air lift bioreactor

“BIOETHANOL FROM NON-CONVENTIONAL SOURCES”

José A. Teixeira

IBB - Institute for Biotechnology and Bioengineering, Centre of Biological Engineering University of Minho, PORTUGAL e-mail: [email protected]

Raw materials and processes currently used for bioethanol production

Sugarcane

Sugar beet

Sorghum

Cheese Whey

Brazil, India

Europe (France)

India

New Zealand

Milling for sugars extraction, and fermentation of sugars

United States, China, Canada

Corn

China, Canada, Europe

Wheat

ThailandCassava

Milling, liquefaction, saccharification, and fermentation of sugars

Bioethanol production worldwide

89%

40%

60%

Sugar crops Starch crops

Brazil: main exporter United States, Japan, Europe: main importers

Brazil Vehicles use ethanol in the pure form or in mixture with the gasoline, where ethanol corresponds up to 25% of the mixture

United States Ethanol is used in two forms: mixed with gasoline in the maximum proportion of 10%, or in mixtures containing 85% ethanol and 15% gasoline, as an alternative fuel

Bolivia Current blend levels are 10%, but efforts are being directed to expand ethanol blends to 25%

Thailand Gasoline must be blended with 10% ethanol

Colombia Requires 10% ethanol blends in cities with populations over 500,000

China Some regions of China use mixtures containing up to 10% ethanol in gasoline

India Addition of 5% ethanol to gasoline is mandatory. Efforts will be directed to increase the ethanol percentage in the mixture to 10%

Canada 5% of all motor vehicle must be ethanol or biodiesel

Sweden Mixtures containing 5% ethanol in gasoline are used

Japan The replacement of 3% of gasoline by ethanol is authorized, but efforts will be done to increase this value to 10%

Bioethanol consumption worldwide

Rice straw

Wheat straw

Sugarcane bagasse

CELLULOSE

HEMICELLULOSE

LIGNIN

Technology under development

Bioethanol production from non-conventional sources

Cellulose hydrolysis: concentrated acid hydrolysis and enzymatic hydrolysis

Pre-treatment: diluted acid hydrolysis

O

OH

OH

OHOH

O

OH

OH

OH

O

O O

OH

OH

OH

O O

OH

OH

OH

O O

OH

OH

OH

Cellobiose


Obtainment of a fermentable sugars solution

Fermentation of sugars Ethanol separation and purification

LIGNOCELLULOSIC BIOMASS

Distillation

EthanolMilling

Cellulose conversion (hydrolysis)

Pre-treatment

Fermentation

Fermentation

(Xylose)

(Glucose)


– Iogen (straw – Canada); Abengoa (straw – Spain, US); Etek (softwood – Sweden); Elsam (straw –Denmark); TMO (straw etc. –UK); Tavda (wood – Russia); NEDO (rice straw – Japan)

Challenges to be overcome for an efficient bioethanol production from lignocellulosic biomass

1) High energy consumption for biomass pretreatment

Cellulose fibers

(1)

(2)

(3)

2) Development of a suitable and economically viable hydrolysis process step

Specific enzymes

Glucose

CELLULOSE


3) Improvement in the conversion rate and yield of hemicellulose sugars

Ethanol

Toxic compounds:

low sugars conversion yield

fermentation

Pentoses (Xylose and Arabinose) and Hexoses


3) Other important considerations for the process implementation

To develop microorganisms able to metabolize pentose and hexose sugars simultaneously withstanding the stress imposed by the process inhibitors

To evaluate the process scalability

To perform an analysis of the costs involved for commercial production

To establish alternatives for the recovery of pretreatment chemicals and wastewater treatment


Sweet corn Jerusalem artichoke

Sweet potato

Sweet sorghum

Other energy crops

Carbohydrate and expected ethanol yields for sweet corn, Jerusalem artichoke, sweet potato ad sweet sorghum

Current ethanol yield from grain corn in the US and sugarcane in Brazil is approximately 3,500 and 6,000 L/ha, respectively.1

Carbohydrate and expected ethanol yields for sweet corn, Jerusalem artichoke, sweet potato ad sweet sorghum

Current ethanol yield from grain corn in the US and sugarcane in Brazil is approximately 3,500 and 6,000 L/ha, respectively.1

http://organic.kysu.edu/BiofuelCrops.shtml#Ref1

http://organic.kysu.edu/BiofuelCrops.shtml#Ref1

Sweet Sorghum as an energy crop

•It has a photosynthetic efficiency (~ 4 g biomass/MJ of solar radiation) two times or

more that of C3 crops (forest)

•It is able to grow anywhere in dry climates with high yields of fermentable sugars,

grains and lignocellulosics.

•In some regions it is possible to obtain two plantations per year reaching full maturity

and a large production.

•It has low water requirements 1/3 of sugar cane, 1/2 of corn, 1/4 of Short Rotation

Forestry.

•Sweet sorghum (Sorghum bicolor) is frequently called as smart crop for its ability

of not only produce food but fuel as well

Sweet Sorghum as an energy crop

•It has a photosynthetic efficiency (~ 4 g biomass/MJ of solar radiation) two times or

more that of C3 crops (forest)

•It is able to grow anywhere in dry climates with high yields of fermentable sugars,

grains and lignocellulosics.

•In some regions it is possible to obtain two plantations per year reaching full maturity

and a large production.

•It has low water requirements 1/3 of sugar cane, 1/2 of corn, 1/4 of Short Rotation

Forestry.

•Sweet sorghum (Sorghum bicolor) is frequently called as smart crop for its ability

of not only produce food but fuel as well

Agave vs sucarcane needs

Agave and sugar cane bioethanol production

Miscanthus x giganteus properties

•relatively high yields — 8-15 t/ha (3-6 t/acre) dry weight,

•low moisture content (as little as 15-20% if harvested in late winter or

spring),

•annual harvests, providing a regular yearly income for the grower,

•good energy balance and output/input ratio compared with some other

biomass options,

•low mineral content, especially with late winter or spring harvest, which

improves fuel quality.

•can be grown in a cool climate like that of northern Europe

Miscanthus x giganteus properties

•relatively high yields — 8-15 t/ha (3-6 t/acre) dry weight,

•low moisture content (as little as 15-20% if harvested in late winter or

spring),

•annual harvests, providing a regular yearly income for the grower,

•good energy balance and output/input ratio compared with some other

biomass options,

•low mineral content, especially with late winter or spring harvest, which

improves fuel quality.

•can be grown in a cool climate like that of northern Europe

• a typical acre of corn yields around 7.6 tons of input per acre and

756 gallons of ethanol..

• switchgrass, which yields around 3-6 tons of biomass and 400-900

gallons of ethanol fuel

•giant Miscanthus is capable of producing up to 20 tons of biomass

and 3,250 gallons of ethanol fuel

Miscanthus x giganteus ethanol production yield


CHEESE WHEY

Liquid remaining after the

precipitation and removal of milk casein during

cheese-making

Represents 85-95% of the milk volume and its

world production is estimated to be

over 108 tons/ year

Lactose (5-6% w/v) is assumed to be responsible

for 90% of the whey’s BOD and

COD.

Biological treatment by conventional

aerobic process is very expensive

Bioconversion of lactose to ethanol represents a process which can provide a value-added product from cheese manufacturing, allied with efficient bioremediation of plant effluent.


Obtainment of a fermentable sugars solution

Fermentation of sugars Ethanol separation and purification

CHEESE WHEY

Distillation

Ethanol

Fermentation

(Lactose)

Concentrated cheese whey or cheese whey powder solution

Direct fermentation of whey or whey permeate to ethanol is generally not economically feasible because the low lactose content results in low ethanol titre (2–3% v/v), making the distillation process too expensive.


Cheese whey concentration: by ultrafiltration and/or reverse osmosis processes.

Yeasts that ferment lactose: Kluyveromyces lactis, K. marxianus, Candida pseudotropicalis, genetically modified Saccharomyces cerevisiae.

Important process considerations:

8 million tons of lactose (worldwide annual whey production)

~50% not transformed into added-value

sub-products

~2.3 million m3 ethanol

considering a 85% conversion yield

Worldwide production of bioethanol for fuel in 2008: ~65 million m3

Whey to bioethanol…

Whey to Ethanol Industrial Plants

Ireland Carbery Milk ProductsCarbery Milk Products

since 1978, potable ethanol & ethanol for fuel (since 2005)

11 000 tons ethanol /year

New Zealand FonterraFonterra

Anchor Ethanol (Fonterra subsidiary)

potable ethanol & ethanol for fuel (since 2007)

17 million liters ethanol /year

United States Golden CheeseGolden Cheese

Land O’LakesLand O’Lakes

Germany Müllermilch Müllermilch

near Dresden; 10 million litres ethanol /year

from dairy by-products

Whey permeate biotechnological treatment

Flocculent Saccharomyces cerevisiae strains able to

metabolize lactose

Continuous high cell density systems

S. cerevisiae traditionally used in industry

Molecular biology techniques well developed

Good fermentative capacity

• Higher volumetric productivity

• Improvement of separation processes

• Higher stability

A Saccharomyces cerevisiae strain that efficiently metabolizes lactose was developed, with a lactose metabolization capacity comparable to the one presented by other natural lactose users

A high ethanol productivity (10 gl-1h-1) system using cheese whey as a substrate was developed

The developed fermentation system proved its long term stability

Pilot scale experiments validated the developed fermentation process

6-L Air-lift Bioreactor

Aerated at 0.1 vvm

pH 4.2 ± 0.2

Temperature: 30 ± 1 ºC 8% (v/v) ethanol (max.) – Ethanol productivity 0.7 gL-1 h-1

Fermentation of Cheese Whey powder solutions by T1-E

110–150 gL-1 Lactose + Corn Steep Liquor (10 gL-1)

Repeated-batch operation with biomass recycling by flocculation

Sun light

WaterWater

CO2

CO2

CO2

nutrientsnutrients

ETHANOL

O2O2

The microalgae Chlorella vulgaris, particularly, has been considered as a promising feedstock for bio-ethanol production


Microalgae cultivation

Cell rupture

Starch

Enzymatic

hydrolysissugars

Fermentation

ETHANOL

Some algal species are able to conduct self-fermentation

Technology under development


microalgae can be harvested batch-wise nearly all-year-round

they grow in aqueous media, but need less water than terrestrial crops, therefore

reducing the load on freshwater sources

the ability of microalgae to fix CO2

Advantages of this process:


Source Ethanol yield(gallons/acre)

Ethanol yield(L/ha)

Corn stover 112-150 1,050-1,400

Wheat 277 2,590

Cassava 354 3,310

Sweet sorghum 326-435 3,050-4,070

Corn 370-430 3,460-4,020

Sugar beet 536-714 5,010-6,680

Sugarcane 662-802 6,190-7,500

Switch grass 1,150 10,760

Microalgae 5,000-15,000 46,760-140,290

Bioethanol yield from different sources:


Conclusions

World ethanol production and consumption will continue to grow strongly

Corn is the main raw material used today, but in the future.....

Lignocellulose

MicroalgaeDon’t affect the food provision

Development of ethanol production systems all over the world

Cheese whey

Agave

air lift bioreactor

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