Progress and Perspectives of Large Scale Algae Biomass Harvesting: A Case Study at the ATP 3 Testbed

Transcription

1 Progress and Perspectives of Large Scale Algae Biomass Harvesting: A Case Study at the ATP 3 Testbed Xuezhi Zhang, John McGowen, Milton Sommerfeld and Pierre Wensel Arizona Center for Technology and Innovation (AzCATI) Arizona State University Sep 29 Oct 2, Algae Biomass Summit, San Diego

2 Outline Introduction Challenges in algae harvesting Progress of large scale algae harvesting Algae harvesting using membrane filtration Algae harvesting using sedimentation and DAF Algae harvesting using centrifugation Techno- economic model analysis for large scale algae harvesting Perspectives of large scale algae harvesting Influence of the algae cell surface properties and media characteristics on the algae harvesting using flotation Growth inhibition of culture media recycling Qualities of the harvested biomass

3 Production of Algae Biomass, Biofuels and Bioproducts CO 2 Nutrients Water Biodiesel Cultivation Harvesting Pharmaceutical/ Nutraceutical Bioproducts Extraction/conversion

4 Challenges in Algae Harvesting -Huge volume of water needs to be processed for one gallon biodiesel Parameter Value Algae concentration (g L -1 ) 1 Oil content (%) 3% Neutral lipid (%) 5% Extract efficiency (%) 8% Biodiesel density (g L -1 ) 9 Algae dry biomass (kg) 28.4 Water volume needed (L) 28,388 -Difficult to separate algae from water Similar density to water (11-13 kg m -3 ) Small size (2-5 µm diameters) Diversity of algal cell and culture medium characteristics 4

5 Algal Mass Cultivation at the ATP 3 Testbed 1,5 L each 66 L each 15, L, L

6 Algae Harvesting and Dewater Technologies at the ATP 3 Testbed Sedimentation Dissolved air flotation G Membrane filtration Centrifugation Freeze dryer

7 Algae Harvesting using Membrane Filtration Before Harvesting Algae Concentrate Filtrate Membrane algae harvesting unit (Litree) Feed, concentrate and permeate collected for membrane harvesting Photobioreactor Membrane CO 2 Q C, c water Q, ρ i, X i ρ, X ρ, X Permeate Q-Q H, ρ e, X e RQ ρ H, X H Q D Q H Pore size: ~1 nm

8 SEM Images of Clean and Fouled Membrane Clean membrane After algae cake layer buildup Absorbance Absorbance Fouled membrane C-OH Polysaccharides C-N C=O -NH Virgin membrane Wave number (cm -1 ) Zhang et al. Algal Research 213

9 Optimize Operation Conditions of Membrane Harvesting Air assisted backwashing with air scouring Hollow fiber (inside out) Flux (L m -2 h -1 ) Air assisted backwash with air scour Air assisted backwash without air scour Operation optimization Flux (L m -2 h -1 ) m s -1.9 m s -1.1 m s -1 Algae suspension in fiber Algae cake layer 12 Zhang et al. Separation and Purification Technology 29 Flux (L m -2 h -1 ) Time (min) 1 min 15 min 3 min 6 min Filtration time (min) Flux (L m -2 h -1 ) Time (min) 2 3 NaClO (mg L -1 ) Zhang et al. Bioresource Technology

10 Production Scale Membrane Algae Harvesting Concentrate Permeate Membrane algae harvesting units (Litree) 15, L Recycled culture media Membrane area: 3 m 2 Permeate flow : 19 L/m 2 h Biomass recovery: 85% Solid content : 4-6% Medium recycle: 9%

11 Modeling of Membrane Algae Harvesting 12 Experimental Model Flux (L m -2 h -1 ) Zhang et al. Bioresource Technology Filtration time (min)

12 Algae Harvesting using Sedimentation d p, ρ p, N p d f, ρ f, v f, N f Lamella Before Harvesting Algae Concentrate Effluent Sedimentation algae harvesting unit (Integrated Engineers) Flow rate: 5-8 gpm Biomass recovery: 8% Solid content: <3%

13 Algae Harvesting using Dissolved Air Flotation d fb, ρ fb, v fb, N fb d p, ρ p, N p d f, ρ f, v f N f d b, ρ b, v b, N b DAF algae harvesting unit (World Water Works) Flow rate: 3-5 gpm Biomass recovery: ~75% Solid content: 6-8%

14 Algae Harvesting using Dissolved Air Flotation Solid content (%) Dry weight in residual (g L -1 ) Time (min) Algae Concentration in the DAF Effluent Harvested 7% Settled 4% Effluent 13% Penetrate screen 4% Other 9%. Pond Before screen Final product Solid Contents of DAF Harvested Algae Biomass Biomass mass balance

15 Algae Harvesting using Dynamic Settler/Evodos Centrifuge Scenedesmus sp. Separation Efficiency (%) Evodos centrifuge Scenedesmus sp., Pond Chlorella sp., Pond Nannochloropsis sp., Pond Nannochloropsis sp. PBR Flow rate (L/h) Evodos Centrifuge Chlorella sp. Nannochloropsis sp.

16 Techno- economic Model Analysis for Large Scale Algae Harvesting Input algae characteristics Input goal, VRF or time Harvesting technologies & key parameters Calculate efficiency, cost Optimized harvesting process

17 Summary of Algae Harvesting Technologies Parameters Sedimentation Dissolved Air Table Title flotation Process illustration Membrane Filtration Centrifugation G Concentration factor <15 1~3 5~2 > Separation efficiency >9% >85% ~% >8% Biomass recovery ~8% ~75% ~85% ~75% Solid content of harvested biomass Readiness of culture medium reuse Quality of algae biomass harvested <3% 6-8% 4-6% >2% Need treatment Coagulant contamination further Need treatment Coagulant contamination further Ready to reuse Need further treatment No contamination No contamination Cells may break Based on the harvesting of Nannochlorpsis sp, with a process flow of 5 L/h

18 Harvesting Efficiency (%) Harvesting efficiency (%) Perspectives of large scale algae harvesting - 1) Factors Affecting DAF Algae Harvesting Influence of algal species Al 3+ (mg g -1 ) Influence of coagulant Haematococcus sp. Scenedesmus sp. Chlorella sp. Chitosan Al 3+ Fe 3+ CTAB Coagulant / Algae Dry Weight (mg g -1 ) Harvesting efficiency (%) Influence of growth phases Exponential phase Stationary phase Declining phase Al 3+ /Algae dry weight (mg g -1 )

19 Characterize Algal Cell Surface Functional Groups at Different Growth Phases of Chlorella sp..5 A Exponential Stationary Declining ph M NaOH (ml) Concentration (mmol g -1 ) Carboxyl Phosphate Amine/hydroxyl Culture Time (day) Zhang et al. Bioresource Technology 212

20 Influence of Surface Functional Group on the Harvesting of Chlorella sp. Harvesting efficiency (%) Exponential phase, DOM removed Stationary phase, DOM removed Declining phase, DOM removed Exponential phase Stationary phase Declining phase Al 3+ /Functional group (mg mmol -1 ) Zhang et al. Bioresource Technology 212

21 Dry weight (g/l) Dry weight (g L -1 ) Perspectives of large scale algae harvesting - 2) Reduced Growth in the Recycled Media 64 mg/l Recycled 64 mg/l Fresh mg/l N, fresh 32 mg/l N, recycled Time (d) Time (d) Dry Weight (g L -1 ) Dry Weight (g L -1 ) Fresh, N 64 mg/l Recycled, N 64 mg/ln Time (d) Fresh, N 32 mg/l Recycled, N 32 mg/ln Time (d)

22 Identification of Growth Inhibitors in the Recycled Media 1.2 Absorbence 1. Culture Blank Recycling Culture Wavelength Number, cm Culture Blank Recycled medium 6. EX (nm) Response (mv) Molecular Weight (Dalton) EM (nm)

23 Perspectives of large scale algae harvesting - 3) Quality of Harvested Biomass and Culture Media Harvesting efficiency (%) Mg 2+ Chitosan Al 3+ Fe Coagulant / Algae Dry Weight (mg g -1 ) separated Metal Concentration (mg L -1 ) (a) DAF separated media Ca Mg Al Fe No coagulant Chitosan Mg Al Fe * * Metal Content (mg g -1 ) (b) DAF harvested biomass Ca Mg Al Fe Centrifuge Chitosan Mg Al Fe * * * Metal Content (mg g -1 ) (c) Biomass washed with.1 M HCl Ca Mg Al Fe Centrifuge Chitosan Mg Al Fe *

24 Summary Huge amount of water needs to be processed for algae harvesting. Economic and efficient algae harvesting consist of volume reduction process and dewatering process Algal strain, growth conditions, and the usages of harvested biomass needs to be considered when select the harvesting method Qualities of the harvested biomass, and culture media recycling needs to be considered Techno-economic model helps to guide the selection of algal harvesting technologies.

25 Acknowledgements This work funded in part by DOE Awards EE3372 and EE5996 Dr. Qiang Hu Dr. Milton Sommerfeld Dr. John McGowen Dr. Thomas Dempster Dr. Yongsheng Chen Dr. John Hewson Dr. Mark Edwards Dr. Danxiang Han Dr. Peter Zemke Dr. Wei Chen Dr. Yingchun Gong Dr. Wen Zhang Zixuan Hu Pasquale Amendola Wei Zhang Monica Reynoso Michael Bellefeuille