Biodiesel Fuel: Homegrown Oil

Learn how clean, renewable biodiesel fuel is a sustainable alternative to petroleum-based fuel and how it can power any diesel engine.
By Greg Pahl
February/March 2006
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Biodiesel can be made from any oil-producing crop. For example, an acre of sunflowers yields about 102 gallons of biodiesel fuel.

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Imagine a renewable, clean-burning fuel that can be produced from local crops and could power a large number of existing vehicles — starting now. That fuel is biodiesel, which is made primarily of vegetable oil and alcohol and can be used in any modern diesel engine.

In the last few years, many farmers, environmentalists and other renewable energy advocates have begun promoting biodiesel as an alternative fuel that could replace at least a portion of the world’s petroleum-based diesel fuel market. Using biodiesel is an idea with widespread appeal because it pollutes far less than petroleum-based diesel and could help reduce our need for foreign oil.

In fact, biodiesel fuel already is widely used in Europe, where tax policies are structured to support its use. In Germany — where diesel engines power close to 40 percent of passenger cars — more than 1,800 filling stations offer biodiesel at a price competitive with that of petroleum-based diesel fuel.

In the United States, the public is just becoming aware of the potential of biodiesel, but the development of a biodiesel industry is already well underway. Many Midwestern soybean farmers have joined forces with other entrepreneurs to build biodiesel production capacity and infrastructure. At the same time, federal and state agencies and independent organizations have been testing biodiesel performance and setting production standards. With that firm foundation, the commercial biodiesel industry is growing rapidly, and biodiesel is becoming more accessible to drivers eager to fill their cars with this eco-friendly fuel. However, biodiesel can be used for more than fueling diesel-powered cars or trucks. In fact, the majority of the world’s heavy-transportation is diesel-powered, and all of these vehicles could be powered by biodiesel: buses, trucks, tractors, heavy machinery, boats and even trains. Biodiesel also can be used in any diesel-powered electrical generator, as well as in oil-fired furnaces and boilers (see Heat Your Home with Biodiesel).

Liquid Solar Energy

Although “diesel” is part of its name, pure biodiesel does not contain any petroleum-based diesel, also called “petrodiesel.” Instead, biodiesel is created from organic matter. It can be made from virtually any vegetable oil, including soy, corn, rapeseed (canola), peanut or sunflower — as well as from recycled cooking oil, animal fats or even algae.

Biodiesel has been called “liquid solar energy” because its energy content is derived from plants that capture solar energy during photosynthesis. The plants grown to produce biodiesel consume carbon dioxide (CO2), so they naturally balance most of the CO2 released when the fuel is combusted, offsetting a major contributing factor to global warming.

Using vegetable oil for fuel is not a new idea. When Rudolf Diesel invented the original diesel engine in the 1890s, he designed it to run on a wide range of fuels — including vegetable oils. But beginning in the early 1900s, diesel engines were adapted to burn mainly petrodiesel, a cheaper fuel. During the energy crisis of the 1970s, researchers began to reconsider vegetable oil fuels and found a simple method for turning vegetable oil into a usable diesel fuel. This process, called “transesterification” was developed in the late 1970s and early 1980s. It involves blending vegetable oil with alcohol, and adding a catalyst that will initiate the reaction that forms biodiesel.

Making Biodiesel Fuel

Because the process for making biodiesel is relatively simple and can be extremely low-tech, it has attracted a global community of “home brewers.” Although industrial-sized biodiesel facilities use high-tech equipment, the process is basically the same for a small-scale facility located in a garage or backyard shed.

Here’s how the process works. Carefully measured amounts of alcohol and vegetable oil are mixed with the catalyst. The alcohol can be either ethanol or methanol. (These two types of alcohol also are used in other types of fuel, see “Biodiesel and other Biofuels” later in this article.) For making biodiesel, methanol is usually preferred over ethanol because it’s less expensive and produces a more predictable reaction.

You can use one of two catalysts: sodium hydroxide or potassium hydroxide. Sodium hydroxide, which is commonly referred to as lye or caustic soda, is the same chemical used to unclog kitchen or bathroom drains. Potassium hydroxide can be used instead, but a larger quantity is required. These chemicals are dangerous and must be handled carefully.

Here’s a basic example of how you would brew biodiesel, using methanol as the alcohol and sodium hydroxide (lye) as the catalyst. Methanol and lye are mixed to create sodium methoxide, which is then mixed with the vegetable oil and stirred or agitated — and sometimes heated. The catalyst causes the oil to react with the alcohol and form two byproducts: methyl esters (biodiesel) and glycerin. The biodiesel rises to the top of the tank while the glycerin and the catalyst settle at the bottom.

After about eight hours, the glycerin and catalyst are drawn off the bottom, leaving biodiesel in the tank. In most cases the biodiesel needs to be “washed” with water to remove any remaining traces of alcohol, glycerin and the catalyst. In this procedure, water is mixed with the biodiesel, allowed to separate from the oil for several days and then removed.

Home brewers sometimes skip the wash process, but most commercial producers must use it to meet industry standards. If used cooking oil is the feedstock, the process is essentially the same, but may require more lye and filtration. To find more information on brewing your own biodiesel, see “Biodiesel Resources” at the end of this article.

Feeding Demand

One advantage of biodiesel is that a variety of crops from around the world will produce essentially the same biodiesel fuel. Hundreds of oil-producing crops can be used to create biodiesel, but some produce more vegetable oil than others (see “Crops for Making Biodiesel” later in this article). Soybeans are the primary biodiesel feedstock in the United States. Although they are a relatively low-yielding oil crop, one advantage of using soybeans is that they require less nitrogen fertilizer than many other oil crops.

Worldwide, rapeseed (canola) is the primary biodiesel feedstock (84 percent of production), followed by sunflowers (13 percent).

Currently, total global output of biodiesel is between 425 and 570 million gallons annually, with about two-thirds of that capacity generated in Western Europe. In 2004, the United States produced about 30 million gallons of biodiesel. That doesn’t go far toward meeting our need for oil: Every year, the United States consumes about 58 billion gallons of the petroleum fuels that biodiesel could potentially replace.

Just how much of that demand we could meet by expanding biodiesel production is the subject of much debate. One concern is that production of crops for biodiesel will always be limited by the amount of land needed to produce food. However, the United States has many resources that could be tapped immediately for biodiesel production.

We currently generate about 3 billion gallons of used frying oil every year. Assuming that half of this oil could be converted to biodiesel, that would represent about 2.5 percent of the current petrodiesel market. If half of the 11 billion pounds of animal fats produced in the United States could be processed into biodiesel, they would yield about 750 million gallons of biodiesel, or 1.25 percent of the petrodiesel market.

The 60 million acres of fallow U.S. cropland are another good resource for producing vegetable oil. If all this acreage were planted with rapeseed and yielded 100 gallons of oil per acre, that would produce another 6 billion gallons, or about 10 percent of the current petrodiesel market.

The total estimated production from all of these sources comes to 8.25 billion gallons, or about 14 percent of the U.S. petrodiesel market. In Europe, biodiesel has the potential to replace somewhere between 10 percent and 15 percent of the current petrodiesel market.

However, this projection does not take into account potential biodiesel production from algae, a promising new oil crop. Pond algae may seem like a bizarre source of diesel fuel, but most of the world’s petroleum resources were formed from vast amounts of algae that were transformed by heat and pressure over millions of years.

Today, algae can be grown in ponds in just a few days, and oil can be extracted directly from the harvested algae. Some experts predict that one acre of algae could yield an enormous amount of oil — 3,654 gallons per year or more. Research on algae is still in the beginning stages, and any large-scale use of algae for biodiesel would require massive investments in production facilities. That would take many years and large amounts of money to develop, but it might be possible if the United States were willing to commit the resources to developing this renewable fuel.

Buying Into Biodiesel

In May 2001, the first commercial biodiesel pump opened in Sparks, Nev., followed less than 24 hours later by another in San Francisco. Since then, biodiesel fuel stations and wholesale retailers have been increasing in numbers nationwide; there are now more than 600 retail fuel outlets in the United States. To find a retailer near you, visit the National Biodiesel Board.

The price of pure biodiesel has been significantly higher than diesel fuel. However, biodiesel can be mixed with petrodiesel in any percentage, which makes it possible to produce blends that are less expensive than 100 percent biodiesel. Biodiesel often is sold as B20 (20 percent biodiesel and 80 percent petrodiesel), a concentration that has demonstrated significant environmental benefits over petrodiesel, with only a small increase in cost to consumers.

For example, according to the most recent report from the U.S. Department of Energy, the average nationwide price of pure biodiesel was $3.40 per gallon in September 2005. In comparison, petrodiesel averaged $2.81 per gallon, and B20 cost just 10 cents more at $2.91 per gallon.

Biodiesel is catching on in many niche markets, largely because it is a cleaner-burning fuel. Biodiesel is free of lead, contains virtually no sulfur and produces lower quantities of cancer-causing particulate emissions than petrodiesel. (See “Pros and Cons of Biodiesel” later in this article for more about biodiesel emissions.) In particular, using biodiesel in school buses makes a lot of sense. Young children are more susceptible than adults to the toxic and potentially cancer-causing emissions from petrodiesel. This fact has led more than 50 school boards across the nation to require that their buses use biodiesel fuel.

This cleaner-burning fuel also is an attractive option in recreation areas. Yellowstone National Park was the first national park to test biodiesel as a fuel, and the project was such a success that the National Park Service has introduced biodiesel to another 20 parks across the country. Biodiesel also is being used as vehicle fuel by numerous cities including Columbia, Mo.; Breckenridge, Colo.; and Missoula, Mont.; as well as by many universities, including Harvard and Purdue.

Europe has been the main focus of biodiesel activity for many years, but countries around the world are developing active biodiesel programs, including India, Brazil and Canada. It will take an enormous cooperative effort from the entire global community to wean ourselves from our present addiction to petroleum. Biodiesel is not the single solution to all our energy problems, but it can be part of the transition from our current near-total dependency on fossil fuels to the use of a wide range of renewable energy resources. At the same time, it would create jobs, assist farmers, reduce pollution and promote greater energy security.

Biodiesel and Other Biofuels

Biodiesel can be used in any engine or heater that runs on diesel fuel or heating oil. This clean-burning fuel is manufactured from vegetable oil (or animal fats) and alcohol.

Biodiesel blends combine biodiesel and petroleum-based diesel to create a fuel with less sulfur and lead than straight petrodiesel. One common blend is B20 — 20 percent biodiesel and 80 percent petrodiesel. B100 is 100 percent biodiesel.

Straight Vegetable Oil (SVO) can power modified diesel engines. (Recycled cooking oil often is used instead of new oil.) The concept behind biodiesel is modifying vegetable oil so that it can be used in diesel engines; those who use SVO modify their vehicles instead of the oil.

Ethanol, often called “grain alcohol,” can be blended with gasoline. Ethanol is often produced from corn, and it is used in vehicles designed to run on ethanol or in gas engines at low concentrations — usually 10 percent ethanol, 90 percent gasoline.

Methanol is an alcohol fuel that is similar to ethanol, but it is used only in specialized vehicles. It can be made from wood, but is usually derived from natural gas.

Pros and Cons of Biodiesel Fuel


  • Can replace petroleum-based diesel in any modern diesel engine.
  • Is an excellent lubricant that can increase engine life.
  • Is free of lead, contains almost no sulfur or aromatics (toxic compounds such as benzene, toluene and xylene), and substantially reduces emissions of unburned hydrocarbons, carbon monoxide and particulate matter (soot), which have been linked to respiratory disease, cancer and other adverse health conditions. The production and use of biodiesel results in a 78 percent reduction in carbon dioxide emissions, according to a 1998 study from the U.S. Department of Energy and Department of Agriculture.
  • Has a positive fossil-energy ratio, meaning the energy stored in biodiesel is greater than the fossil fuel energy required to replace it. Although one recent study found a negative fossil-energy ratio for soy- and sunflower oil-based biodiesel, at least 10 other studies have found positive ratios for biodiesel, including the 1998 study mentioned above.
  • Is safer to store and transport than petrodiesel fuel and actually can be shipped via courier (FedEx or UPS, for example) in small quantities because it is not considered a hazardous material.
  • Can be used as a substitute or additive for home heating fuel, normally without any major modifications to a standard oil-fired furnace or boiler.
  • Production of crops for biodiesel supports local economies.


  • Sometimes more expensive than petrodiesel, but the difference in cost is disappearing because of recent federal tax legislation and the rising cost of petroleum.
  • Emissions of nitrogen oxides (a contributing factor in the formation of smog and ozone) are sometimes slightly greater with biodiesel when used as a vehicle fuel, but these emissions are lower when it is used as a heating fuel due to the different combustion process.
  • “Clouds” at extremely cold temperatures, causing some cold weather challenges. Biodiesel is more susceptible to this problem than petrodiesel.
  • Used in high concentrations, biodiesel will eventually soften rubber hoses and gaskets in older diesel engines (those made prior to 1994), resulting in leaks. Using biodiesel in these vehicles requires replacing these rubber parts.
  • Will dissolve the petrodiesel deposits that coat the sides of old fuel tanks and fuel lines, possibly clogging the fuel filter (usually a one-time problem).
  • In warm weather, biodiesel is more susceptible than petrodiesel to the growth of bacteria and mold. Keeping water out of the fuel will help to eliminate this problem.

Crops for Making Biodiesel Fuel

Oil-producing crops are found all over the world. Below are oil yields from crops that can be used to produce biodiesel.

Oil Crop: Yield per Acre

Oil Palm: 635 gallons

Coconut: 287 gallons

Jatropha: 202 gallons

Rapeseed (canola): 127 gallons

Peanut: 113 gallons

Sunflower: 102 gallons

Safflower: 83 gallons

Mustard: 61 gallons

Soybean: 48 gallons

Corn: 18 gallons

Biodiesel Resources

National Biodiesel Board

(800) 929-3437

The national trade association representing the biodiesel industry. Its “Guide to Buying Biodiesel” includes a list of fuel retailers.

Biodiesel and SVO Discussion Forums

Get technical information for brewing biodiesel.

Biodiesel America

Home of a campaign to expand the use of biodiesel in school buses.

Veggie Avenger

Comprehensive information about biofuels, including straight vegetable oil.

Alternative Fuels Data Center

The U.S. Department of Energy’s site for information on biodiesel and other alternative fuels.


Biodiesel Discussion Forum

The Web’s largest biodiesel discussion forum and message board on brewing biodiesel at home.

Discussion covers all aspects of biodiesel, with smaller regional forums by country and state.


Biodiesel: Growing a New Energy Economy

By Greg Pahl

From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel

By Joshua Tickell

Adapted from Biodiesel: Growing a New Energy Economy by Greg Pahl (Chelsea Green Publishing, 2005).

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