Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
• 2.3 Biodiesel
Overview
Biodiesel is a nontoxic and biodegradable liquid fuel that is made from renewable
feedstock such as new and used vegetable oils and animal fats. Biodiesel’s properties are
similar to petroleum diesel, but it is generally cleaner burning with notably lower PM and
SO x emissions (Radich, 2004). Given the very small number of light-duty diesel vehicles in
operation in the United States, the following analysis assumes biodiesel use in mediumand
heavy-duty vehicles, although similar benefits would accrue in light-duty applications
as well.
Biodiesel can be blended with petroleum diesel in any percentage, with B20 (20 percent
biodiesel and 80 percent petroleum diesel) commonly discussed in the literature.
However, although some engine manufacturers have approved the use of biodiesel blends
of 20 percent or higher, most manufacturers have not officially approved the use of blend
levels above B5 (National Biodiesel Board, 2009). Use of higher biodiesel concentrations,
especially above B20, may require minor vehicle modifications (e.g., for fuel system seals)
as biodiesel is a stronger solvent than gasoline (Congressional Research Service, 2005). For
this reason blends of B20 and lower are the most common focus in biodiesel research and
testing. As of June 2004, 628 refueling stations offered B20 or higher blends of biodiesel for
sale in the United States (U.S. DOE, 2009b).
Some marine applications also are using biodiesel. In 2006, the National Oceanic and
Atmospheric Administration (NOAA) implemented the Green Ship Initiative, which
converted all research vessels in the Great Lakes region to B100 biodiesel derived from soy.
The conversion included propulsion and auxiliary diesel engines for generating electricity.
NOAA documented higher lubricity and cleaner injectors with the use of biodiesel
compared with marine distillate.
The majority of current U.S. biodiesel production (90 percent) comes from soybean oil,
although many other feedstock can be used, including other plant oils such as canola,
cottonseed, peanut oil, and rapeseed oil; waste vegetable oils (yellow grease); and animal
fat (beef tallow, pork lard). Like corn for ethanol, biodiesel demand for these feedstock
competes with food use. Algae also has long-term potential as a biodiesel feedstock,
although algae production processes are still in the research and development phase (see
sidebar on page 2-45).
The production process for biodiesel is straightforward with relatively low start up costs
(NGA, no date). The ease of start up, along with increasing demand, has resulted in rapid
growth in the U.S. biodiesel industry in recent years, with production tripling from 2004 to
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