Growing Duckweed to Recover Nutrients from Wastewater and for Biofuel Production Jay J. Cheng and Anne-M. Stomp NC STATE UNIVERSITY @ Biotechnology Center for Agriculture and Environment Rutgers University December 21, 2009
Municipal Wastewater
Agricultural Wastewater
Global Oil Consumption
Oil Production Prediction
Energy Consumption in US (2005) lion BT TU Qu uadril 120 100 80 60 40 0 101 86 20 8.2 6.6 Total Fossil Fuel Nuclear Renewable
Renewable Energy in US (2005) Qua adrillio on BTU 66 6.6 7 6 5 biomass 4 hydroelectric 33 3.3 3 2.7 2 1 0.34 0.07 0.18 0 total geothermal solar wind
Conversion of Animal Wastewater for Energy Production
Animal Wastewater t High strength wastewater: COD: 4,000 40,000 mg/l TKN: 200 2,000 mg/l Total P: 50 600 mg/l Typical treatment systems: Anaerobic lagoons or digesters Cropland dirrigationi Environmental concerns: Ammonia and other gas emission Potential contamination to water resources Odor emission i
Concept of Systems Approach Biogas Animal Wastewater Anaerobic Effluent Duckweed Pond Cleaner Water Anaerobic Digester Fuel Ethanol Saccharification Fermentation Harvested High-Starch h Duckweed Bioreactor
What is duckweed? Duckweed Fronds Duckweed Pond
Duckweed Size
Why using duckweed? Extremely high hgrowth rate High rate of nutrient (N, P, and minerals) uptake Tolerance to high nutrient levels (e.g. Spirodela polyrrhiza: 1,000 mg/l N & 1,500 mg/l P) Growing at a wide variety of climate conditions High protein (15-45% dry weight) or high starch (up to 70% dry weight) Covering water surface to greatly reduce odor and ammonia emission Easy to harvest
Goal To develop a duckweed-based system for animal wastewater t treatment t t (remove and utilize the nutrients from the wastewater) and dfuel ethanol production
Objectives To identify superior duckweed strains for nutrient recovery from anaerobically treated swine wastewater To determine duckweed nutrient uptake rate, its growth rate, and their relationship To understand the mechanism of nutrient uptake by duckweed and nutrient transport in duckweed pond To investigate the production of high-starch duckweed biomass for fuel ethanol production
Lab Screening Worldwide Collection: > 1,000 Strains Spirodela, Lemna, Wolffia, Wolfiella Maintaining Records Faster Growers: 41 Strains In vitro screening using artificial swine wastewater Highest Protein Producers: 6 Strains: Spirodela puntata (2) Lemna gibba Lemna minor Lemna obscura Lemna aequinoctialis
Greenhouse Selection Highest Protein Producers: 6 Strains: Spirodela dl puntata () (2) Lemna gibba Lemna minor Lemna obscura Lemna aequinoctialis Greenhouse test t using anaerobically treated swine wastewater Three Top Candidates: Spirodela dl puntata 7776 Lemna gibba 8678 Lemna minor 8627
Lab Tests on N and P Removal from Artificial Animal Wastewater by Growing Duckweed
In Vitro Test Duckweed: Spirodela punctata 7776 Lemna minor 8627 Medium: Artificial swine wastewater Temperature: 23 o C Photon flux density: 40 umol/m 2 -s Photoperiod: 16 hours/day
In Vitro Test N Co onc., mg/l 300 250 200 150 100 Spirodela 35 punctata 7776 Nutrient uptake in artificial swine wastewater P Co onc., mg/l Duckwee ed (dry), mg 50 (a) 0 35 (b) 30 25 20 15 10 5 0 1400 1200 1400 (c) Growth Rate: 1000 800 31.9 g/m 2 /d 600 400 200 0 Uptake Rate: -1.33 g/m 2 /d Uptake Rate: -0.18 g/m 2 /d 0 100 200 300 400 500 Time, hours
Development of Models for N Removal and Duckweed Growth
Nutrient t (N) Transport Model Duckweed takes up N (NH + 4+ ) for its growth at water surface Sun Light Duckweed NH 4+ transfer from bulk to duckweed d at surface NH + 4 N transfer at surface = N uptake by duckweed Duckweed Pond
Model Development Governing Equation: c = D t z 2 c Boundary Conditions: c γ D ( z = L, t) = k c ( z = L, t) zz c ( z = 0, t ) = 0 z Initial Condition: c ( z, t = 0) = c 0 2 Boundary 1 L z Boundary 2 j z+δz j z Δz Mass Transport in Duckweed Pond
Pilot Tests in Outdoor Duckweed Tanks
Duckweed Preparation in Greenhouse
Outdoor Pilot Test Set-up Parameters: Temperature Light N concentration P concentration Duckweed mass
Pilot Test Results: Temperature and Light Intensity Te emperature, oc Light, umol/m 2 -s 35 30 25 20 15 10 5 0 1000 800 600 400 200 a b Summer Test Summer Test Fall Test Fall Test 0 6/12/00 7/10/00 8/7/00 9/4/00 10/2/00 10/30/00 Date
Pilot Test Results: Nutrient Removal and Duckweed dgrowth Fall Test TKN, mg/l Total P, mg/l g Duckwe eed (Dry), k 120 100 a 50% Dilution 25% Dilution 33% Dilution 20% Dilution Removal Rate: 80-2.03g/m 60 2 /d 40 20 0 40 30 20 10 0 1.0 0.8 0.6 b c Removal Rate: -0.40 g/m 2 /d 0.4 Growth Rate: 14.5 g/m 2 /d 0.2 0.0 0 10 20 30 40 50 60 Time, Days
Growing High-Starch Duckweed for Fuel Ethanol Production
Duckweed Growth Model utrient Co oncentratio on in Half Strength SAM, mg/l N 200 180 160 140 120 100 80 60 40 20 rate = -28.35 mgnh 3 -N/L/d R 2 = 0.999 rate = -7.72 mgpo 4-P/L/d R 2 = 0.979 TAN Orthophosphate Biomass 0 00 0.0 0 5 10 15 20 25 30 Time, d 2.5 20 2.0 15 1.5 10 1.0 05 0.5 eed Bioma ass, g Duckw
N and P Contents in Duckweed Biomass ntent in Bi iomass, mg/g 70 60 50 40 30 N Content in Full Strength SAM P Content in Full Strength SAM N Content in Half Strength SAM P Content in Half Strength SAM N min = 16.5 mg/g Nu utrient Co 20 10 P min = 6.3 mg/g 0 0 5 10 15 20 25 30 Time, d
Major Composition of Duckweed Grown on Animal Wastewater: t Proteins: 30-40% Starch: 15-18% Others: Fiber, Lipids, Carbohydrates, Minerals In a nutrient limiting environment: Proteins: Down Starch: Up
High-Starch Duckweed Duckweed Potato Slice 1 mm 45.8% starch (dry base)
Saccharification Reducing Sugars Production: 509 mg per gram of Dry Duckweed
Ethanol Fermentation Ethanol Yield: 258 mg per gram of Dry Duckweed Biomass
Summary Nutrient removal in duckweed system: N: 1.3-2.3 g/m 2 /d; P: 0.2 0.5 g/m 2 /d Duckweed growth gate: 15 30 g (dry)/m 2 /d Models for N removal and duckweed growth Starch content in dry Duckweed: ~46% Average annual starch production: 28 tons/hec/yr / Corn starch yield: ~5.0 tons/hec/yr Ethanol yield: 258 mg/g dry duckweed Easy for saccharification No need for additional nutrients in Fermentation
Duckweed Harvesting
Duckweed Harvesting
Pilot Duckweed Project
Acknowledgement Collaborators: Dr. B.A. Bergmann Dr. Y.T. Yamamoto Dr. J.J. Classen Dr. J.C. Barker Dr. J.J. J Ducoste Post-Docs: Dr. Louis Landesman Dr. Ye Chen Dr. Mike Yablonski Dr. Jiele Xu Dr. Weihua Cui Graduate Students: Sumate Chaiprapat Wayne Howard Ryan Smith Courtney Lyerly Deepak Keshewani David Hughes
Acknowledgement Funding Agencies: US Department of Agriculture North Carolina Agricultural Research Service North Carolina Biofuels Center NCSU Animal & Poultry Waste Management Center
Thank you!!? or!