CO2 Capture and Recycle Using Microalgae

Mark CrockerUniversity of Kentucky mark.crocker@uky.edu

Bioeconomy 2017Washington, DC, July 11-12

East Bend Station Demonstration Facility

Capacity: 650 megawattsLocation: Boone County, KYCommercial Date: 1981

650 MW Scrubbed Unit (SCR, FGD, ESP)

MAIN GOALS

• Define kinetics of process

– Monitor dissolved CO2 and O2 to determine photosynthetic rate

– Help size large system and next generation design

• Gain understanding of real capital and operating costs

– Minimize energy consumption

• Measure biomass composition to track heavy metalsand other flue gas constituents

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CO2 % NOx

ppmSO2 ppm

Average 8.9 53.4 28.0

Minimum 7.2 14.5 6.5

Max. 9.6 97.2 84.3

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“Cyclic Flow” Photobioreactor (1150 L) Installed at East Bend(2nd Generation PBR)

East Bend Algae ProductivitySummer 2015

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Algae productivity = 0.165 ± 0.057 g/(L.day), equivalent to ca. 35 g/(m2.day)

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y, g

/lit

er/d

ayFlue Gas Bottled CO2 PAR

Plant outage

Plant outage

M.H. Wilson, D.T. Mohler, J.G. Groppo, T. Grubbs, S. Kesner, E.M. Frazar, A. Shea, C. Crofcheck, M. Crocker, Appl. Petrochem. Res., 2016, 6, 279-293.

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ol/

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s)

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C)

, CO

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%)

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Tr CO2 IN CO2 OUT PAR

CO2 in versus CO2 outAv. CO2 capture efficiency during daylight hours = 44%

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NOx in versus NOx out

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Av. NOx removal efficiency = 41.5%

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SOx in versus SOx out

• Inlet SO2 = ca. 10-30 ppm

• 100% SO2 removal efficiency

• No accumulation of sulfate ions in culture medium over 5 month operating period

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Schematic of a section of the algae system consisting of 52 PBR modules, 4 settling tanks (ST), holding tanks (HT), and UV sterilizers (UV).

A schematic of the algae system (260 PBR modules; 260 individual feed tanks, feed pumps, and compressors; 20 individual settling tanks, holding tanks, and UV sterilizers)

• A life cycle assessment (LCA) was developed for an algae system based on UK’s cyclic flow PBR, mitigating 30% of the CO2 emitted by a 1 MW coal-fired power plant.

• Operation of the algae system included cumulative process requirements and energy consumption associated with algae cultivation, harvesting, dewatering, nutrient recycling, and water treatment.

Life Cycle Analysis

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-6.1E+04

7.6E+03

1.8E+031.2E+032.9E+03

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erical fertilizers

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missio

n fro

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rtilizer

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atme

nt (sterilizatio

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mp

ressor

Pu

mp

req

uire

me

nt (P

BR

system)

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O2

emissio

n (P

BR

system

)

MTC

O2

• CO2 emission associated with the gas compressor was 8.7 x 103 metric tons, due to the large amount of flue gas (4422 m3/h) being compressed at full capacity for 12 h per day.

• PBR feed pumps emitted a lesser amount of CO2 (1.9 x 103 metric tons) on account of the cyclic flow operation mode.

• The PBR system was able to capture 43% (2.6 x 104 metric tons) of the target CO2 emission (6.1 x 104

metric tons).

• The LCA results demonstrate that a PBR algae system can be considered as a CO2 capture technology.

POWER PLANT

Capacity 1 MW

CO2 emission 22.76 ton/day

CO2 capture 30 %

CO2 emission mitigated 6.83 ton/day

Operation 300 day/year

ALGAE

Strain Scenedesmus acutus

Growth rate 0.15 g/L/day

Culture density at harvest 0.8 g/L (dry weight)

Algae required for 30% CO2 capture 3.88 ton/day

Life Cycle Analysis:Results

SUMMARY

Techno-economic Analysis

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Heat rate(kg CO2/mw-hr)

Capacity(Megawatt)

kg CO2/yr

CO2 conversion /algae production

CAPEXPBR

DewateringInfrastructure

Etc.

OPEXEnergy

MaintenanceDewatering

NutrientsEtc.

X carb X protein X lipid

Utilization$/ (kg* year) (+)

Operating Days

SpeciesSunlight

(PAR/m^2)

kg algae/yr

$/ (kg* year) (-) EconomicFeasibility

UncertaintiesCO2 credit?

Local Economic Impact?

981

300

1 MW

212 kton/yr

Scenedesmus sp.1.78 ton CO2/ton algae

3,968,090 kg/yr

$ 1,703,935 / yr $1,769,317 /yr

$875 /ton

US Scenario (best case):• 30% CO2 capture• Algae productivity = 35 g/m2.day• 300 operating days/yr• 30 yr amortization

Base case: 1 MW coal-fired power plant Estimated min. algae production cost = $875/ton(biomass dewatered to 10-15 wt% solids)

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Techno-economic Analysis (cont.)

$0

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to

n b

iom

ass

g/ (m^2* Day)

$/ TON ALGAE

US 2017 PRC 2017

Decreased capital cost

• Asymptote relates to operating costs

• Cost in PRC lower due mainly to lower labor costs (PBR installation and operation)

Operating costs;note asymptote

Bioplastics ($400-1200?/ton)Animal Feed / Aquaculture ($400-700/ton)

Liquid Fuels (⁓$300/ton)

Human and Animal Feed Supplements

($800-$1200/ton)

NutraceuticalsCosmetics

Food Products

FDARegulated

Applications

Algal Biomass Utilization

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Product/extract Selling price Wt% in algae

β-carotene $300-3000/kg 14%

Astaxanthin $2500-7150/kg 3%

DHA (>70% Pure) ~$12,540/kg 7.8%

EPA (>70% Pure) ~$12,540/kg 4%

EPA

DHA

Astaxanthin

β-carotene

Increasing value

Increasing market

size

Lianhenghui Demonstration Project – Zhengzhou, China

May 18, 2016

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Lianhenghui Demonstration Project

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Acknowledgements

• KY Department of Energy Development and Independence

• Department of Energy: Fossil Energy (NETL)

• Department of Energy: U.S.-China Clean Energy Research Center

• Duke Energy

• Algix LLC

• Lianhenghui Investment Co. Ltd.

• The UK algae team:

Michael Wilson Dr. Jack GroppoDaniel Mohler Dr. Czarena CrofcheckStephanie Kesner Aubrey SheaThomas Grubbs Dr. Eduardo Santillan-JimenezRobert Pace Tonya MorganAnd….. ca. 35 undergraduates

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