Biomedical Engineering Reference
In-Depth Information
3.1. Fatty Acid Content
The fatty acid content of the feedstock is one of the most important physical properties
used in choosing. Different feedstock will have varying types of fatty acids that vary in terms
of chain length and degree of saturation. Table 7 shows the dominant fatty acid contents of
common vegetable oils. The effect of chain length and degree of saturation will be discussed
later.
Additionally, when using conventional production methods, feedstocks with minimal
(less than 1%) FFA content is necessary or else expensive pre-treatment must be included in
process design. Free fatty acids are any fatty acids that are not part of a triglyceride. The
following table shows the typical FFA content of the different types of biodiesel feedstock.
As FFA content increases, cost of the feedstock decreases. For example, trap grease is very
cheap, and often restaurants will pay to have them removed, but they require intensive pre-
treatment.
Table 6. Fatty acid composition of crude Jatropha curcas oil
Fatty acid
Formula
Structure
Wt%
Myristic
C
14
H
28
O
2
14:0
0-0.1
Palmitic
C
16
H
32
O
2
16:0
14.1-15.3
Palmitoleic
C
16
H
30
O
2
16:1
0-1.3
Stearic
C
18
H
36
O
2
18:0
3.7-9.8
Oleic
C
18
H
34
O
2
18:1
34.3-45.8
Linoleic
C
18
H
32
O
2
18:2
29.0-44.2
Linolenic
C
18
H
30
O
2
18:3
0-0.3
Arachidic
C
20
H
40
O
2
20:0
0-0.3
Behenic
C
22
H
44
O
2
22:0
0-0.3
Table 7. Fatty acid content of various oils (wt%)
Myristic
(C14:0)
Palmitic
(C16:0)
Stearic
(C18:0)
Oleic
(C18:1)
Linoleic
(C18:2)
Safflower
6.4-7.0
2.4-29
9.7-13.8
75.3-80.5
Canola
4-5
1-2
55-63
20-31
Coconut
13-18.5
7.5-10.5
1-3
5-8.2
1-2.6
Olive
1.3
7-18.3
1.4-3.3
55.5-84.5
4-19
Palm
0.6-2.4
32-46.3
4-6.3
37-53
6-12
Peanut
0.5
6-12.5
2.5-6
37-61
13-41
Rapeseed
1.5
1-4.7
1-3.5
13-38
9.5-22
Soybean
2.3-11
2.4-6
22-30.8
49-53
Sunflower
3.5-6.5
1.3-5.6
14-43
44-68.7
Tallow
3-6
25-37
14-29
26-50
1-2.5
Recycle oil
1-3
13-25
5-12
43-52
7-22
