Biodiesel Properties and Applications



Properties


Biodiesel or methy esters are a vegetable oil or animal fat based fuel. Biodielse is produced using a chemical process called transesterfication, where methonal or another alcohol is added to the vegetable oil which produces byproducts of biodiesel and glycerin. Transesterfication reactions convert one type of ester into another ester; this reaction is usually catalyzed by an acid or base. Vegetable oils and animal fats consist of triglyceride molecules; the mono-alkylesters of triglycerides are used as the fuel in biodiesel. (ref 1)

Fat_triglyceride_shorthand_formula.png
http://en.wikipedia.org/wiki/File:Fat_triglyceride_shorthand_formula.PNG

Transesterification Process to produce biodiesel is shown below.
(ref 2)


bond51.gif
http://www3.me.iastate.edu/biodiesel/Pages/biodiesel3.html

Triglyceride + methanol -------> mixture of fatty esters + glycerol





Basic Properties of Biodiesel (B100) (ref 3)
Property
Value
Unit

Heating Value or Calorific Value

118,296

BTU/gal


Boiling Point

315

°C


Vapor Pressure

<1

mmHg


Flash Point

218

°C


Specific Gravity

0.87

mg/L


Melting Point

-1

°C


Solubility

Negligible in Water





No. 2 Diesel has a heating value of approximately 129,000 BTU/gal, which about 8-11% more than biodiesel. Material compatibility of biodiesel is a concern with using pure diesel in some conditions and applications. Gelling or thickening is common when biodiesel is exposed to colder temperatures (< 14 - 61 °F) depending on the origin of the biodiesel and its chemistry. There are admixtures developed and being refined to lower the gelling point. The use of two fuel tanks, one with petrodiesel (#2 Diesel) and the other with biodiesel, allow the vehicle to start using the petrodiesel and warm the biodiesel for consumption. Blends of petrodiesel and biodiesel such as B20 also are subject to gelling and create operation concerns in diesel vehicles. Water absorption is a concern when storing biodiesel and exposing it to the atmosphere. Biodiesel is a hygroscopic, which means it can absorb water from atmospheric moisture. The absorption of water can be reduced during production by adding addition methanol to insure a complete reaction. Biodiesel is also incompatible with oxygen and strong oxidizers such as chlorates, nitrates and peroxides.

Biodiesel’s most important property is that it is biodegradable, non-toxic and free of sulfer and aromatics. This allows the biodiesel to be safely handled and transported.

Negative characteristics of biodiesel are that it releases a larger amount of NOx, which can lead to increases in photochemical smog in industrial and high traffic areas, than petrodiesel (No. 2 Diesel).

Applications


There are many uses for biodiesel and more applications currently being researched to provide a sustainable fuel for the future. Biodiesel can be used in:
  1. vehicles (cars, trucks, buses, agricultural applications, and off-road/construction applications)
  2. airplanes
  3. trains
  4. marine equipment
  5. heating oil
  6. blends of fuel
Other applications include replacement of conventional and synthetic motor oil and other lubricants.

Biodiesel Vehicles
Vehicles with conventional unmodified diesel engines do not require modification to consume biodiesel, but problems arise when biodiesel is used. Vehicle manufacturers have been able to design modified engines to reduce some of side effects of running on biodiesel, which include fuel filter plugging, carbon deposits in the fuel injector, piston ring malfunction, seal breakage, and fuel line breakage. These effects are caused by gelling or crystallizing of biodiesel which do not allow it to be filtered or pumped. Soy methyl esters typically begin to gel and/or crystallize at temps of 22 °F; No. 2 Diesel has a gelling point of 1 °F.

Marine Applications
The use of B100, pure biodiesel, is very favorable in marine applications since biodiesel is non-toxic and biodegradable.

Fuel Blends
Blends comprised of biodiesel are designated as Bxxx, where the xxx can range from 100 to 0.01 percent of biodiesel. Blends are more favorable for use in commercial and domestic vehicles because it has a substantial impact on reducing emissions and also reduce the negative impacts of cold temperatures on biodiesel.
John Deere, agricultural equipment manufacturer, has been building and promoting (see video)(ref 4) the use of biodiesel blends in their equipment. They have developed a fuel conditioner that can be used in fuels with a B20 or higher grade to avoid adverse effects.

Below is chart that “shows data for the cold flow properties of biodiesel and blends of biodiesel with diesel fuel. The cloud point is the temperature at which crystals first start to form in the fuel and the pour point is the lowest temperature at which the fuel will still pour from a container. The cold filter plugging point (CFPP) is the lowest temperature at which at certain volume of fuel can be drawn through a metal screen filter. It usually correlates well with the lowest temperature that an engine will operate.”(ref 5)




Cloud Point (oF)
Pour Point (oF)
CFPP(oF)
Soy Methyl Esters (soy)
32
25
22
Yellow Grease Methyl Esters (YG)
48
45
48
#2 low Sulfur Diesel Fuel (#2)
4
-30
1
2% Soy in #2
6
-25
1
5% Soy in #2
8
-20
-1
2% YG in #2
6
-25
0
5% YG in #2
9
-20
1
50% #2 / 50% #1 (50/50)



-6
-45
-12
2% Soy in 50/50
-6
-40
-14
5% Soy in 50/50
-6
-40
-14
2% YG in 50/50
-6
-40
-12
5% YG in 50/50
-2
-30
-10
#1 Low Sulfur Diesel Fuel (#1)
-54
-70
< -30
2% Soy in #1
-45
-60
< -30
5% Soy in #1
-32
-55
< -30
2% YG in #1
-38
-60
< -30
5% YG in #1
-19
-60
-26



----

1. http://en.wikipedia.org/wiki/File:Fat_triglyceride_shorthand_formula.P
2. http://www3.me.iastate.edu/biodiesel/Pages/biodiesel3.html
3. http://www.mae.carleton.ca/MSDS/biodiesel.pdf
4. http://www.deere.com/en_US/rg/infocenter/biodiesel/what_biodiesel_means/index.html
5. http://www3.me.iastate.edu/biodiesel/Pages/biodiesel9.html