Microalgae are currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gal/acre/year) in comparison to current terrestrial feedstocks. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. Moreover, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value, thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 and 6 h, respectively. Tests were conducted at a temperature of 110 °C and airflow of 10 l/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0% to 100% LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45% to 65% of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability.

References

References
1.
Chisti
,
Y.
, 2007, “
Biodiesel From Microalgae
,”
Biotechnol. Adv.
,
25
(
32
), pp.
294
306
.
2.
Demirbas
,
A.
, 2007, “
Importance of Biodiesel as Transportation Fuel
,”
Energy Policy
,
35
(
9
), pp.
4661
4670
.
3.
U.S. Biodiesel Board, 2009, “
U.S. Biodiesel Production Capacity
,” National Biodiesel Board.
4.
Van Gerpen
,
J. H.
,
Pruszko
,
R.
,
Clements
,
D.
, and
Shanks
,
B.
, 2006, “
Building a Successful Biodiesel Business
,” 2nd ed., Biodiesel Basics, Dubuque, IA.
5.
Knothe
,
G.
,
Dunn
,
R. O.
, and
Bagby
,
M. O.
, 1997, “
Biodiesel: The Use of Vegetable Oils and Their Derivatives as Alternative Diesel Fuels
,”
Fuels and Chemicals From Biomass
,
Saha
,
B. C.
, and
Woodward
,
J.
eds.,
American Chemical Society
,
Washington, DC
, pp.
172
208
.
6.
Ramos
,
M. J.
,
Fernández
,
C. M.
,
Casas
,
A.
,
Rodríguez
,
L.
, and
Pérez
,
A.
, 2009, “
Influence of Fatty Acid Composition of Raw Materials on Biodiesel Properties
,”
Bioresour. Technol.
,
100
(
1
), pp.
261
268
.
7.
Hu
,
Q.
,
Sommerfeld
,
M.
,
Jarvis
,
E.
,
Ghirardi
,
M.
,
Posewitz
,
M.
,
Seibert
,
M.
, and
Darzins
,
A.
, 2008, “
Microalgal Triacylglycerols as Feedstocks for Biofuel Production: Perspectives and Advances
,”
Plant J.
,
54
(
4
), pp.
621
639
.
8.
Roncarati
,
A.
,
Meluzzi
,
A.
,
Acciarri
,
S.
,
Tallarico
,
N.
, and
Melotti
,
P.
, 2004, “
Fatty Acid Composition of Different Microalgae Strains (Nannochloropsis sp., Nannochloropsis oculata (Droop) Hibberd, Nannochloris atomus Butcher and Isochrysis sp.) According to the Culture Phase and the Carbon Dioxide Concentration
,”
J. World Aquaculture Soc.
,
35
(
3
), pp.
401
411
.
9.
Greenwell
,
H. C.
,
Laurens
,
L. M. M.
,
Shields
,
R. J.
,
Lovitt
,
R. W.
, and
Flynn
,
K. J.
, 2010, “
Placing Microalgae on the Biofuels Priority List: A Review of the Technological Challenges
,”
J. R. Soc. Interface
,
7
(
46
), pp.
703
726
.
10.
Knothe
,
G.
, and
Dunn
,
R. O.
, 2003, “
Dependence of Oil Stability Index of Fatty Compounds on Their Structure and Concentration and Presence of Metals
,”
J. Am. Oil Chem. Soc.
,
80
(
10
), pp.
1021
1026
.
11.
Durrett
,
T. P.
,
Benning
,
C.
, and
Ohlrogge
,
J.
, 2008, “
Plant Triacylglycerols as Feedstocks for the Production of Biofuels
,”
Plant J.
,
54
(
4
), pp.
593
607
.
12.
Graboski
,
M. S.
, and
McCormick
,
R. L.
, 1998, “
Combustion of Fat and Vegetable Oil Derived Fuels in Diesel Engines
,”
Progress Energy Combust. Sci.
,
24
(
2
), pp.
125
164
.
13.
Karavalakis
,
G.
,
Karonis
,
D.
, and
Stournas
,
S.
, 2009, “
Evaluation of the Oxidation Stability of Diesel/Biodiesel Blends Using the Modified Rancimat Method
,”
SAE Int. J. Fuels Lubricants
,
2
(
1
), pp.
839
849
.
14.
Knothe
,
G.
, 2007, “
Some Aspects of Biodiesel Oxidative Stability
,”
Fuel Process. Technol.
,
88
(
7
), pp.
669
677
.
15.
McCormick
,
R. L.
,
Ratcliff
,
M.
,
Moens
,
L.
, and
Lawrence
,
R.
, 2007, “
Several Factors Affecting the Stability of Biodiesel in Standard Accelerated Tests
,”
Fuel Process. Technol.
,
88
(
7
), pp.
651
657
.
16.
Knothe
,
G.
, 2010, “
Biodiesel: Current Trends and Properties
,”
Topics Catal.
,
53
(
11–12
), pp.
714
720
.
17.
Van Gerpen
,
J. H.
,
Hammond
,
E. G.
,
Yu
,
L.
, and
Monyem
,
A.
, 1997, “
Determining the Influence of Contaminants on Biodiesel Properties
,” SAE Paper No. 971685.
18.
McCormick
,
R. L.
, and
Westbrook
,
S. R.
, 2010, “
Storage Stability of Biodiesel and Biodiesel Blends
,”
Energy Fuels
,
24
(
1
), pp.
690
698
.
19.
Knothe
,
G.
, 2002, “
Structure Indices in FA Chemistry: How Relevant is the Iodine Value?
,”
J. Am. Oil Chem. Soc.
,
79
(
9
), pp.
847
854
.
20.
Jain
,
S.
, and
Sharma
,
M. P.
, 2010, “
Stability of Biodiesel and Its Blends: A Review
,”
Renew. Sustain. Energy Rev.
,
14
(
2
), pp.
667
678
.
21.
Dunahay
,
T. G.
,
Jarvis
,
E. E.
,
Dais
,
S. S.
, and
Roessler
,
P. G.
, 1996, “
Manipulation of Microalgal Lipid Production Using Genetic Engineering
,”
Appl. Biochem. Biotechnol.
,
57–58
(
1
), pp.
223
231
.
22.
Sheehan
,
J.
,
Dunahay
,
T.
,
Benemann
,
J.
, and
Roessler
,
P.
, 1998, “
A Look Back at the US Department of Energy’s Aquatic Species Program: Biodiesel From Algae
,” National Renewable Energy Laborary, Golden, CO, NREL/TP-580-24190, http://www.nrel.gov/docs/legosti/fy98/24190.pdf
23.
Mata
,
T. M.
,
Martins
,
A. A.
, and
Caetano
,
N. S.
, 2010, “
Microalgae for Biodiesel Production and Other Applications
,”
Renew. Sustain. Energy Rev.
,
14
(
1
), pp.
217
232
.
24.
Williard
,
D. E.
,
Kaduce
,
T. L.
,
Harmon
,
S. D.
, and
Spector
,
A. A.
, 1998, “
Conversion of Eicosapentaenoic Acid to Chain-Shortened Omega-3 Fatty Acid Metabolites by Peroxisomal Oxidation
,”
J. Lipid Res.
,
39
, pp.
978
986
.
25.
Martek Biosciences Corporation, 2009, accessed: November 11, 2011, http://www.lifesdha.com/Finding-lifesDHA-/Partner-Products/tabid/129/Default.aspx
26.
U.S. Department of Energy, 2010, “
National Algal Biofuels Technology Roadmap
,” DOE Biomass Program, http://www1.eere.energy.gov/biomass/pdfs/algal_biofuels_roadmap.pdf
27.
Karavalakis
,
G.
, and
Stournas
,
S.
, 2010, “
Impact of Antioxidant Additives on the Oxidation Stability of Diesel/Biodiesel Blends
,”
Energy Fuels
,
24
(
6
), pp.
3682
3686
.
28.
ASTM Standard D675, 2009, “Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels
,” ASTM International, West Conshohocken, PA.
29.
British Standards Institution, 2003, “
Fat and Oil Derivatives. Fatty Acid Methyl Esters (FAME). Determination of Oxidation Stability (Accelerated Oxidation Test)
,” BSI, London, BS EN 14112:2003.
30.
Fisher
,
B. C.
,
Marchese
,
A. J.
,
Volckens
,
J.
,
Lee
,
T.
, and
Collett
,
J. L.
, 2010, “
Measurement of Gaseous and Particulate Emissions From Algae-Based Fatty Acid Methyl Esters
,”
SAE Int. J. Fuels Lubr.
,
3
(
2
), pp.
292
321
.
31.
Benamotz
,
A.
,
Tornabene
,
T. G.
, and
Thomas
,
W. H.
, 1985, “
Chemical Profile of Selected Species of Microalgae With Emphasis on Lipids
,”
J. Phycol.
,
21
(
1
), pp.
72
81
.
You do not currently have access to this content.