Production of Bioethanol Fuel

Samantha BrayUniversity of Winnipeg, Faculty of Biology.

Introduction• 1824-1826 Samuel Morey develops engine that runs on ethanol (Ethanol History, 2016).

•Why use ethanol?• Non-petroleum based – reduces dependence on crude oil.• Carbon neutral – reduced emissions contributing to

climate change.• Biomass used for conversion absorbs more CO2 then what

is released from production and burning. (Robson, 2007).• Produced from renewable resources, biodegradable, less

toxic. (University of Strathclyde Engineering, 2016).

Ethanol Biosynthesis (1st Generation)Sources: corn, sugarcane.

1. Milling - mechanical crushing of grains or corn to release starch/sugar components. • Wet Milling or Dry Milling.

2. Release fermentable sugars from biomass. • Hot water, enzymes (amylase and glucoamylase) or

acid treatments in batch or flow-through reactors.• Gelatinization, Liquefaction, and Saccharification

Summery of Corn to Ethanol Process Conditions

  Temperature

pH Time

Mashing ~60C ~6 5-10 mins

Liquefaction 70-80C ~6 2 hours

Saccharification

60-65C ~5 30 min

Fermentation 30-32C ~5 60-72 hours(NC State University, 2007).

Ethanol Biosynthesis (1st Generation)3. Fermentation of mash using yeast that convert sugar to

bioethanol and CO2.• End product is beer (~15% ethanol)

4. Distillation • 10-20% ethanol concentration 93% ethanol

concentration.

5. Rectification/Drying (dehydration of bioethanol).• Very important step in fuel bioethanol production as

water increases polarity of ethanol and when added to gasoline causes it to separate into two distinct phases.

• 93% ethanol concentration 99-99.7% ethanol concentration.

(NC State University, 2007).

(CropEnergies, n.d.)

Ethanol Biosynthesis (2nd Generation)1. Milling (Physical pre-treatment). (Onuki, 2008)2. Release fermentable sugars from biomass • Physico-chemical Pre-treatment• Steam explosion –260oC, 4.83 atmosphere, dilute acid

catalyst to break up biomass structure (Brodeur et al. 2011).• AFEX – Biomass + ammonia, 90oC, high pressure.• Ammonia penetrates cell walls, cleaves cross-linking

bonds.• Pressure release causes pore formation.

(NC State University, 2007).

• Biological Pre-treatment (NC State University, 2007). • Fungal treatment – Brown - white - soft-rot fungi can be

used to break down biomass.

Ethanol Biosynthesis (2nd Generation)• Chemical Pretreatment (NC State University, 2007). • Ozonolysis – Removes lignin and hemicellulose without

effecting structure of cellulose.• Acid Hydrolysis – Concentrated H2SO4 or HCl to

hydrolyze bonds.• Corrosive acids must be recovered from product after

treatment.• Alkaline Hydrolysis – NaOH breaks intercellular bonds

linking cellulose, hemicellulose and lignin.• Increases pore formation.

• Organic Solvents – High temperature organic solvents break down internal lignin bonds, ether and ester bonds, between lignin and hemicellulose. • Can use methanol, ethanol, acetone, glycerol.

Lignin

Hemicellulose

Cellulose

Schematic representation of the matrix of polymers that make up cellulose and the result of pre-treatment.

Pre-treatment

(Brodeaur et al. 2011)

Ethanol Biosynthesis (2nd Generation)

3. Saccharification (NC State University, 2007)• Enzymes used instead of acid/base hydrolysis to produce

glucose from cellulose.• Hemicellulose breaks down into pentose sugars (xylose).• Lignin is separated and removed.

4. Fermentation of cellulosic biomass to bioethanol (Brodeaur et al. 2011)• Work being done with genetically modified organisms to

ferment xylose along with glucose together.5. Distillation6. Rectification/Drying (dehydration of bioethanol).

Bioethanol Fuel• Renewable and climate friendly.

• The CO2 emitted is taken up into the plants used to make ethanol.

Bioethanol in E5: Standard petrol in Europe. Labelled as super or premium fuel at the pumps.Bioethanol in E10: most commonly blended gasoline. Standard fuel in all US states. Nicknames “gasohol”.Bioethanol in E85: Used in Flexible Fuel Vehicles (FFVs). FFVs can switch between running on conventional fuel or bioethanol-fuel blends depending on availability and price. Bioethanol in E100: Not advised for use in temperate regions. Gasoline improves cold-starting characteristics in winters of temperate regions.

64%

25%

5%3% 2% 1%

USA Brazil EUChina Canada Australia

Annual Ethanol Production Shares of the Six largest Fuel Ethanol Producing Countries/Regions in 2011.

(Crop Energies, 2016).

(Amarasekara, 2014)

Common Ethanol Fuel Mixtures

Future Considerations• Cellulosic fermentation to ethanol using microalgae.

(Wargacki et al., 2012)• Doesn’t require arable land, fertilizer, watering.• Doesn’t compete for production of food.• Doesn’t contain lignin – sugars can be processed by simple

milling and does not require pre-treatment (expensive and energy intensive).

• Work being conducted on finding use for lignin by-product. (Brosse et al., 2011) • Currently lignin used for burning to power the fermentation. • Use in biodegradable polyester blends (adds

mechanical/thermal stability).• Use as environmentally friendly wood adhesives and

corrosion inhibitors.

Literature Cited Amarasekara, A. (2014). Separation of Lignin in the Cellulosic Ethanol Process. In A. Amarasekara, Handbook of Cellulosic Ethanol (pp. 360-361). Hoboken, New Jersey: Scrivener Publishing.

Brodeur, G., Yau, E., Badal, K., & al., e. (2011, March 18). Chemical and Physicochemical Pretreatment of Lignocellulosic Biomass: A Review. Enzyme Research, pp. 1-17.

Brosse, N., Ibrahim, M., & Rahim, A. (2011, June 14). Biomass to Bioethanol: Initiatives of the Future for Lignin. ISRN Materials Science, pp. 1-10.

“Bioethanol” CropEnergies. n.d. Web. 18 March 2016. Retrieved from http://me1065.wikidot.com/ethanol-as-a-fuel-source.

“Bio-Ethanol Production Processes.” NC State University. 2007. Web. 12 March 2016. Retrieved from https://www.ncsu.edu/biosucceed/courses/documents/EtOHProd.pdf

Ethanol History. (2016, March 10). Ethanol History - From Alcohol to Car Fuel. Retrieved from Ethanol History: http://www.ethanolhistory.com/ Onuki, S. (2006). Bioethanol: Industrial production process and recent studies.

Robson, G. (2007). The History and Development of Bioethanol as an Alternative Fuel. Biotechnology .

Scheller, H., & Ulvskov, P. (2010, Januray 29). Hemicelluloses. Annual Review of Plant Biology, pp. 263-289.

University of Strathclyde Engineering. (2016, March 10). Biofuels for Transport. Retrieved from University of Strathclyde Engineering: http://www.esru.strath.ac.uk/EandE/Web_sites/02-03/biofuels/what_bioethanol.htm

Wargacki, A., Leonard, E., Win, M., & al., e. (2012, January 20). An Engineered Microbial Platform for Direct Biofuel Production from Brown Macroalgae. Science, pp. 308-313.