Mother Earth News - Mother Earth News 2006

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 worlds 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 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 worlds 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).

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.

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.

Heres 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.) For making biodiesel, methanol is usually preferred over ethanol because its 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.

Heres 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.