Syngas fermentation for bio-fuels production

Syngas fermentation for bio-fuels production: Opportunities &

Summation

Presented By – Diksha Kumari

Mangalayatan university Aligarh

introduction

Time taking complex pre-treatment steps.

Low fermentibility of mixed sugar stream.

High enzyme cost.

Difficulty in utilization of whole

biomass.

Challenges in biochemical pathway

Synthetic gas or syngas is a mixture mainly composed of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2) and other by-products like tars, hydrocarbon, nitric oxide and ammonia.

syngas

Biochemical pathway Solution Syngas derived Biofuel

Utilization of the whole biomass including lignin. Elimination of complex pre-treatment steps and costly

enzymes. Higher specificity of the biocatalysts. Independence of the H2:CO ratio for bioconversion. Aseptic operation of syngas fermentation due to

generation of syngas at higher temperatures Biological catalysts are able to ferment syngas into

liquid fuel effectively(Heiskanen et al., 2007; Henstra et al.,2007).

Why syngas...

Gasification SyngasProcessing

Syngas Fermentation

SyncrudeRefining &Upgrading

X LG

Syngas processing

Ligno-cellulosicBiomass

Fuels&

Chemicals

Incomplete utilization of lignocellulosic biomass

Low gas liquid mass transfer.

Low productivity.

Sensitivity of microorganisms to environmental conditions

Gasification is required to overcome this hurdle.

Gasification of lignocellulosic biomass through partial

oxidation leads to the formation of gaseous mixture.

Biomass Gasification

2(-CH-) + O2 → 2CO + H2

Incomplete utilization of lignocellulosic biomass

Low gas liquid mass transfer.

Low productivity.

Sensitivity of microorganisms to environmental

conditions

Rate limiting step.

Gas liquid interface mass transfer is the major

resistance for gaseous substrate diffusion.

Leading to low substrate uptake by microbes.

Leading to low productivity.

GAS – LIQUID MASS TRANSFER

Poor solubility of gaseous substrates in liquid phase is coped up by –

Optimizing the bioreactor design. (Bredwell et al., 1999). Increasing the agitation speed of the impeller (Bredwell et

al., 1999). Smaller bubbles sizes. Increasing the gas–liquid interfacial area for efficient mass

transfer.

Solution to GAS – LIQUID MASS TRANSFER

Incomplete utilization of lignocellulosic biomass.

Poor solubility of gaseous substrates in liquid phase.

Low productivity.

Sensitivity of microorganisms to environmental conditions

The identification of new microbial isolates that would

broaden the product range of syngas.

Thermophiles that employ CO as a substrate for the

production of chemicals could be selected based on the

identification of hydrogenase & CO dehydrogenase.

employ genetic engineering in carboxydotroph microbes

to enhance the product range of syngas fermentation

Incomplete utilization of lignocellulosic biomass.

Poor solubility of gaseous substrates in liquid phase.

Low productivity.

Sensitivity of microorganisms to environmental conditions.

Temperature….

By providing optimum temperature (eg- 37- 40°C for

mesophilles & 55-80°C for thermopiles').

Increases microbial growth and substrate utilization .

Increases solubility of gaseous substrate in aqueous

medium. (Younesi et al., 2005).

Ph….. Important for optimal activity of microbial catalysts. Optimum pH ranges between 5.5 - 7.5 (depending

upon species) E.g.- C.ljungdahli - optimum Ph of 5.8 – 6.0. (Klasson

et al., 1993)

Downstream

Midstream

Upstream

CONCLUSION

Optimization

Upstream Processes - Strain development by metabolic engineering Use of inexpensive carbon substrate.

Midstream Process - Innovative fermentation strategies. Reduced environmental impact.

Downstream Process - In situ recovery & other cost effective recovery Geographically distributed supply source. Improve energy efficiency.

Conclusions

A Joint study sponsored by U. S. Department of Energy (USDOE) and U.S. Department of agriculture (USDA). 2005. Biomass as feedstock for a bio energy and bioproducts industry: The technical feasibility of a Billion-ton annual supply, Oak Ridge, Tennessee.

Bredwell, M.D., Srivastava, P., Worden, R.M., 1999. Reactor design issues for synthesis-gas fermentations. Biotechnology Progress 15, 834–844.

Bouaifi, M., Hebrard, G., Bastoul, D., Roustan, M., 2001. A comparative study of gas hold-up, bubble size, interfacial area and mass transfer coefficients in gas-liquid reactors and bubble columns. Chemical Engineering and Processing 40, 97–111.

References

Heiskanen, H., Virkajarvi, I., Viikari, L., 2007. The effects of syngas composition on the growth and product formation of Butyribacterium methylotrophicum. Enzyme and Microbial Technology 41, 362–367.

Klasson, K.T., Ackerson, C.M.D., Clausen, E.C., Gaddy, J.L., 1993. Biological conversion of coal and coal-derived synthesis gas. Fuel 72, 1673–1678.

Lee, K.C., Rittmann, B.E., 2001. Applying a novel autohydrogenotrophic hollow-fiber membrane biofilm reactor for denitrification of drinking water. Water Research 36, 2040–2052.

Younesi, H., Najafpour, G., Mohameda, A.R., 2005. Ethanol and acetate production from synthesis gas via fermentation processes using anaerobic bacterium, Clostridium ljungdahlii. Biochemical Engineering Journal 27, 110–119.