n-Butanol Production from Engineered Cyanobacteria Abhivir Sandhu, Amir Meysami, Bowen Liu, Bryce Difley, David Gurr, Marc Caruth, Michael Chang, Sarah Rajani

CHBE 453 : Bio Group 3

FLUE GAS

Production Goal: 100 million gallons/year n-butanol at 98% purity

Plant Design

Environmental Impact

Economics

ABSORPTION CELL GROWTH PRODUCTION

NAOH

AIR

WATER

WATER

TREATMENT

PRODUCT SEPARATION

N-BUTANOL

Absorption Column

NaOH + CO2 —> HCO3- + Na+

CO2 is converted to HCO3-

to prevent the need for

sparging.

Carbon Source

8 % CO2 flue gas from a

natural gas power plant has low concentrations of growth limiting SOX and NOX.

Photobioreactors

8HCO3- + H2O —> 4CO3

2- +C4H9OH + 6O2

A common drawback of photobioreactors is the inability to deal with excess O2 production. Integrated degassers allow for O2 and n-butanol removal to prevent product inhibition. The gas is collected to recover the stripped n-butanol.

Bubble Column

Compressed air separates

n-butanol while eliminating the need to remove cells from

culture broth.

Pervaporator

Water/n-butanol forms an

azeotrope. Pervaporation

reduces the separation

equipment required

compared to ordinary

distillation

Recycle

Cells are concentrated through

centrifugation and sent back to the production photobioreactors. A purge stream prevents build-up of toxins.

Objectives

Motivation: Since 1990, CO2 emissions from fossil fuels have increased by 60%, greatly affecting the air quality. Cyanobacteria are unicellular organisms that fix CO2 and light to produce carbohydrates. In collaboration with Phytonix, we have developed an indus-trial process that produces n-butanol us-ing their engineered strain.

PURGE

Market Outlook: The current global demand of n-butanol is estimated at 8 billion USD and projected to reach 10 billion USD by 2020. Butanol can be used as an intermediate for a variety of chemicals, a solvent or fuel.

Economic Comparison: Equipment expenses for start-up are comparable to other methods of production. Although ABE fermentation requires a smaller initial investment, separation costs exceed the initial savings. Raw material cost for petro-chemical catalysis fluctuates heavily with propylene costs.

Annual Operating Expenses

Start-up Cost by Production Method

Global Butanol Demand

Current Established Regulations: There are currently no emission regulations designated by the EPA for n-butanol.

Existing Regulations:

Ontario Air Emission: 920 µg/m3 for a 24 hour emission average

New York State Water Quality Level: 50 µg/L

Preparing for Regulations: n-Butanol emission testing from the absorption column will be implemented. Treatment ponds for n-butanol removal from liquid waste and cell settling for sludge removal will be constructed. Possible sludge treatment applications include fertilizers or biogas production.

EPA n-Butanol Emission Regulation

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5

Draft Development July 1991

Agency Review

Science Consultation June 2011

External Review August 2011

Revise Assessment (yet to begin)

Flammable

Level Control LC

Liquid Hammer

Concentration

Hazard Assessment

$141.2 million USD/year