Introduction to biodiesel

Diesel drivers are an interesting niche group.  Some are gearheads interested in the mechanical aspects of diesels or have exposure to diesels through work or friends and family.  Others just want a car with greater fuel economy with similar performance to a gasoline car.  Environmentalists want to reduce their use of fossil fuels and are interested in using waste veggie oil (WVO) or biodiesel as a gasoline alternative.  I fell into all of these groups so I tried to learn as much as I could which I have condensed here into 1 easy to read page.  If you have a question about biodiesel, get an answer at the myturbodiesel discussion forums

Table of Contents

  1. Introduction to biodiesel
  2. Biodiesel vs. waste vegetable oil
  3. Introduction to making biodiesel at home
  4. Further reading/useful links

Related links: 1000q: making biodiesel yourself

Introduction to biodiesel

To dispel one of the biggest myths about biodiesel, it's not used cooking grease or straight veggie oil.  That's like saying gasoline is the same as crude oil.  Biodiesel is a  fuel that can be used diesel engines or boilers and is refined from oils or grease and is actually one of the most common alternative fuels.

Unfortunately, biodiesel is not a magic bullet that will solve all of the world's energy problems.  It's unlikely to become a mainstream fuel in its current form but it's very valuable as a fuel additive to petrol diesel.  It can be added in a percentage up to 100% which is really helpful in North America because the refineries here are set up to produce much more gasoline than diesel out of every barrel of crude oil.  It also decentralizes the production and distribution of fuel to the local level and where the fuel is used.  As diesel cars become more common in the US and people recognize the need for higher fuel economy cars, biodiesel and other diesel fuels will also become more popular.  Higher fuel economy legislation and high fuel prices are among the reasons why car makers are bringing back diesel cars to the US market in larger numbers.  VW, GM, Chevy, Ford, BMW, Audi, and Mercedes Benz all have diesel cars and trucks for sale in the US right now.

Biodiesel is cleaner burning than petrol diesel, a 100% renewable fuel, and can be domestically grown and processed.  It can be used in modern diesel engines and oil-fired home heating systems with little or no modifications. It's also biodegradable, less toxic than table salt by mass, and with greatly reduced odor and emissions compared to diesel fuel.  It also has a higher cetane than most US diesel available so diesel engines will run better on it.  From an environmental perspective, it's greener than petrol diesel.  From an economic perspective, it can be cheaper than petrol diesel.  From an engineering perspective, it's better for the engine.  From a geopolitical and national security perspective, it can be domestically grown and produced.  It can also be locally produced and distributed near or even right at the point of use which saves transportation costs and takes the control of energy out of the hands of a few companies.

Unlike veggie oil, its viscosity is much closer to that of diesel fuel, reducing the chance of stressing the mechanical fuel pumps, and requires no modification to a modern diesel car.  Unlike a grease car, or greaser, it does not require modification to the car or require the car to be started and stopped on diesel fuel to flush the fuel lines.  If the fuel lines are not flushed prior to shut down, a grease car may not be able to start with veggie in the fuel lines.  Biodiesel gels at a higher temperature than diesel.  Diesel fuel begins to gel at -20oF, 100% biodiesel without winterization begins to gel anywhere from 14oF to 50oF depending on its source.  Biodiesel available at retail fuel pumps, usually 20% biodiesel/80% diesel does not suffer from these problems because it has winterization additives added.  

The other problem involves using biodiesel in the newest VW and Audi TDI diesel engines equipped with diesel particulate filters (DPF).  DPF problems or DPF clogging could result if the trapped particulates aren't burned off.  DPF filters are found on V10 VW Touareg 2006 and newer and all 2009 and newer VW or Audi TDI.  Biodiesel use in these cars isn't long term enough to draw any real world conclusions but the most reliable way to prevent DPF failure is to use a DPF delete kit with aftermarket car computer programming.  

DPF filter clogging on your VW or Audi TDI could result due to biodiesel's higher boiling and flash point.  The current method of DPF filter regeneration on VW and Audi is with post combustion fuel injection to raise the exhaust gas temperature EGT.  This puts some fuel in the crankcase and because of the properties of biodiesel, it accumulates and dilutes the engine oil.  To understand the specific reasons why and how the emissions system works on the newest clean diesels, see 1000q: DPF and Adblue FAQ for details.  Obviously, bypassing the DPF filter is tampering with federally mandated emissions equipment and is illegal.

Here is a .pdf article from the US Department of Energy summarizing more basics of biodiesel.

Biodiesel and warranty coverage in a VW TDI or Audi TDI engine

All VW Audi TDI engines will run fine on biodiesel in all years of TDI.  VW and Audi's recommendation is to use a maximum of B5 but the 1996-2006 TDI all run fine on B100.  Almost none of these cars are under warranty anymore so it's a moot point.  The 2009+ Golf, Jetta TDI , and 2010+ Audi A3 will also run fine on B100 but VW's official limit is only a maximum of B5.  Again, the engine itself will run fine but the clean diesel exhaust emissions system is not be compatible with B100 and it will result in engine oil dilution, which could cause engine damage. In Feb 2013, VW responded to Illinois' biofuel mandate by sending the letter (thumbnail to the right) allowing up to B20 for TDI registered in Illinois.

They cannot void your car's warranty because of biodiesel use!  For example, the radio's warranty is not effected because of what fuel you use.  However, if they refuse a warranty claim on the engine or exhaust system, it's up to you to take responsibility to prove your case.  Laws vary but generally speaking, you would have to prove that the manufacturer is responsible for the problem and/or that the fuel is not responsible for the problem.  The Magnuson-Moss Warranty Act covers consumer product warranties but the manufacturer could make the case that bad fuel caused the problem.

Biodiesel used in fuel on VW TDI and Audi TDI must meet the American Society of Testing and Materials standards ASTM D975.  

The standard specifications are shown below:

Property  ASTM Method  Limits  Units
Flash Point D93 52 min. °C
Water and Sediment D2709 0.050 max % vol.
KinematicViscosity,40C D445 1.9 - 4.1 mm2/sec.
Ash D482 0.01 max. % mass
Sulfur (Grade No.2) D129 0.50 max. % mass
(Grade No. 2-Low Sulfur)
D2622 0.05 max. % mass
Copper Strip Corrosion D130 No. 3 max. -
Cetane D613 40 min. °C
Pour Point D97 ------- °C
Cloud Point or LTFT/CFPP D2500 or D4539/D6371 Depends on
% mass
Density, 15°C D1298 ----- mg KOH/gm
Ramsbottom Carbon D524 0.35 max. kg/m3
Residue D976 40 min. mg KOH/gm
Cetane Index
D1319 35 max. % vol.
Distillation Temperature,
90% Recovered
D86 282-338 °C
Lubricity, HFRR @60°C D6079 520 max microns

More details about biodiesel 

One of the advantages of biodiesel over petrol diesel is that it is a green fuel less toxic by mass than table salt.  Through a chemical process called transesterification, it is refined from veggie oils and grease. Vegetable oils primarily consist of triglycerides: three carbon chains connected by a glycerin molecule. In the reaction process, an alcohol (methanol or ethanol) is used with a catalyst (potassium or sodium hydroxide) to separate the glycerin molecule from the carbon chains. The long carbon chains in biodiesel have a very similar profile to petroleum middle distillates. The fatty acid alkyl esters, the chemical name for biodiesel, is then separated from the co-product glycerol. The glycerol mixture can be refined into glycerin - a valuable pharmaceutical ingredient used in soaps and other health and beauty products.

Biodiesel fuel also burns up to 75% cleaner than conventional diesel fuel made from fossil fuels. Biodiesel substantially reduces unburned hydrocarbons, carbon monoxide and particulate matter in exhaust fumes. Since biodiesel contains no sulphur, it eliminates sulphur dioxide emissions. And biodiesel is plant-based and adds little or no CO2 to the atmosphere. Plants take up carbon dioxide from the atmosphere; burning plant (or animal) products in an engine releases the CO2 uptake back into the atmosphere, to be taken up again by other plants. The CO2 is recycled, atmospheric CO2 levels remain constant. Thus biodiesel does not increase global warming like fossil fuels, which release large amounts of new (or rather very old) CO2 which has been locked away from the atmosphere for aeons. The ozone-forming potential of biodiesel emissions is nearly 50% less than conventional diesel fuel. For a fact sheet from the National Biodiesel Board's complete evaluation of biodiesel emissions, refer to this pdf file:

There is a controversy about how green biodiesel is because of the carbon accounting.  In some areas, forest may be cleared to make biodiesel producing crops and there is an inherent cost to producing, manufacturing, transporting, and consuming fuel.  To dispel a major myth about the current controversy, biodiesel and other green fuels are not the leading factor in higher food costs.  Food costs experienced a spike due to world economic factors, a commodities bubble, politically motivated subsidies and trade tariffs, with diversion of acreage to green fuels being a minor contributor.  The primary reason for the increase in food cost is the increase in crude oil prices and increased worldwide food and fuel demand.  It's more expensive to farm, process, and move food across the country due to higher fuel prices, which raises the price at the supermarket.  A minor explanation is that some of these diverted resources were not intended for direct human consumption ie., animal feed or processing corn into high fructose corn syrup.  I'm sure that there are many small factors that I am leaving out and a full explanation is beyond the scope of this article. 

While ethanol feedstock was never destined for human consumption, it does take away somewhat from acreage destined for human consumption and animal feedstock.  The counterargument to this is that the same acreage or cleared forest may have been used for some other industrial use so it's wrong to say that the latest carbon accounting is the correct one.  Because biofuels and their impact are so new, at this point it's best to do what you want because no single argument is conclusively the correct one.  In addition, biofuel use should be adaptable.  Ethanol production with sugarcane in Brazil is much more green than ethanol producion in the US with corn.  Geothermal energy is a no-brainer in Iceland but it wouldn't work in Texas, where wind farms are becoming a major source of energy.  Hydroelectric is great at a waterfall but a bad idea in the Death Valley Desert.  In any case, I am sure that biodiesel has a place in the future.

Biodiesel's ease of use is the same as a gasoline pump if purchased at a retail or fleet pump.  It requires no modification to any modern diesel car at all. You can pump it into the fuel tank and mix it with petrol diesel in any proportion. Older cars, typically before 1995, that used rubber fuel lines require any rubber fuel lines to be replaced with a biodiesel safe line.  One of the more common mixtures sold at commercial pumps is B20, a mixture of 20% biodiesel, 80% diesel. Some pumps even offer 100% biodiesel, called B100.  It is a sulfur free fuel. It can also be cheaper than both gasoline and diesel. Many people make their own biodiesel at home with costs of anywhere from 25cents/gallon to 75cents/gallon. More on making homebrew biodiesel here.  Buying biodiesel or a biodiesel blend at the pump generally costs a few cents more than regular diesel.

Ultimately, buying biodiesel at the pump costs more, but is far more convenient than homebrewing.  Commercially available biodiesel also must meet standards including: complete reaction of chemicals, removal of catalyst, glycerin, alcohol, and free fatty acids.  There are currently no state or federal rules that I am aware of that regulate its taxation if made in small quantities for your own consumption.  There are a few laws coming up that do allow for small scale home production and consumption but you must stay under a certain amount produced/year.  If you make your own biodiesel from used grease, its cost can be anywhere from 25cents/gallon to $1/gallon.  Please note that biodiesel and/or biodiesel related material and activities may be regulated by fire codes and may be considered a fire hazard, always comply with any local, state, or federal regulations regarding your biodiesel making materials, storage, equipment, methods, production, or biodiesel use.

The infrastructure of distributing biodiesel already exists, so the cost of supplementing petrol diesel with biodiesel is almost nothing compared to hydrogen, hydrogen fuel cell, or other alternative fuel sources.  The overall price of supplementing diesel with biodiesel is even less than that of adding ethanol to gasoline, since all diesel cars can run biodiesel, but few US gasoline cars can run ethanol.  For older gasoline cars, running even small amounts of ethanol may cause corrosion in engines and fuel system components such as fuel injectors.  

Biodiesel is also not only better for the environment, it is also better for a diesel engine. It provides better lubricity than diesel fuel which helps lubricate the engine's various parts, and also has a cleansing effect.  Lubricity can increase by as much as 65% with just a 1% biodiesel blend, so it is very valuable even as a fuel additive, especially with today's ultra low sulfur diesel.  In fact, there have been many independent tests which have shown that it's possible to get a batch of bad fuel which does not meet petrol diesel standards.  Adding 1-5% biodiesel will almost certainly prevent any damage to the fuel pumps and injectors from low fuel lubricity.  .

When people first use a high percentage biodiesel blend or full biodiesel on high mileage cars, they often think the biodiesel is causing a problem because they see smoke or have stumbling/stalling related to a clogged fuel filter.  Biodiesel actually cleans out the gunk and residue deposited from years of diesel use, causing it to get burned and create smoke.  If the build up is too severe, the sudden release of gunk can actually clog the fuel filter, stalling the engine.  Low mileage cars should not have significant build up, and should not be as susceptible to these problems.  Its viscosity depends on the source of grease and the quality of the maker.

Older cars that have used biodiesel for a long time may develop fuel leaks if you go back to petrol diesel.  Due to age/use and the switch to ultra low sulfur diesel, USLD, stopping biodiesel use can result in fuel leaks from the injection pump.  The pump may just leak due to age/use as well.  Replacing the seals on the pump will stop any fuel leak.  

Lastly, it provides a geopolitically more stable fuel and increases national security.  Since it is usually produced entirely from domestically grown plants or waste grease, the supply of fuel is not interrupted by foreign conflict or hostile governments.  However, critics of hybrid, biodiesel, hydrogen, ethanol, and electric cars, state that any one fuel source or technology cannot replace the nation's addiction to oil and they are right.  But I would say that those critics are missing the point: much like gambling or playing the stock market, you do not invest all your resources in one spot.  Would you say that since all cancer will not be cured with X cancer treatment, that you should not pursue any further research of cancer treatment?  No!  By diversifying fuel sources into biodiesel, hydrogen, ethanol, and electric, a secure and economically efficient future will include cars with a variety of fuels and technologies.  As the current electric-gas hybrid craze proves, if automakers make green cars that make sense, people will buy them.  In the future, until the market sorts this emerging technology out, expect to see a return to the technologies of the early days of the automobile - pure electric cars, diesel cars, gasoline cars, hybrids, and maybe even steam cars!

For more information on biodiesel and how to homebrew it, follow this link to 1000 answered questions: introduction to making biodiesel at home


Biodiesel vs. waste vegetable oil

First, this article does have a bias toward biodiesel because it is my personal opinion that using biodiesel is a superior fuel to WVO and that using biodiesel is better for most people.  I have included links at the bottom for those who want to see examples of WVO conversions or want to learn more.  Here is a quick list of pros and cons comparing biodiesel and WVO.  Please note that the pros and cons are specific to the VW TDI only!  The cons of WVO used in a light duty VW TDI are not the same as WVO used in an inline pump Mercedes Benz or older Dodge Cummins Ram.  It is possible to use WVO in a VW TDI successfully for many years, but the odds and the experiences of others strongly suggest that biodiesel is a better option.

The main reason is because you can buy retail biodiesel as a pump and go fuel.  Making biodiesel yourself or processing grease at home require responsibility, consistency, and 100% adherence to procedures and safety.  I am an optimist but the fact is that most people will make a mistake sooner or later.  Mistakes result in a tow to the mechanic, failure of parts, damage to parts over the long term, or accelerated engine wear.  If you can live with any possible economic penalties from your mistakes AND are the type of person who finishes projects, does their research, double checks things, maintains their car religiously, and has a high level of discipline then you could probably make biodiesel or run the car on WVO and have no problems.  If you are not, be prepared for the cost of the mistakes.

Biodiesel Pros:

-Can be made at home within the boundaries of local, state, and federal laws

-If made at home, is tax free with a much lower final cost than buying pump retail petrol diesel

-No modification to any modern diesel car necessary

-Provides improved lubricity to the engine, even with just 1% biodiesel blended with 99% diesel

-Provides cleansing effect on engine and fuel system

-Can be mixed in any proportion with petrol diesel

-Available at some retail or fleet fuel pumps

-Much improved emissions over diesel, 0% sulfur fuel, better odor than diesel fuel

Biodiesel Cons:

-Biodiesel home brewing ingredients use hazardous chemicals that are potentially hazardous or fatal

-Homebrew biodiesel produces waste products and hazardous gases

-Biodiesel making equipment may be a fire hazard, subject to local, state, and federal regulation

-Gels at a higher point (anywhere from 20-60oF, dependant on oil and additives) than petrol diesel

-If you homebrew and use waste grease, you have to collect it.  This is messy and harder than going to a pump and sliding your credit card.

-The official limit on biodiesel in VW TDI is 5% although many have used 100% with no problems

-The 2009 and 2010 TDI may have issues with biodiesel over the long term due to the post combustion injection and regenerating exhaust filter

WVO Pros:

-Tax free, less expensive/gallon than biodiesel due to less processing

-Better emissions than petrol diesel

WVO Cons (some specific to the VW TDI)

-Worse emissions than biodiesel due to incomplete burn

-Will always mix with the engine oil to some degree and contaminate the engine oil which MAY cause severe engine damage

-Cannot be mixed with diesel in main fuel tank for regular use

-Requires medium modification to car's fuel system and minor modification to the car's interior

-Warm up period required before engine can switch from diesel to WVO

-If fuel lines are not purged of WVO before engine shut down and the car cools down enough, the fuel lines will clog.  If the fuel lines are clogged, car may not start, requiring fuel lines to be heated, then flushed

-VW fuel injection pump may not be designed for WVO's higher viscosity and higher temperatures of heated WVO.  The heat and greater viscosity could cause greater wear over the long term

-Current kits on the market for WVO conversions leave much to be desired

-You have to collect waste grease-this is the messiest part of using WVO or biodiesel

-It can cause valve buildup if not properly combusted, as seen below.  The pictures are from tdiclub and there is some controversy about the exact cause but it's certainly related to WVO use.

As you can see, the only major advantage that WVO has over biodiesel is that you don't have to process it with chemicals.  It still has to be collected, filtered, and settled.  In my opinion, a much better option is to process the WVO into biodiesel because it is better for the engine, turbo, and fuel pump due to viscosity and temperature, better for emissions, better for the engine oil, and requires no modification to the car.  Again, it is possible to successfully use WVO and not have a problem but there is less chance of having problems with biodiesel.  WVO supporters say that a diesel engine demonstration showed a diesel running on peanut oil during the early days of automobiles.  Back then, engines were less powerful, much simpler, and didn't last very long.  Today, high pressure direct fuel injection, higher combustion pressures, and expectations of cars running 200,000+ miles, in my opinion, make WVO a poor choice for VW TDI.

Further information on WVO:

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