What is Biodiesel ?

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Biodiesel Fact Sheet


The use of vegetable oils in diesel engines is nearly as old as the diesel engine itself. The inventor of the diesel engine, Rudolf Diesel, used groundnut (peanut) oil as a fuel for demonstration purposes in 1900. Some other work was carried out on the use of vegetable oils in diesel engines in the 1930's and 1940's. The fuel and energy crises of the late 1970's and early 1980's as well as accompanying concerns about the depletion of the world's non-renewable resources provided the incentives to seek alternatives to conventional, petroleum-based fuels.

They now occupy a prominent position in the development of alternative fuels. Hundreds of scientific articles and various other reports from around the world dealing with vegetable oil-based alternative diesel fuels ("biodiesel") have appeared in print.


Biodiesel is a diesel cycle fuel manufactured from vegetable oils, recycled grease, or animal fats. The general chemical designation for biodiesel is ‘Fatty Acid Methyl Esters.’ It has advanced from being purely experimental fuels to initial stages of commercialization. It is technically competitive with or offer technical advantages compared to conventional diesel fuel. Besides being a renewable and domestic resource, biodiesel reduces most emissions while engine performance and fuel economy are nearly identical compared to conventional fuels.


In short, biodiesel is a much cleaner burning fuel than standard diesel fuel. Because it is not a fossil fuel, and therefore its combustion does not result in added atmospheric carbon dioxide originating from beneath earth’s surface. Table 1, below, compares emissions from B100 combustion and B20 combustion with the combustion of standard diesel fuel.

Table 1 – Biodiesel Emissions vs. Diesel Emissions

Engine Life

Diesel engines are designed to run on fuel that meets the diesel standard ASTM D-975. Biodiesel has its own standard to ensure quality, ASTM D-6751. To a large extent, the longevity of diesel engines is a result of the lubricity of diesel fuel. Prior to the early 1990’s diesel fuel had adequate lubricity to ensure minimal wear on crucial, close-tolerance engine parts. Since about 1993, however, in order to clean up the sulfur and aromatic hydrocarbons in diesel emissions, many of the compounds responsible for diesel’s lubricating properties have been removed. In March, 2000, Quality Management Systems Manager for Stanadyne Automotive Corporation, (Stanadyne makes diesel injection components for Ford, Chevy, and other domestic companies) Paul Henderson stated the following to the Chairman of the Kansas House Environment Committee:

“There have been numerous examples from the field where lack of lubricity in the fuel has caused premature equipment breakdowns and in some cases, catastrophic failures. This problem will be more dramatic as EPA moves to further reduce the sulfur levels in petrodiesel fuel.” – NBB

On-Road Vehicle Applications

If your vehicle is 1993 or newer, no conversion is necessary, but you will need to change your fuel filters as Biodiesel cleans the fuel tank. If your vehicle is older than 1993, you will need to change your fuel filters, as well as monitor your fuel lines for degradation. In October 1993, diesel fuel formulation changed to reduce sulfur, and older natural rubber parts were replaced with newer materials. This is why newer cars and trucks have hoses that are usually compatible with Biodiesel. (Note: New vehicles will not have sediment buildup and will only require regularly scheduled filter changes.)

Off-Road Vehicle Applications

Older off-road vehicles such as tractors, construction equipment, etc, and generators may not be equipped with Biodiesel compatible hoses. Please monitor your equipment for degradation, as well as making the necessary fuel filter changes.

Fuel Filter Changes

If you are switching to a blend of Biodiesel, B20 and up, then you will need to be aware of several things. The solvency of Biodiesel will clean old petroleum residues and deposits from your tank and clean the fuel system. These residues will be caught by your fuel filters. Switching to Biodiesel Blends B20 or above will therefore necessitate 2-3 filter changes. Please note that each vehicle is different, and that the fuel filter changing schedule may vary based upon age of vehicle, frequency of use, if the tank is normally kept near full, as well as other factors. B100 will have a more rapid solvency effect than B20.

Possible Fuel Filter Change Schedule for B100

Fuel Lines, Gaskets, Seals and Metals

On pre-1993 vehicles and equipment, there are often fuel system components that will degrade over time when exposed to high levels of Biodiesel. Degradation in fuel lines will be evident by an increase in the pliability of the line, then the line will “sweat” and look wet, and eventually it will start to leak. Please replace the line before this happens. Even though Biodiesel is non-toxic and biodegrades quickly, it is still best to keep it off the ground.

Fuel lines can be easily monitored yourself, or you can tell your mechanic what to look for and they can help. The gasket material of tank lids may be subject to degradation as well. It is possible that a fuel pump could malfunction because its seals degraded. This would be the worst case scenario. Copper, brass, bronze, tin, lead, and zinc will react with Biodiesel if in contact for long periods of time, forming sediments. Although diesel systems should not have these metals, check for them if you continue to have filter plugging beyond the transitional time.

What else will Biodiesel affect?

The Biodiesel can damage your paint if it is continually spilled around the fuel intake. It is therefore best to wipe off any Biodiesel that spills onto your vehicle with a spray cleaner such as Simple Green and a rag or paper towel. Similar to Petroleum Diesel, if Biodiesel is continually spilled on the same piece of concrete, it may dissolve the adhesives out of the concrete. All Biodiesel soaked rags should be treated as a combustible and stored in a safety can. As with any fuel, be responsible with handling procedures.

Biodiesel in Cold Temperatures

As with standard diesel fuel #2, biodiesel must be winterized in cold weather. It generally has a slightly higher cloud point than diesel fuel #2. The cloud point of the fuel may depend somewhat on the actual type of oil used to make the biodiesel. Generally speaking, B100 can be used year round in a climate like California’s central valley, whereas it may need to be blended with diesel fuel #2 and/or diesel fuel #1 (kerosene) in the wintertime in colder climates. If you plan on operating in a cold environment with sustained temperatures below freezing for days, please consider the following tips.

Tips for cold weather:
  • Keep your tank close to full; a large amount of fuel will gel more slowly than a small amount.
  • Make sure your glow plugs are in good condition (especially older vehicles).
  • Blend Biodiesel with at least 20% diesel #2 or diesel #1 when using in cold climates.
  • Use a cold weather additive with Biodiesel in the winter.
  • If your fuel lines do plug, try pouring hot water on them. Do not continue to crank your engine over if your fuel system is plugged, this can damage the fuel pump.

Will Biodiesel void my warranty?

Using Biodiesel does not void your warranty. A manufacturer’s warranty covers parts and workmanship. If there is a problem from parts and workmanship, it is the responsibility of the manufacturer to fix it. Engine manufacturers do not honor warranties for petroleum diesel, nor will they honor warranties for Biodiesel.

Safety and Health Effects

The safety of Biodiesel emissions compared to petroleum diesel emissions is well established. EPA Health Effects Tier 1 and Tier 2 Tests have been completed and show that Biodiesel is an extremely safe fuel.
  • Biodiesel is non-toxic (less toxic than table salt).
  • Non-flammable (325 degree flashpoint vs. diesel’s 125 degree), and
  • Biodegradable (in water, as quickly as sugar), making it particularly attractive for marine and sensitive environment applications.

The EPA’s emissions data show substantial emissions reductions, with an average total reduction of 70%. Biodiesel will not harm skin and will only cause mild irritation if splashed in the eyes. It is recommended that you rise thoroughly with clean water if this occurs. Biodiesel is truly safer to use, handle and store.

Other Cautions

Biodiesel is a mild solvent. On prolonged contact with painted surfaces, it may deface some paints. The most commonly encountered problem with solvency is biodiesel’s tendency to “clean out” storage tanks, including vehicle fuel tanks and systems. Diesel fuel #2 tends to form sediments that stick to and accumulate in storage systems. The older the system, and the poorer the maintenance, the thicker the accumulated sediments become.

Biodiesel (blends greater than B20) will dissolve these sediments and carry the dissolved solids into the fuel systems of vehicles. Fuel filters catch most of it, but in severe cases, the dissolved sediments may cause injector failure.

Biodiesel’s solvency can affect some nitrile (rubber) fuel system components. Nitrile components are typically found in pre-1993 vehicles. These can eventually swell, soften, and fail over the course of several months when used with B100. If B100 will be used for prolonged periods of time, then it is a good idea to at least keep an eye on rubber fuel lines, if not simply replace them. Blends of less than B20 will not have an adverse affect on nitrile components.

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