Using CO2 & Algae to Treat Wastewater and Produce Biofuel Feedstock

Transcription

1 Using CO2 & Algae to Treat Wastewater and Produce Biofuel Feedstock Tryg Lundquist Cal Poly State University John Benemann MicroBio Engineering First Western Forum on Water & Energy Sustainability Bren School, UCSB March 23, 2007

2 CO2 and Wastewater Treatment WW Treatment Technologies Scale of the Industry and Growth Algae s Role in WW Treatment CO2 s New Role Research at Cal Poly Future Work Actinastrum sp.

3 Major Wastewater Treatment Technologies in U.S. Activated Sludge 6,800 Facilities 25,000 million gallons per day 94,000 million liters per day MWh/MG Biofilm Systems 2,500 Facilities 6,000 million gallons per day 23,000 million liters per day MWh/MG

4 Major Technologies, Continued Conventional Ponds 5,100 Facilities 2,000 million gallons per day 8,000 million liters per day MWh/MG 0.3 MGD average flow per facility

5 Sun CO 2 Reclaimed CO 2 N Algae Water Waste Water P O 2 CO 2 N P Biomass Organics Bacteria

6 Effluent Quality: Conventional & C-limited High Rate Ponds Soluble BOD removal 80-95% Natural Disinfection 1-2 log removal per pond N removal 20% - 70% P removal 10% - 50%

7 Nutrient Removal: A Growing Need but Energy Intensive Nutrient Removal ,300 Facilities 6,000 million gallons per day 24,000 million liters per day 1.5 MWh/MG additional Nutrient Removal ,200 Facilities 15,000 million gallons per day 56,000 million liters per day Energy Savings Desirable

8 Conventional vs. High Rate Ponds Conventional Ponds Shallow (1 2 m) or Deep (4 6 m) No mechanical mixing day residence times High Rate Ponds Shallow (<1 m) Paddle wheel mixing MWh/MG (CO2 process) 3 7 day residence times

9 Algae for Wastewater Treatment Pros Produce oxygen with low energy input Remove soluble N and P CO2 fixed Biomass produced Cons Rarely settle well Failure to meet suspended solids limits Interfere with disinfection Biomass produced

10 Algae Harvesting Options Chemical Coagulation + Flotation Natural Settling

11 New Approach for Wastewater Treatment CO2-Enhanced High Rate Ponds

12 CO2-Enhanced High Rate Ponds Improved and accelerated treatment CO2 is fixed in algal biomass Fuel production from biomass provides greenhouse gas abatement Energy used in WW treatment decreases Fuel production residual becomes fertilizer

13 Add CO2 to balance C:N:P Algae: C : N : P = 50 : 8 : 1 Wastewater: C : N : P = 20 : 8 : 1

14 Add CO2 to balance C:N:P Algae: C : N : P = 50 : 8 : 1 Wastewater: C : N : P = 20 : 8 : 1 Add CO2

15 CO2 Abatement & Offset Estimate Biofuel Production (Methane) 0.4 tons per MG Energy Efficiency 1.2 tons per MG Fertilizer Manufacture Offset 0.3 tons per MG Total is potentially 1.9 tons per MG

16 Limits and Overall Potential Ponds not practical in many places 5-10 hectare per MG 0.8 millon tons CO2 fixed per year is estimated maximum for US

17 Cal Poly Research Batch & Semi- Continuous Cultures Extent and Rate of N and P Removal with CO2 Addition N Removal vs. Bioflocculation Cell Recycle Rate vs. Bioflocculation & Effluent Quality

18 Initial Wastewater Quality Primary Effluent 80 mg/l VSS 39 mg/l NH 4+ -N 5.4 mg/l PO P

19 Preliminary Results CO2 Enhanced 600 mg/l VSS <1 mg/l NH 4+ -N < 1 mg/l PO P Air Sparged 130 mg/l VSS 25 mg/l NH 4+ -N 3 mg/l PO P 5 Days Growth

20 Batch Growth Curves 0.7 Absorbance CO2 50%WW CO2 Media Air 50%WW CO2 10%WW Days of Incubation Mean of triplicates

21 Phase 2 Plans Pilot-Scale Research Multiple Ponds for Controlled Experiments Located at Existing Full-Scale Treatment Facility

22 Algae Biodiesel News (?) GREEN VALLEY March 4, 2007

23 Preliminary Findings: 10-30% oil, not 50% Water + MeOH 10x Cell Layer 100x Water + MeOH Algae Cells Chloroform + Lipid 10x Algae Methane Fermentation is Proven Oil Layer 40x

24 CO2 and Wastewater Treatment Ponds are a common & important treatment method Nutrient removal is in demand Algae Nutrient uptake Oxygen production Biofuel feedstock CO2 addition may: Improve nutrient uptake Accelerate treatment Decrease algae harvesting costs

25 Acknowledgements Graduate Students Adam Feffer Ian Woertz Professor Yarrow Nelson Cal Poly Funding US DOE SBIR Program Micractinium sp.

26 Questions? Tryg Lundquist California Polytechnic State University John Benemann MicroBio Engineering