Biodiesel Basics

Biodiesel is a growing part of our fuel supply, but its potential as an oil saving solution depends on what it’s made from.
How biodiesel works
Photo: United Soybean Board

What is biodiesel?

Biodiesel is a renewable fuel derived from vegetable oil or animal fats that can be added to conventional diesel to create a blend or used on its own.

All of today’s diesel vehicles can use up to 5 percent biodiesel (“B5”), which is blended into conventional diesel under the specifications governing diesel fuel (ASTM specifications).

Many vehicles, especially trucks, are certified to use 20 percent biodiesel and 80 percent conventional diesel (“B20”). In the United States, the majority of biodiesel is made from soybean and other edible vegetable oils, although biodiesel made from used cooking oils, animal fats, and wastes is increasing rapidly.

Biodiesel is different than “renewable diesel,” a related product also made from fats and oils. Renewable diesel is processed with hydrogen to remove oxygen, resulting in a diesel or jet fuel substitute, and is commonly called a “drop-in fuel.”

Drop-in renewable diesel is essentially indistinguishable from conventional diesel or jet fuel and can be blended at almost any level, making it an attractive option for military or airline use.

Global warming and biodiesel: it depends

The global warming pollution created by biodiesel depends on how it is made and (especially) what it is made from.

Biodiesel made from waste materials or used cooking oil can cut global warming pollution by 80 to 90 percent relative to conventional diesel fuel.

Biodiesel made from unused cooking oil— soy, canola, or palm oil— is a less attractive option because it expands the global market for vegetable oil, a major driver of deforestation.

Unintended impacts of biodiesel

Production of biodiesel from sustainable low carbon sources like used cooking oil is an important and growing oil saving solution.

Unfortunately, policy-driven demand for biodiesel is exceeding the limited supply of low-carbon biodiesel sources, diverting vegetable oils from food markets and other uses.

Shifting these resources to biodiesel production creates a supply gap in food markets that’s then filled by palm oil—and that’s a problem. The production of palm oil destroys rainforests, causing severe social and environmental damage in Southeast Asia and the global climate.

The path forward: prioritize low-carbon biodiesel

Using biodiesel made from recovered waste streams is a smart way to help reduce our oil use. But increasing biodiesel production beyond the availability of these resources causes severe problems.

These problems can be avoided by federal and state policies that ensure biodiesel demand does not exceed the availability of low carbon biodiesel sources.

Otherwise we risk sourcing biodiesel from dirty sources, undermining the potential of biodiesel as an oil saving solution.

Biodiesel versus gasoline in cars and light trucks

For conscientious consumers who already own a diesel vehicle, filling up with biodiesel may reduce your overall global warming emissions, especially if your biodiesel supplier is focused on waste resources.

Keep in mind, however, that biodiesel and gasoline are not interchangeable fuels, and each carries their own advantages and disadvantages.

If you are purchasing a new vehicle, consider a hybrid or electric vehicle to save on fuel costs and minimize global warming pollution.

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