Biodiesel FAQ

Here are some of the most frequently asked questions we’ve encountered about biodiesel. If you don’t see the answer to your question listed here, contact us and we’ll get an answer for you.

>> BioDiesel 101
>> Safety and the Environment
>> Energy Cost and Use

>> Making BioDiesel

BioDiesel 101

>> Where can I learn more about biodiesel in general?

A great resource is the book From the Fryer to the Fuel Tank by Joshua Tickell. You can purchase it online at Another good source is the National Biodiesel Board at

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Safety and the Environment

>> How safe is biodiesel to handle? What about spills?

Biodiesel is non-toxic, fully biodegradable, and safer to store than petroleum diesel.

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Energy Cost & Use

>> Am I responsible to pay fuel tax? If so, how much and how do I pay it?

Technically, you are responsible for paying any applicable “road use” taxes on the biodiesel you make. The IRS provides a 1,600 gallon/person/year exemption for home-made and personally consumed (not sold) alternative fuels like biodiesel.

>> What size processor do I need?

It’s based on supply and storage logistics. Our processor assumes you’re working with 1 barrel of oil and 1 barrel for biodiesel storage/delivery for every batch you make.

>> Will my biodiesel void my diesel engine’s warranty?

Most major diesel vehicle manufacturers have already acknowledged that up to 5% (B5) biodiesel will NOT void your warranty. Check with your dealer or diesel mechanic for further details. Companies such as Cummins, Caterpillar and John Deere have extensively tested biodiesel and are strong supporters.

>> Are there any modifications required in my diesel vehicle to use my biodiesel?

In most cases you can start using biodiesel immediately without any modification. The only exception is older (pre-1990 diesels) may have natural rubber fuel lines which are susceptible to slow degradation with biodiesel. Just replace these with current synthetic fuel lines and you’re done. You should also replace your fuel filter after your first tank of biodiesel, since biodiesel is a very good solvent and will scrub out all of the tars, varnishes and gums left by petroleum diesel in your fuel system.

>> How do the costs break down in making my own biodiesel?

Racing Methanol is $2.50 per gallon, but you only use 1/5 gallon for every gallon of biodiesel you make. Lye costs about $5 per pound, and a 40-gallon batch will need 1.5 pounds. Used cooking oil is generally free from local restaurants. Your time is calculated as you would a hobby-free. That adds up to $0.50 + $0.20 = $0.70 per gallon!

>> Can I use my biodiesel for other diesel-fueled devices, such as home heating oil furnaces?

Biodiesel can be safely used in ANY device which can use #2 diesel fuel. That includes cars, trucks, tractors, generators, pumps, heaters and home furnaces. Check with your equipment service technician, or carefully start feeding your equipment ever greater percentages of biodiesel and carefully monitor the performance.

>> Can I use biodiesel in colder climates?

Biodiesel does “gel” at a somewhat higher temperature (about 35-40F) than petroleum diesel (25-30F). To lower the gel point of biodiesel you can a) mix it with some “winterized” (contains some thinner #1 diesel); b) add an “anti-gel” additive specifically formulated for biodiesel; or c) install a fuel system heating kit and run 100% biodiesel well below zero.

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Making BioDiesel

>> What are good or bad places to locate my processor?

Find a sheltered, secure and well-ventilated spot out of the flow of traffic and away from ignition sources and combustibles. It’s a good idea to have a floor suitable for rolling barrels like methanol and biodiesel around, so you can store them in a safe place away from the processor.

>> Can I use potassium hydroxide instead of sodium hydroxide?

Yes, but you’ll need more of it and it’s more expensive per pound. And it isn’t always as strong a catalyst as lye.

>> How long can I store biodiesel?

Biodiesel can be stored for years provided that it is kept free of oxygen (displace air with dry nitrogen from your local welding shop) and bacteriological growths (just add a biocide made exclusively for biodiesel).

>> How can I tell whether the oil I plan to use is suitable for making biodiesel?

The two most important factors are water content and Free-Fatty Acids (FFA) from animal fats or over-use of oil. Water content used fryer oil can be checked for water content (bad) by simply boiling a sample of oil in a frying pan and looking for bubbles from the evaporating water. Acid content can be checked first by simply asking what’s been cooked in the oil, then doing a simple pH test (by titration) to see how heavily used it is.

>> Where can I get lye and methanol?

You can find lye in your hardware store plumbing aisle under the drain cleaner marketed as Red Devil, or contact soap making supply houses. Methanol can be bought from racing fuel dealers and fuel distribution centers.

>> Is there a simple way to purify the raw glycerin to the point where it becomes marketable?

Not really. You have to raise the temperature VERY high, and perform special processes to get market-grade (95% pure) glycerin.

>> Is there a hierarchy of preference for used vegetable oil?

Yes, oil which has been used to cook: 1) only vegetables (fries, tempura, etc.); 2) fish; 3) chicken; 4) beef and pork. Avoid oils mixed with hard, tallow, grille scrapings, or any other waste animal fat.

>> Can I use ethanol instead of methanol?

Yes, but you’ll need more of it and it’s more expensive per gallon. The main difficulty with ethanol is that it is VERY hard to get and keep “water-free” enough to achieve a good reaction.

>> Will I attract the attention of the DEA or BATF by procuring methanol or lye?

If asked, tell them you are making your own safe, environmentally-friendly biodegradable fuel called biodiesel.

>> Can I mix my biodiesel with regular petroleum diesel?

You can mix biodiesel in ANY ratio, back and forth, with no problems.

>> Why does each batch require a different amount of chemicals (titration)?

Different used oils will have a different amount of Free Fatty Acids (FFAs) in them based on how extensively they’re used. These acids must be neutralized, and additional catalyst must be added to make the biodiesel reaction happen. It’s an easy test, but a very important one to get the best results.

>> What are the regulations regarding storing methanol and biodiesel?

If you treat your barrels of methanol and biodiesel as you would treat barrels of gasoline you’ll be safe. Check with your local fire marshal about your local safety regulations for storing gasoline (such as using it to run an emergency generator).

>> How much will I have to pay for used cooking oil?

In most cases a restaurant will be happy to simply give you their used oil, since they would otherwise have to pay to dispose of it. Just be clean, safe and responsible when you pick up oil.

>> What happens when all the free used oil is gobbled up by others?

First of all there are over 3 Billion gallons of used cooking oil produced EVERY YEAR in the US alone. But beyond that, there are many other non-food grade oils coming on the market that are cheap and suitable for biodiesel.

>> How do I get rid of all the glycerin I’ll be accumulating from making biodiesel?

You have several choices: 1) evaporate the methanol and compost the rest; 2) recover the methanol and compost the rest; 3) recover the methanol and purify the glycerin, then compost the rest; 4) mix 50/50 with water and use it as a shop cleaner and degreaser.

>> Is there a simple way to recover some of the methanol used in the process?

You can use a close-top cooker with a condenser to collect boiled methanol. Recovery is about 20% of what you used in your last batch of biodiesel. Realize that glycerin becomes very thick and gelatinous when the methanol is removed.

>> What can go wrong in making biodiesel?

Two most common mistakes are: a) using the wrong amount of lye, and b) excessive agitating of the water during the biodiesel wash cycle. Both of these mistakes can be easily avoided by carefully following the detailed instructions with the unit you’ve purchased.

>> Do I always have to wash my biodiesel, and how much?

Although you can use unwashed biodiesel in a pinch, we recommend you always wash your biodiesel until the wash water is only slightly murky after hours of washing. The pH should be less than 8.0 which indicates a clean and pH neutral biodiesel.

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