1. Extraction and Conversion of Algal Biomass under Supercritical Conditions
P.Patila, H. Readya, T. Muppanenia, S.Denga, T.Schuabb, Peter Cookec, N. Khandand , P. Lammerse
Chemical Engineering Department a
Chemical Analysis and Instrumentation Laboratory b
Electron Microscopy Laboratory c
Civil and Environmental Engineering Department d
Energy Research Laboratory e
Las Cruces, NM ,USA
NAABB Upstream-Downstream Final Meeting, Phoenix, AZ, Jan 22- Jan 24, 2013

2. Outline Supercritical MeOH/EtOH Conversion Process for Wet Algae
Microwave-mediated Transesterification of Wet Algal Biomass to Biodiesel under Supercritical Ethanol Conditions
Supercritical CO2 Extraction of Algal Lipids
Subcritical Water Extraction of Algal Lipids
Supercritical Methyl Acetate Process for Algal Biodiesel

3. Supercritical Conversion
Supercritical Fluids
Supercritical Conversion Benefits
No catalyst is needed, short reaction time (<60 min.)
Temp. is the most important process parameter
Pressure affects conversion rate
High alcohol/oil ratio facilitates conversion
Water (60%) don’t affect SCF conversion
Small amount of water helps the conversion
Conversion rate is faster in SCF than sub-critical
High dissolving power (103 – 106 > liquid solvents)
Low viscosity
High diffusivity
Easy separation
No harmful solvents
Selective extraction/separation
Suitable for food/medicine active ingredients
CO2, H2O, CH3OH ….
Pinnarat and Savage, Ind. Eng. Chem. Res., 47: (2008) 3

4. Elemental and Fatty Acid Composition of Nannochloropsis Salina
Elements
Wt. (%)
Carbon (C)
70.43
Oxygen (O)
22.19
Sodium (Na)
0.74
Magnesium (Mg)
1.16
Phosphorous (P)
2.42
Chlorine (Cl)
0.36
Potassium (K)
1.32
Calcium (Ca)
0.94
Sulfur (S)
0.34
Total Lipid Content in algal Biomass : 50-55% on Dry Basis
Fatty acids
Wt. %
Tetradecanoic acid, C14:0
2.72
Hexadecanoic acid, C16:0
37.83
Hexadecenoic acid, C16:1 n7
31.34
Octadecanoic acid, C18:0
5.63
cis-9-Octadecanoic acid, C18:1 n9
11.31
cis-11,14-Eicosandienoic acid, C20:2 n6
1.3
cis-5,8,11,14-Eicosatetraenoic acid, C20:4 n6
2.24
cis-5,8,11,14,17-Eicosapentaenoic acid, C20:5 n3
6.35
Total fatty acids
Saturated fatty acids
45.69
Unsaturated fatty acids
54.31

5. Direct Conversion of Wet Algae to Biodiesel under SCM
Optimal conditions:1:9 (wt./vol.) MeOH ratio, around 255 ºC & 25 min.
Crude algal biodiesel
Pure algal biodiesel
Parr Micro-Reactor
Patil, P.D., et al. Optimization of direct conversion of wet algae to biodiesel under supercritical methanol conditions. Bioresour. Technol. (2011),102(1), 5

6. Wet Algae to Biodiesel under Supercritical Ethanol (SCE)
Experimental :
3 g of wet algae paste (40% solids); Reaction times:2-30 min; Reaction temperatures C; and wet algae to ethanol (wt./vol.) ratios : 1:6-1:15.
TGA Analysis of Wet Algae:
Dehydration: C
Thermal Degradation : C
Decomposition (Fast Pyrolysis): C
Single-step conversion of wet algal biomass to biodiesel was demonstrated.
Saves large amount of energy consumed during harvesting & drying.
Completely renewable sources of energy such as algae and ethanol used for “Green” biodiesel.
Harvind Reddy et al. Direct conversion of wet algae to biodiesel under supercritical ethanol conditions. Applied Energy (Under Review) 6

7. Microwave-Mediated Supercritical Transesterification
R1,R2,R3 are Long chian hydrocarbons may be same or different
The microwave effect on the transesterification reaction is twofold: (1) enhancement of reaction by a thermal effect, and (2)
evaporation of ethanol due to the strong microwave interaction of the material. The microwave interaction with the reaction
compounds (triglycerides and ethanol) results in a large reduction of activation energy due to an increased dipolar polarization
Phenomenon and Ionic Conduction yield to FAEE and glycerol. This reaction is Non-catalytic carried out under Supercritical ethanol conditions.
Patil, P.D., et al. Microwave-mediated non-catalytci transesterification of algal biomass under supercritical ethanol conditions. Jour of Supercritical Fluids, 2012.

8. Supercritical CO2 Extraction of Algal Lipid from Dry Alghae
TharSFC Reactor
GC-MS Analysis
Operating range: P : bar
Max T.: 150 ºc ; 2 Lit 8 8

9. Subcritical Water Extraction of Lipids from Algal Biomass
Experimental :
Heating conventional and microwave
Biomass loading % solids); Extraction time :10-30min; Extraction temperatures – oC,
Solvent : Hexane
Optimum conditions for C-SCW extraction:
Extr. temp. 220 oC
biomass load. 7.5 %
Extr. Time 25 min.
Optimum conditions for MW-SCW extraction.:
Extr. temp. 205 oC
biomass load. 25 %
Comparison:
Parr Micro-Reactor
Anton Parr Microwave Reactor
 FAME content in biomass: 24.7% on dry wt. basis
(% dry wt. basis)
Folch Extraction
Conventional -SCW extraction
Microwave -SCW extraction
Avg. Total lipid or Bio-crude extraction
± 1.74
31 ± 1.6
35.7 ± 1.18
FAME content in extracted total lipid or bio-crude extraction (% bio-crude)
40.15 ± 0.59
53.99 ± 2.35
67.10 ± 1.74
Total FAME extracted (% dry wt.)
8.18 ± 0.59
16.75 ± 1.30
24.61 ± 0.33
Subcritical water extracted bio-crude and pure algal oil
Harvind, Patil et al Subcritical water extraction of algal oil from algal biomass . Energy and Environmental science (Under Review) 9

10. Supercritical Methyl Acetate Process for Algal Biodiesel
All Supercritical process produces large quantity of glycerin -----Over Produced ???? ( Big Problems to Commercial biodiesel processes)
Reaction Parameters: Total lipid : 7 ml, Methyl Acetate: 25 ml (1:42 molar ratio) , Time: 120 min, Temperature: 280 C, Pressure: 1178 psi (~ 81 bar)
Critical Properties of Methyl acetate : C, 45.9 bar, Sp.G , Mol wt: 74, Boiling pt at 1 atm- 57 C,
Triacetin BP: C
A mixture of fatty acid methyl esters and triacetin found to be used as biodiesel and can enhance its oxidation stability and fuel properties
since the obtained triacetin is miscible with fatty acid methyl esters, both products can readily be used as biodiesel.
Crude Biodiesel Fuel (FAME + Triacetin) yield ~ %
Apparent FAME
yield ~ 80%

11. Elemental and Fuel Properties of Algal Extracts
Analysis
Samples
SCCO2 crude lipid
SCCO2 pure algal oil
SCW
crude lipid
Pure algal oil
SCMA
Algal biodiesel
SCM
Algal
Biodiesel
% Carbon (C)
75.09
76.40
76.75
78.20
74.69
78.12
ASTM D5373
% Hydrogen (H)
11.16
11.71
11.11
11.93
11.50
D5373
% Nitrogen (N)
0.46
0.03
0.96
0.18
0.05
D5291
% Oxygen (O)
12.99
11.89
11.20
9.53
13.78
9.91
D5622
% Sulfur (S)
0.09
0.02
0.11
0.04
D1558
Fuel Properties
Fuel property
1st generation biodiesel (Corn Biodiesel)
Algal SCM biodiesel
Diesel
ASTM D6751 biodiesel standard
HHV (MJ/kg)
40-45
41-43
45.9
---
Kinematic Viscosity (mm2/s)
3- 5.2
Density
Pour point
-15 to 10
-12 to -10
-35 to -15

12. Proposed Scale-up Technologies
Integrated SCM to produce algal biodiesel and power cogeneration
Integrated algal biodiesel SCM production facility with anaerobic digestion of LEA

13. Summary of Accomplishments
PUBLICATIONS in Peer-Reviewed Journals
P.Patil , S.Deng et al. Power Dissipation In Microwave-Enhanced In-situ Transesterification of Algal Biomass Green Chemistry 2012,14,
P.Patil,, S.Deng et al. Comparison of direct transesterification of algal biomass under supercritical methanol and microwave irradiation conditions. Fuel 2011, 97,
P.Patil, , S.Deng et al. Direct Conversion of Wet Algal Biomass to Biodiesel under Supercritical Methanol Conditions. Bioresource Technology 2011, 102,
P.Patil, S.Deng et al. Optimization of microwave-assisted transesterification of dry algal biomass using response surface methodology. Bioresource Technology 2011, 102,
P. Patil, S.Deng et al. Microwave-Mediated Catalyst-Free Transesterification of Algal Biomass under Supercritical Ethanol Conditions, J of Supercritical Fluids, 2012.
P. Patil, S.Deng et al. In-Situ Biodiesel Production from Algal Biomass under Microwave-Mediated Supercritical Ethanol Conditions. Environmental Science & Tech (Revised)
H Reddy, P.Patil, S. Deng et al. Direct conversion of wet algae to biodiesel under supercritical ethanol conditions. Applied Energy (Review).
H Reddy, P.Patil, S. Deng et al. Subcritical Water Extraction of Lipids from Wet Algal Biomass to Produce Biofuels. Energy & Environmental Science ( Review)
PATENTS PENDING
Deng S., Patil Prafulla, Gude Veera. “Optimization of microwave-assisted transesterification of dry
algal biomass using response surface methodology”. US Patent- 61/426,305 (Filed: December 22,
2010).
Deng S., Patil Prafulla, Gude Veera. “Direct Conversion of Wet Algal Biomass to Biodiesel under
Supercritical Methanol Conditions”. US Patent- 61/426,333 (Field: Dec’22, 2010).

14. Concluding Remarks
SCM and SCE for wet algal biomass can potentially be an energy efficient and economical route for algal biodiesel production.
MW-SCE process improves extractions of algae significantly, with a higher efficiency, reduced extractive-transesterification time and increased yield.
An ecofriendly green (subcritical water) extraction process was developed and achieved maximum efficiencies with wet algal biomass
SC-CO2 is cleaner production technology (chemically stable, non-toxic, non-flammable) for extraction of algal lipids/oils for algal biodiesel production.
Microwave-pretreatment prior to SCCO2 with Azeotropic co-solvents (Hexane+ Ethanol) process gives high quality microalgae oil, rich in fatty acids and increases lipid yield with better recovery of TAG’s.
Supercritical methyl acetate process could be the next-generation technology for algal biodiesel production. 14 14

15. Acknowledgements
The (authors) would like to acknowledge funding of this work by the US Department of Energy under contract DE-EE awarded to the National Alliance for Advanced Biofuels and Bioproducts 15 15