Bioethanol Production
of 1st and 2nd Generation
3rd REBEL Partner Meeting, 27 May 2010
Sara Helmberger
Upper Austrian University of Applied Sciences Research and Development Ltd, Campus Wels
Content
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Introduction
World-leading bioethanol producing countries
Bioethanol production of 1st and 2nd generation
Various possible feedstocks
Production and processing technologies
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Introduction
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Fossil fuels are responsible for 73 % of the CO2 production in the atmosphere
Extreme contribution to global warming
Interest in development of methods, reducing green house gases
Bioethanol as alternative to petroleum-derived transportation fuels
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Definition Bioethanol
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Ethyl alcohol, grain alcohol, CH3-CH2-OH or EtOH
= Liquid biofuel
Advantages,
compared to gasoline:
- higher octane number
- broader flammability limits
- higher flame speeds
- higher heats of vaporization
- higher compression ratio
- shorter burn time
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Disadvantages,
compared to gasoline:
- lower energy density
- its corrosiveness
- low flame luminosity
- lower vapor pressure
- miscibility with water
Possible feedstocks: plant oils, sugar beets, cereals, organic waste,
processed biomass
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World-leading
bioethanol producing countries
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World-wide production of fuel ethanol more than tripled from 2000 until now
About 60% of global bioethanol production are obtained from sugar cane
and 40% from other crops (e.g. maize)
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North American
Ethanol production
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The United States are with over 41 % the world´s leader in ethanol production
Feedstocks: maize
wheat, barley, sorghum
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South American
Ethanol prodution
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South America contributes with roughly 35 % to world´s ethanol production, with
Brazil being the leader country
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Feedstock: sugar cane
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~ 20 % exported to US, EU, others
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European
Ethanol production
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Europe contributes with 9 % to world´s ethanol production
-> Comparable to the US ethanol market of roughly ten years ago
Plants in France, Spain, Sweden, UK, Austria (Pischelsdorf, Lower Austria)
In 2000, the EU introduced a Biofuel Directive
Commission of the European Communities (2007) -> binding minimal target
of 10 % biofuels by 2020
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Feedstock: wheat, sugar beet, waste from the wine industry
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European
Ethanol production
Bioethanol Plant in Pischelsdorf, Lower Austria
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Production technology
Feedstocks
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Bioethanol production
of 1st generation
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Major feedstocks for world´s ethanol production:
Sugar-containing feedstock: Sugar cane
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Starchy feedstock: Maize
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Bioethanol production
of 1st generation
Starchy materials (e.g. maize)
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US: 2 types of maize processing facilities:
- Wet milling (since 1980s)
- Dry grind (newer technology)
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Starch = a polysaccharide carbohydrate,
with a large number of sugar-molecules
Break down of the chains of this carbohydrate to obtain the single (individual) sugars
-> Hydrolysis technique
Fermentation with microorganisms (e.g. yeasts)
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Bioethanol production
of 1st generation
Sugar-containing feedstocks
(e.g. sugar cane, beet molasses, sweet sorghum)
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provide the single sugars (e.g. sucrose, glucose and fructose), which can be readily
fermented by microorganisms (yeast) -> no hydrolysis is necessary
Brazil: sugar cane
- harvest
- pressing
- Fermentation of sugar juice by microorganisms (yeast)
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Europe: Beet molasses
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Developing countries (e.g. Africa): Sweet sorghum
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Bioethanol production
of 2nd generation
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Feedstocks: Alternative or lignocellulosic materials
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= non food crops:
- waste and remnant biomass
- stalks of wheat and corn
- wood
- grass
- straw
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These most abundant reproducible feedstocks on Earth are of
- high yields
- low costs
- good suitability for low quality land
- low environmental impacts
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Bioethanol production
of 2nd generation
Lignocellulosic biomass
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3 basic polymers:
- Cellulose
- Hemicelluloses
- Lignin
Processing of lignocellulosic material to bioethanol
1. Pre-treatment
3. Fermentation
2. Hydrolysis
4. Product separation
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Bioethanol production
of 2nd generation
Pre-treatment
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Size-reduction
Removal of structural and compositional impediments
-> Lignocellulosic biomass is made more accessible for subsequent hydrolysis
Pre-treatment possiblities:
- mechanical
- chemical
- biological pre-treatment
- “Steam Explosion”
Steam Explosion:
- Biomass is extruded at high temperature and pressure
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Bioethanol production
of 2nd generation
Pre-treatment: Steam Explosion
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Bioethanol production
of 2nd generation
Hydrolysis
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= Saccharification of lignocellulosic biomass
Cellulose and Hemicellulose have to be broken down into single (individual) sugar
molecules
Catalyst:
- dilute acid
- concentrated acid
- enzymes (so-called cellulases)
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Enzymatic hydrolysis
- Cellulases are produced from both fungi and bacteria
- Hydrolysis at mild conditions (50°C and pH 5.0)
- Effective cellulose and hemicellulose breakdown
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Bioethanol production
of 2nd generation
Fermentation
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The hydrolysate (mixed sugar-solution) is then fermented by microorganisms
(e.g. yeast)
The sugar-solution contains not only one kind of sugar, but several different kinds
-> Microorganisms are required, that can convert all sugars to high yields of EtOH
Most effective producer of bioethanol: Saccharomyces cerevisiae
- can ferment only one kind of sugar
- metabolic engineered strain or
adapted strain of yeast is required
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Bioethanol production
of 2nd generation
Product separation, Distillation
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Distillation
- Bioethanol is separated from water
- Ethanol is concentrated to about 95.6 %
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Value-added co-products (e.g. lactic acid)
- processing into plastics or other products
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Lignin
- usage in various value-added applications
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Bioethanol
usage
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Thank you for your attention !
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