Biodiesel is a domestically made renewable fuel that can be manufactured from a variety of sources. It can be made from new and used vegetable oils, animal fats, or recycled restaurant grease. Biodiesel meets both the biomass-based diesel and overall advanced biofuel requirement of the Renewable Fuel Standard.
It has similar properties to petroleum diesel, but it's a cleaner-burning renewable alternative. Biodiesel is a liquid fuel often referred to as B100 or neat biodiesel in its pure, unblended form. Like petroleum diesel, biodiesel is used to fuel compression-ignition engines.
The Basics
The Basics
Biodiesel is a renewable, biodegradable fuel manufactured domestically from vegetable oils, animal fats, or recycled restaurant grease. Biodiesel meets both the biomass-based diesel and overall advanced biofuel requirement of the Renewable Fuel Standard. Renewable diesel is distinct from biodiesel.
Biodiesel is a liquid fuel often referred to as B100, pure, or neat biodiesel in its unblended form. Like petroleum diesel, biodiesel is used to fuel compression-ignition engines. See the table below for biodiesel's physical characteristics.
Biodiesel performance in cold weather depends on the blend of biodiesel, the feedstock, and the petroleum diesel characteristics. In general, blends with smaller percentages of biodiesel perform better in cold temperatures. Typically, No. 2 diesel and B5 (up to 5% biodiesel) perform about the same in cold weather. Both biodiesel and No. 2 diesel have some compounds that crystallize in very cold temperatures. In winter weather, fuel blenders and suppliers combat crystallization by adding a cold flow improver. For the best cold weather performance, users should work with their fuel provider to ensure the blend is appropriate.
| Biodiesel's Physical Characteristics (for B100) | |
|---|---|
| Specific gravity | 0.88 |
| Kinematic viscosity at 40°C, mm2/s | 1.9 to 6.0 |
| Cetane number | 47 |
| Lower heating value, Btu/gal | ˜119,550 |
| Density, lb/gal at 15.5°C | 7.3 |
| Carbon, wt% | 77 |
| Hydrogen, wt% | 12 |
| Oxygen, by dif. wt% | 11 |
| Boiling point, °C | 330-357 |
| Flash point, °C | 130 |
| Sulfur, % mass (ppm) | 0.0015-0.05 |
| Cloud point, °C | -3 to 15 |
| Pour point, °C | -5 to 10 |
Benefits and Considerations
Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel improves public health and the environment, provides safety benefits, and contributes to a resilient transportation system.
Public Health and the Environment
The transportation sector is the largest source of greenhouse gas emissions in the United States. A successful transition to clean transportation will require various vehicle and fuel solutions and must consider life cycle emissions. Engines manufactured in 2010 and later must meet the same emissions standards, whether running on biodiesel, diesel, or any alternative fuel. Selective catalytic reduction (SCR) technology in diesel vehicles, which reduces nitrogen oxide (NOx) emissions to near-zero levels, makes this possible. The criteria air pollutant emissions from engines using diesel fuel are comparable to those from biodiesel blends.
Using biodiesel reduces life cycle emissions because carbon dioxide released from biodiesel combustion is offset by the carbon dioxide absorbed from growing soybeans or other feedstocks used to produce the fuel. Life cycle analysis completed by Argonne National Laboratory (PDF) found that B100 use reduces carbon dioxide emissions by 74% compared with petroleum diesel. The California Air Resources Board (CARB) reported similar values(PDF) from various sources for its life cycle analysis of biodiesel.
Air quality benefits of biodiesel are roughly commensurate with the amount of biodiesel in the blend. Learn more about biodiesel emissions.