Most of us are at least vaguely familiar with biodiesel, but how much do we really know?

While biodiesel is easily the most popular alternative fuel available, it’s commonly misunderstood or misrepresented by inaccurate information. Since the most frequent question I get is, “So what exactly is biodiesel, anyway?“, I decided to write a tome covering all the basics—a one stop shop for all your biodiesel- related questions.

It’s been exactly one year since I published the first Biodiesel Mythbuster on, and its popularity made a sequel inevitable. By way of a short introduction, here’s what I wrote last year:

In case you’re new to the topic, biodiesel is a renewable fuel made from plant oils and occasionally animal fat. It can be made from both used and unused sources of oil, such as freshly-pressed soybean oil, or oil left-over from the deep fryer at your local burger joint. Biodiesel can only be used in diesel engines – no gasoline engines allowed. Biodiesel can be blended into regular diesel in any amount, such as 20% biodiesel/80% diesel (B20), or used pure 100% (B100, aka ‘neat’). As a disclaimer, this post does not address homemade biodiesel (aka homebrew), which usually does not meet the quality standards of ASTM-certified biodiesel.

Here is the new and improved Biodiesel Mythbuster 2.0:

MYTH #1: Biodiesel and Ethanol are the same thing.

FACT: This is the most commonly held misconception about these two fuels, but ethanol and biodiesel are, in fact, completely different. Ethanol is the product of fermentation (think: SUGAR), and biodiesel is chemically-converted fat or oil (think: PLANT OIL).

  • Ethanol is made from a sugar source like sugarcane in Brazil, or corn-grain in the US. In the second example, corn is ground and mixed with water to form a slurry, and treated with enzymes to break down complex sugars (dextrose) into simple sugars (sucrose). The slurry-mash is then transferred to a fermentation vat where yeast are added. The yeast turns the simple sugars (sucrose) into carbon dioxide and ethanol. You may recognize this process, because it’s the same way moonshine is made.
  • Ethanol can also be made from more complex plant material containing cellulose—aka cellulosic ethanol—a process that is still being developed. The first major commercial cellulosic ethanol facility will go online in 2009. Some studies have shown that cellulosic ethanol has the potential to displace around 30% of US gasoline usage with major reductions in greenhouse-gas emissions.
  • Ethanol is blended into gasoline. Half the gasoline in the United States is already blended with 10% ethanol. It was commonly thought that higher blends would damage standard gas engines, but a recent study discovered that most cars can run on 20% ethanol with no problems. Ethanol is usually sold in as E10 (10% ethanol, 90% gasoline) or E85 (85% ethanol, 15% gasoline). Only Flex-Fuel vehicles can run on E85.
  • Biodiesel can be made from any plant oil or animal fat. Some examples include soybean, rapeseed, and palm kernel oils, and also animal fat left over from meat processing (disgusting I know). Biodiesel can also be made from recycled restaurant cooking-oil, often called waste-vegetable-oil (WVO), and is a major feedstock for some biodiesel producers.
  • Biodiesel is most commonly made by mixing plant oils with lye (sodium hydroxide, or NaOH) and methanol (CH3COH). This splits up the fat molecules in the oil leaving a less-viscous biodiesel and one waste product: glycerol.
  • The dream feedstock for large-scale biodiesel production has been biodiesel from algae, a nonfood source of oil with incredible yields. The first algae-to-biofuels plant went online April 1st, 2008.
  • Biodiesel can be blended into diesel fuel in any amount, but the most common blends are B5 (5% biodiesel, 95% diesel), B20 (20% biodiesel, 80% diesel), and B100 (100% biodiesel).

So, just to recap, biodiesel is chemically processed fat or oil for use in diesel engines and ethanol is basically moonshine that can be added to gasoline.

MYTH #2: Ethanol is better than biodiesel (or vice versa).

FACT: If you read the news, you probably think biofuels are generally bad, with corn-grain ethanol being the worst of the bunch. But as usual, generalizations fail here, since every biofuel is unique in terms of manufacturing process and environmental impacts.

Corn-grain ethanol and Malaysian palm biodiesel have substantive negative impacts (like deforestation, waterway pollution) and questionable benefits. But they are completely different than US-grown soybean biodiesel or second-generation biofuels that aren’t based on food-sources—like algae biodiesel.  They are simply a part of the larger solution.

Here are some of the latest headlines on non-food based fuel:

MYTH #3: Biodiesel (and other biofuels) are a total waste of time; they’ll never solve anything.

Fact: This is a totally bogus argument. Here’s why: there isn’t a solution for our petroleum addiction. If you dismiss biofuels as a fantasy-land panacea, you’re right, because it’s going to take a combination of improved fuel economy, massive reinvestment in public transportation, new technology, new fuel sources like non-food based biofuels and electricity, and other factors to move us into transportation 2.0.

As they say, don’t make perfect the enemy of the good.

Biodiesel has already had major impacts in offsetting diesel fuel usage and reducing pollution, impacts that could not be realized if we just gave up on it because it will never meet our total fuel demand.

For example, biodiesel made from waste cooking oil that would otherwise be discarded or shipped to China for processing is displacing 1 million gallons of diesel fuel in Oregon each year. In total, 450 million gallons of biodiesel was produced in the United States in 2007, amounting to an emissions reduction of approximately 1,102,399,500 lbs. of carbon dioxide*.

(*My estimation assuming all soybean biodiesel, based on 40% lifecycle GHG reduction and 6 lbs of CO2 per gallon of diesel fuel).

MYTH #4: You must convert your vehicle to run biodiesel.

FACT: Let me describe the conversion process (which is also outlined under 6 Ways To Find And Use Biodiesel Anywhere): Drive to the nearest biodiesel pump, put the spout in the side of the car, and pump the biodiesel into your fuel tank (provided it’s a diesel). That’s it. You can use biodiesel in almost any diesel engine without modification. In fact, if you own a diesel vehicle you can probably fill it up today with 100% biodiesel (B100) and should experience no problems whatsoever.

That being said, there are two major exceptions for newer vehicles: if you’re worried about voiding your warranty, or if your car’s operating manual specifically prohibits using biodiesel. I’ll deal with warranty issues further down the page, but let me say here that I’ve only heard of one manufacturer explicitly prohibiting biodiesel use in a new diesel, and that’s Audi’s A3. Presumably this has something to do with the intense pressures and precise fuel injection parameters of newer engines, but VW still warranties B5 biodiesel in their brand new 2009 Clean Diesel Jetta TDI.

But for users where those two exceptions don’t apply, let me repeat this: you can use ANY amount of biodiesel (see cold weather considerations below), from B2 to B100, in a diesel engine with NO immediate or necessary modification to the engine.

Reasoning for this myth is based biodiesel’s solvent properties: over time it can degrade natural rubber, and it will clean out diesel sludge that has accumulated in older fuel lines. The second one is actually a good thing, but if you drive an old diesel vehicle, it’s a good idea to change your fuel filter after a tank or two of biodiesel, or your fuel filter could subsequently clog. I’ve only heard of this happening a few times, and it can be easily avoided by switching out the fuel filter yourself (get the filter at Napa or Autozone) or take it to Jiffy Lube.

As for natural rubber, it’s uncommon in post-1990 vehicles. Depending on the age of your car, you may need to swap out the rubber fuel lines and replace them with synthetic Viton hosing. But don’t lose any sleep over this. It only takes a few minutes, and if you can’t figure it out a mechanic should be able to do it in 15 minutes. You may not even need to change them out. The rubber fuel lines in my 25-year-old Datsun pickup truck did just fine when I switched to B100, and didn’t need replacement during the two years I owned it. For an excellent (if slightly technical) example of what the swap looks like, check out this post from the NissanDiesel Forums.

MYTH #5: You have to be a diesel mechanic to use biodiesel.

FACT: No, all you have to do fill up with a different fuel, just like switching between regular and premium. The ‘conversions’ mentioned above are easy, take minimal mechanical skill (being able to use a screwdriver), and shouldn’t take more than an hour. When I bought my first diesel, I’d never even changed the oil in a car, and I haven’t used petro-diesel since.

MYTH #6: Biodiesel will wreck your engine.

FACT: Nope. This is completely false. There have been reports of biodiesel damaging gasoline engines (just like diesel would), and I’ve heard that’s why some mechanics rail against using the fuel—they’ve had to deal with these hapless folks. While original engine manufacturers (OEMs) are especially cautious about new fuels, some of biggest names in the diesel world (like Cummins, Caterpillar, John Deere, and others) have cleared B20 or higher from doing any harm.

Biodiesel and diesel fuel are similar in chemical structure and have similar properties, so they burn similarly in diesel engines. But biodiesel has some specific advantages. Biodiesel adds significant lubricity to the fuel (something that sulfur formally did in diesel fuel, but has since been reduced, hence ultra-low-sulfur-diesel or ULSD), reducing engine and fuel pump wear and reportedly extending engine life. Adding just 1% biodiesel to ULSD will restore lubricity to the fuel.

Biodiesel has a higher cetane number (higher ignitability) and combusts more completely due to higher oxygen content. Biodiesel is also a good solvent and will clean out diesel fuel residue left in the fuel tank and lines. Over time, because it’s such a good solvent, biodiesel can degrade rubber fuel lines and gaskets. Most post-1990 vehicles don’t have rubber lines and gaskets, but some older vehicles do.

MYTH #7: Biodiesel will cause a noticeable power decrease.

FACT: Biodiesel contains about 8.5% less energy per gallon than petroleum diesel. For someone using B20, this means about a 1-2% loss in power, torque, and fuel efficiency. To put things into perspective, that’s about a 2 mph difference on the freeway if you were trying to go 55 mph. Millions of miles of onroad tests (aka trucking) have shown that B20 and diesel are practically indistinguishable. Biodiesel has also been used extensively in heavy-machinery, like tractors, loaders, and agricultural equipment, with no noticeable difference.

B100 users may notice a slight drop in fuel mileage based on the small difference in energy content, but torque and power are usually comparable. I’ve seen a 1-3 mpg drop in fuel efficiency running B100. As an FYI, biodiesel has the highest BTU (energy) content of any alternative fuel (falling somewhere between diesel #1 and #2). Energy content of various fuels (per gallon, low value of range):

  • Regular Diesel Fuel = 128,500 BTUs
  • Gasoline = 125,071 BTUs
  • Biodiesel = 118,296 BTUs
  • Ethanol = 76,000 BTUs

MYTH #8: Biodiesel use will void your warranty.

FACT: This myth is a little more problematic because it’s partially true. While all manufacturers have approached biodiesel cautiously, many now recognize and warranty B20 for use in new vehicles. See the table listing biodiesel manufacturer warranty information.

However, things get a little more complicated when you start to argue that the use of a fuel cannot void non-fuel system warranties. According to the National Biodiesel Board (NBB), “The use of biodiesel in existing diesel engines does not void parts and materials workmanship warranties of any major US engine manufacturer.”

Apparently, Federal law prohibits the voiding of a warranty just because biodiesel was used—it must be the cause of the damage, though some manufacturers will assume biodiesel caused the problem. Warranties generally don’t cover problems caused by external sources, i.e. bad fuel, but can’t be voided if the problem was unrelated (see NREL’s Biodiesel Handling and Use Guidelines, p. 47). Most manufacturers do support B5 or B20, but that doesn’t mean they necessarily prohibit higher blends.

The best thing you can do: double-check with your manufacturer!

Of course, for those of us who have never had a car warranty, no sweat! Don’t lose any sleep over this!

Update: Biodiesel’s New Approval Rating Could Ease Warranty Concerns

MYTH #9: Biodiesel doesn’t work in cold weather.

FACT: Alright, this is another potential stumbling-block, but a manageable one. Perhaps you’ve read my personal experience with biodiesel in cold weather—let me reiterate that operator error led to the breakdown. It’s true that biodiesel clouds up (starts to freeze) at higher temperatures when compared to regular diesel, and therefore it’s important to blend biodiesel with diesel fuel in the winter (depending on your climate). Here are the biodiesel cold-weather guidelines unless proper cold weather additives are use:

  • B100 can be used down to about 40 degrees F
  • B50 between 20-40 degrees F
  • B20 below 20 degrees F

Remember that the cold-flow properties (as they’re called) vary depending on what the biodiesel is made from (feedstocks with more saturated fat, like coconut oil or animal parts tend to freeze earlier). Local producers should be able to give you more information about this, though most biodiesel you will find is going to be soy biodiesel.

When I lived in the Pacific Northwest’s rather mild (in terms of temp) climate, I typically used B100 between March and November, then switched to B50 for the winter, unless I planned on hitting much colder temperatures (I mean anything approaching 0 F). I’m aware of people using B100 all year round in Corvallis, Oregon, with no problems.

By the way, if you end up using the wrong blend, or get caught in a cold snap, it isn’t the end of the world. Your engine will shut off when the fuel filter clogs from partially-gelled biodiesel. This doesn’t cause any permanent damage, but you will have to wait for a sunny day or apply some serious heat to get things running again. (After stalling out on the freeway once in 13 degrees F and being towed to a gas station, I had to fill the empty space in the fuel tank with diesel, add an anti-gelling additive (available at any gas station), replace the fuel filter, and wait for a sunny day).

The cold-weather problem is not insurmountable, made clear by biodiesel use in snow-cats at some ski areas. All you have to do is heat the fuel system, from fuel tank to injection pump, which is precisely the same thing you do to convert a diesel to run on straight-vegetable-oil. For more information and some ideas, check out the cold-weather fuel products from Arctic Fox.

MYTH #10: Biodiesel has no quality control; you could be buying anything.

FACT: While there’s definitely room to question the consistency of biodiesel quality control (see earlier post), the industry has strict guidelines in place. Biodiesel has it’s own fuel standard, ASTM D-6751, which determines whether or not a substance is actually biodiesel. The National Biodiesel Board also set up the BQ-9000 quality certification program to create a nationally-recognized list of approved distributors.

I personally wouldn’t worry about the quality of biodiesel at the pump, considering the scant attention regular petro-diesel quality receives.

Quality control can be a major issue, however, if you’re using homebrew biodiesel or biodiesel purchased from a biodiesel coop. If you choose the latter, make sure they test their fuel periodically to see how close they get to D-ASTM 6751.

MYTH #11: Biodiesel is impossible to find.

FACT: Many people assume this without actually looking, but biodiesel could be readily available in your area. That’s why I wrote 6 Ways To Find And Use Biodiesel Anywhere. Check it out. It will tell you how to find retail biodiesel stations, how to map them on Mapquest, and how to get emergency biodiesel locations on your cell phone. Biodiesel is the most widely available renewable fuel and can be found in many major metropolitan areas.

MYTH #12: Biodiesel use requires a new fuel infrastructure.

FACT: One of the key benefits to using biodiesel is its seamless integration into existing infrastructure (unlike ethanol, which has water-collection issues). Biodiesel can be transported and stored anywhere that petroleum diesel can, and can be dispensed from the same refueling equipment.

MYTH #13: Biodiesel is too expensive.

FACT: Last time I checked, biodiesel was $3.30 per gallon.

Unfortunately, biodiesel is tied to petroleum prices because of complicated issues related to the web of factors influencing commodities pricing. But in areas where biodiesel is made from non-food sources, and looking to the future when we hope all of it is made from non-food sources, biodiesel can be cheaper. Sequential Biofuels of Oregon makes biodiesel out of 1 million gallons of recycled vegetable oil each year. In any case, biodiesel isn’t any more expensive than diesel fuel, and in some places it can be significantly cheaper (Pacifica, Ca: $3.23/gallon on 6.17.2008).

That being said, we could probably argue about the real price of petroleum for hours. Americans don’t see the real price of petro-diesel at the pump, which should probably include the cost of climate change (in the form of a carbon tax) and some of the most expensive aspects of US foreign policy (I’ll let you fill in the blank). It also doesn’t include the health care and societal cost of the estimated 15,000 premature deaths attributed to diesel exhaust each year.

The US will export an estimated $440 billion dollars (update: I think it’s twice that now) in 2008 to satiate its oil demand, which represents something like half of the nation’s trade deficit. Supporting US biodiesel injects some of that money back into local economies, as opposed to say, the economy of Saudi Arabia.

So which is really more expensive? I’ll let you decide for yourself.

MYTH #14: Biodiesel requires more energy to produce than is provided by the fuel.

FACT: The vast majority of literature on the subject shows a positive energy balance, meaning that more energy is available in the fuel than is used to grow the crop, press the seeds, process the oil into biodiesel, and distribute the product. The most common numbers I’ve seen say about 2-3 times more energy is produced, or 1 unit of energy in equals 2-3 units of energy out. [don’t leave it to me, see for yourself: [(1), (2)]. Compare this to corn-grain ethanol, which optimistically produces 25% more energy than is put into it (1 unit in equals 1.25 units out).

MYTH #15: Biodiesel increases net green-house gas (GHG) emissions when the entire production process is taken into account (farming, distribution, etc).

FACT: According to the University of Minnesota in 2006 (1), the production and use of soybean biodiesel decreases life-cycle greenhouse gas (GHG) emissions by 41% over regular diesel (NREL says 78%, page 4), and also decreases other pollutants like Carbon monoxide, PM10, and SOx. In fact, pure biodiesel reduces air toxics by 90% when compared to diesel fuel.

As an aside, according to the same Minnesota study, the life-cycle of corn-grain ethanol reduces GHG emissions by 12% and actually increases emissions of five major pollutants.

MYTH #16: Biodiesel causes deforestation.

FACT: You’ve almost certainly read accounts of biodiesel production destroying Brazilian, Malaysian, and Indonesia rain forests, or the problems with European biodiesel mandates. The most important thing here is that you define exactly which oil feedstock you’re talking about. What’s true for oil palms is not necessarily true for crops grown in the United States.

The US already produces a great deal of biodiesel from domestically-grown soybeans. There are some decent arguments to be made about how the international commodity price of soybeans is correlated to destruction of the Brazilian rainforest. But correlation isn’t the same as causation, and you’d first have to prove that the use of soybeans as a biodiesel feedstock is significantly raising prices on the international scene. It’s worth thinking deeply about, but it’s hard to tease out the details of such a complex issue (see Myth #23 for more).

Don’t forget that biodiesel can be made from many other feedstocks, like Canola, algae, and waste-vegetable oil (WVO). Like any other crops, soy and rapeseed can be grown sustainably or unsustainably. In some areas, WVO can be a major feedstock for making biodiesel (but this might not last for long!). In Oregon, for example, Sequential Biofuels makes about a million gallons of fuel each year from WVO.

To address the overarching issue here, the National Biodiesel Board has set up a Sustainability Task Force to quantify the impacts of biodiesel production and use, and to develop sustainable industry practices. Most people really aren’t interested in importing biodiesel from parts of the world where it’s questionably produced.

Want to know where your biodiesel is coming from? Ask your distributor or the manager of the filling station! Since biodiesel is somewhat novel and people are usually interested, they can probably tell you where it’s coming from.

MYTH #17: No way can we grow enough biodiesel to make a difference.

FACT: Some advocates, like Josh Tickell, claim there’s an additional 60 million acres of fallow US farmland available for growing soybeans. If a large portion, like 40 million acres, was put into use, it could produce 2 billion more gallons of vegetable oil (Tickell’s Biodiesel America, p. 151).

While this is theoretically possible, would inject lots of money into the US economy, and would further revitalize the agricultural sector in this country, I don’t know if it’s possible. Most people don’t like making fuel out of a food crop (even if almost all soybeans are fed to cattle anyway).

Ultimately, if there’s any hope of biodiesel making a huge difference, like more than 10% of petro-diesel usage, it’s going to have to come from the commercial production of algae.

MYTH #18: Biodiesel exhaust smells bad.

FACT: Well, this one is personal preference. I have had people tell me that they think the smell is disgusting (as if they would prefer diesel exhaust). I think B100 exhaust smells great. Sort of like French fries (or whatever food was cooked in it) but somehow…cleaner, and not as potentially nauseating. But biodiesel blended with diesel sort of smells like burnt, dirty oil (thanks to the diesel exhaust). In any case, it’s hard not to smile when you recognize the smell of a car or truck running on renewable fuel.

MYTH #19: Biodiesel exhaust produces more harmful emissions than diesel.

FACT: Biodiesel is the only alternative fuel that has completed all the testing requirements of the Clean Air Act. Biodiesel contains oxygen and it burns more completely than diesel fuel, resulting in reduced emissions. All major pollutants are reduced dramatically in biodiesel exhaust (most of them at least 50% for B100), except one—nitrogen oxides (NOx)—and that’s only for blends over B20 (see my post on the subject).

The most common report when users switch to biodiesel is the noticeable decrease in diesel smoke (the black, sooty clouds). B20 reduces air toxics (the most damaging pollutants for human health) by 20-40%, while B100 reduces them by as much as 90%. Sulfur oxides and sulfates (major contributors to acid rain) are almost completely eliminated. The only caveat is that nitrogen oxide (NOx) emissions can increase up to 10% with B100. If you would like to evaluate this for yourself, see the National Biodiesel Board’s emissions fact sheet.

New diesel technology like the Mercedes BlueTec and the 2009 Jetta TDI eliminate this problem by reducing NOx emissions by 80-90%.

All-in-all, biodiesel offers such a substantial reduction in emissions that it’s frequently used in sensitive areas like national parks and marine habitats. School districts all over the country have also turned to biodiesel as a way to reduce children’s’ exposure to toxic diesel exhaust.

MYTH #20: Diesel engines are more polluting than gasoline engines, so selling my car and buying a diesel is a bad idea.

FACT: It’s true that traditional diesel engines are 10-100x more polluting, in terms of soot/particulate matter, than their gasoline counterparts. But using biodiesel decreases both Carbon monoxide (CO) and CO2 emissions to levels below gasoline. Additionally, new model diesel engines are more efficient and have advanced catalytic converters that make them as clean as comparable gasoline models. When combined with biodiesel, new and old engines alike should offer significant emissions reductions.

For more information, see a timeline of all the new clean diesels that will be available in the US.

For a really sweet combination, check out the Mercedes 40 MPG diesel hybrid or VW’s 69.9 MPG diesel hybrid Golf.

While I’ve never actually seen a side-by-side comparison of B100 vs gasoline emissions in a comparable vehicles, I think it’s a safe bet that using biodiesel is better on some counts and worse on others.

No matter what, older diesels are currently in use and will continue to be used for the foreseeable future (due to long engine life). They’re also often the worst offenders in terms of air pollution. Switching these vehicles to biodiesel blends still provides tangible benefits.

MYTH #21: If I wanted to use biodiesel, there’s no way can I find a diesel to drive.

FACT: Yes, you can. I’ve written a guide to address this question. See Biodiesel Guide: 7 Steps to Buying a Diesel.

MYTH #22: Biodiesel is only used by crazy hippies and Willie Nelson.

FACT: Tell that to the US military, especially the US Navy (which is the largest single user of biodiesel), the National Parks Service, Postal Service, NASA, municipalities across the country, and more than 130 school districts and universities.

Addendum: MYTH (Or Fact?) #23: Biodiesel is Raising Food Prices

Ok, you got me. This list was only supposed to have 22 Myths, but I thought of one more that’s relatively important. Hit the link above for more…

That’s it!

Want to learn more? Biodiesel resources available at Gas 2.0:

If you choose to use biodiesel, this should be enough to get you started. Clearly, I can’t cover every issue in this post, but don’t stop here. Take a look at the following resources for more information:

Studies cited in the post:

(1) Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels

Jason Hill, Erik Nelson, David Tilman, Stephen Polasky, and Douglas Tiffany. PNAS published July 12, 2006, 10.1073/pnas.0604600103

(2) A Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus. Sheehan et al. May 1998. NREL/SR-580-24089.