVO into biodiesel, buying vegetable oil for this specific purpose isn’t cheap.

The other option is to make your own vegetable oil, which requires an appropriate press, but then you run into the issue of obtaining feedstock to create the oil—such as black oil sunflower seeds—which you would need to purchase or grow yourself. All of which is definitely possible, especially in a hypothetical zombie apocalypse or other SHTF type situation, after other resources are depleted. In the here and now, it's less economically feasible.