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How is
Biodiesel Used?
There are many ways to
use alkyl esters including as solvents and as
chemical intermediates for the formation of
detergents. However, the application of most
interest to us is as fuel. Fuel applications can be
divided into 3 categories.
1. Pure fuel (B100)
Biodiesel can be used in its pure form, also known
as neat biodiesel, or B100. This is the
approach that provides the most reduction in exhaust
particulates, unburned hydrocarbons, and carbon
monoxide. It is also the best way to use biodiesel
when its non-toxicity and biodegradability are
important. Marine applications may be important for
B100. Although neat biodiesel would not be expected
to cause any operational problems, its solvent
properties will be at their highest intensity and
may cause problems with loosening of varnish
deposits in fuel tanks and lines, degradation of
fuel lines because some elastomers are not
compatible with biodiesel (such as BUNA rubbers),
and paint removal near fuel fill ports. Concrete
can also be degraded if it is subjected to chronic
exposure to biodiesel. These topics will be
discussed later in the section on material
compatibility. B100 will also have the most severe
problems with cold flow properties. These problems
are discussed in detail later in this course.
2. Blends (typically 20-50%)
Biodiesel will blend with petroleum-based diesel
fuel in any proportion so it is common to use blends
of 20 to 50% biodiesel in 80 to 50% No. 2 diesel
fuel. Blends reduce the cost impact of biodiesel
while retaining some of the emissions reduction.
Most of the emissions reductions appear to be
proportional to the percentage of biodiesel used.
The cold flow and solvency problems noted with B100
are less of a concern when blends are used.
3. As an additive, 1-2% (B02)
Tests for lubricity have shown that biodiesel is
a very effective lubricity enhancer. Even as little
as 0.25% can have a measurable impact and 1-2% is
enough to convert a very poor lubricity fuel into an
acceptable fuel. Although these levels are too low
to have any impact on the cetane number of the fuel
or the emissions from the engine, the lubricity
provides a significant advantage at a modest cost.
Other applications:
All three of the applications
described above relate to diesel engines. Biodiesel
has also been considered for use in
spark-ignited engines , but without much
success. Biodiesel is being used in a variety of
non-engine applications such as solvents and paint
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